Dayton Power & Light 10-K 26 Feb 24 2023 FY Annual report Financial data

Cover Document

Cover Document $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) shares
Entity Information [Line Items]
Entity Voluntary Filers	Yes
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Registrant Name	DPL Inc.
Entity Incorporation, State or Country Code	OH
Entity File Number	1-9052
Entity Address, Address Line One	1065 Woodman Drive
Entity Address, City or Town	Dayton
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	45432
City Area Code	937
Local Phone Number	259-7215
Entity Tax Identification Number	31-1163136
Document Fiscal Period Focus	FY
Entity Public Float | $	$ 0
Entity Central Index Key	0000787250
Amendment Flag	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Common Stock, Shares Outstanding	1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Entity Voluntary Filers	Yes
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Registrant Name	THE DAYTON POWER AND LIGHT COMPANY
Entity Incorporation, State or Country Code	OH
Entity File Number	1-2385
Entity Address, Address Line One	1065 Woodman Drive
Entity Address, City or Town	Dayton
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	45432
City Area Code	937
Local Phone Number	259-7215
Entity Tax Identification Number	31-0258470
Document Fiscal Period Focus	FY
Entity Central Index Key	0000027430
Amendment Flag	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Common Stock, Shares Outstanding	41,172,173

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Auditor [Line Items]
Auditor Name	Ernst & Young LLP
Auditor Location	Indianapolis, Indiana
Auditor Firm ID	42
THE DAYTON POWER AND LIGHT COMPANY [Member]
Auditor [Line Items]
Auditor Name	Ernst & Young LLP
Auditor Location	Indianapolis, Indiana
Auditor Firm ID	42

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues	$ 861	$ 869	$ 672.7
OPERATING COSTS AND EXPENSES:
Net fuel cost	0	0.1	0.5
Utilities Operating Expense, Purchased Power	346.9	470.2	276.3
Utilities Operating Expense, Maintenance and Operations	232.1	184.7	152.4
Depreciation and amortization	82.1	80	76.1
Taxes, Miscellaneous	100.8	85.3	82.1
Gain (Loss) on Disposition of Business	0	0.6	0
Costs and Expenses	761.9	819.7	587.4
Operating Income (Loss)	99.1	49.3	85.3
OTHER (EXPENSE) / INCOME, NET:
Interest expense, net	(63.6)	(67.8)	(62.9)
Other income, net	6.8	4.2	0
Total other expense, net	(56.8)	(63.6)	(62.9)
INCOME / (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAX	42.3	(14.3)	22.4
Income tax expense / (benefit) from continuing operations	6.6	(9.6)	(0.5)
NET INCOME / (LOSS) FROM CONTINUING OPERATIONS	35.7	(4.7)	22.9
Loss from discontinued operations before income tax	0	0	(1)
Income tax benefit from discontinued operations	0	0	(0.2)
Net loss from discontinued operations	0	0	(0.8)
Net loss	35.7	(4.7)	22.1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenues	852	860.1	663.7
OPERATING COSTS AND EXPENSES:
Net fuel cost	0	0	0.5
Utilities Operating Expense, Purchased Power	346	469	275.1
Utilities Operating Expense, Maintenance and Operations	229.8	185.1	152.1
Depreciation and amortization	80.7	78.7	74.6
Taxes, Miscellaneous	100.6	85.1	81.9
Gain (Loss) on Disposition of Business	0	0.6	0
Costs and Expenses	757.1	817.3	584.2
Operating Income (Loss)	94.9	42.8	79.5
OTHER (EXPENSE) / INCOME, NET:
Interest expense, net	(25.8)	(28.8)	(24.2)
Other income, net	5.8	1.8	(2.5)
Total other expense, net	(20)	(27)	(26.7)
INCOME / (LOSS) FROM CONTINUING OPERATIONS BEFORE INCOME TAX	74.9	15.8	52.8
Income tax expense / (benefit) from continuing operations	13.5	(3.1)	5.7
Net loss	$ 61.4	$ 18.9	$ 47.1

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income/(Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
NET INCOME / (LOSS)	$ 35.7	$ (4.7)	$ 22.1
Derivative activity:
Reclassification of earnings, net of income tax benefit/(expense)	(0.8)	(0.8)	(0.8)
Unfunded pension and other postretirement activity:
Prior service cost for the period, net of income tax benefit/(expense)	(0.3)	0.1	0
Net loss for the period, net of income tax benefit/(expense)	(1.3)	2.1	6.4
Reclassification to earnings, net of income tax benefit/(expense)	0.2	1	1.9
Total change in unfunded pension obligation	(1.4)	3.2	8.3
Other comprehensive income / (loss)	(2.2)	2.4	7.5
Net comprehensive income / (loss)	33.5	(2.3)	29.6
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity	0.1	0	0
Income tax (expense)/benefit on net loss related to pension and postretirement activity	0.3	(0.7)	(1.8)
Tax expense (benefit)	(6.6)	9.6	0.5
Other comprehensive income before reclassifications	(1.6)	2.2
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Unfunded pension and other postretirement activity:
Other comprehensive income / (loss)	(1.4)	3.2
Other comprehensive income before reclassifications	(1.6)	2.2
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Unfunded pension and other postretirement activity:
Other comprehensive income / (loss)	(0.8)	(0.8)
Other comprehensive income before reclassifications	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Unfunded pension and other postretirement activity:
Tax expense (benefit)	0	(0.3)	(0.6)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Unfunded pension and other postretirement activity:
Tax expense (benefit)	0.2	0.2	0.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
NET INCOME / (LOSS)	61.4	18.9	47.1
Unfunded pension and other postretirement activity:
Prior service cost for the period, net of income tax benefit/(expense)	(0.3)	0.1	0
Net loss for the period, net of income tax benefit/(expense)	(1.2)	2.2	6.4
Reclassification to earnings, net of income tax benefit/(expense)	0.4	2.7	3.9
Total change in unfunded pension obligation	1.1	(5)	(10.3)
Other comprehensive income / (loss)	(1.1)	5	10.3
Net comprehensive income / (loss)	60.3	23.9	57.4
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity	0.1	0	0
Income tax (expense)/benefit on net loss related to pension and postretirement activity	0.4	(0.6)	(1.8)
Tax expense (benefit)	(13.5)	3.1	(5.7)
Other comprehensive income before reclassifications	(1.5)	2.3
THE DAYTON POWER AND LIGHT COMPANY [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Unfunded pension and other postretirement activity:
Tax expense (benefit)	$ (0.2)	$ (0.9)	$ (1.1)

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity	$ 0.1	$ 0	$ 0
Income tax (expense)/benefit on net loss related to pension and postretirement activity	0.3	(0.7)	(1.8)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity	0.1	0	0
Income tax (expense)/benefit on net loss related to pension and postretirement activity	$ 0.4	$ (0.6)	$ (1.8)

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 41	$ 30.5
Restricted cash	0.1	0.1
Accounts receivable, net	92.5	91.9
Inventories	44.5	26.8
Taxes applicable to subsequent years	113	94
Regulatory Assets, Current	56.6	39.2
Income Taxes Receivable, Current	8.9	10.9
Prepayments and other current assets	6.6	3.9
Total current assets	363.1	297.2
Property, plant and equipment:
Property, plant and equipment (Note 3)	2,521.9	2,193.6
Less: Accumulated depreciation and amortization	(535.1)	(505.7)
Property, plant and equipment, net of depreciation	1,986.8	1,687.9
Construction work in process	234.2	197.1
Total net property, plant and equipment	2,221	1,885
Other non-current assets:
Regulatory Assets, Noncurrent	155.7	129.8
Intangible assets, net of amortization	114	70.1
Other non-current assets	52.4	40.3
Total other non-current assets	322.1	240.2
Total assets	2,906.2	2,422.4
LIABILITIES AND SHAREHOLDER'S EQUITY
Current portion - long-term debt	15.2	155.2
Accounts payable	163.9	129.5
Accrued interest	16.9	16.1
Accrued taxes	101.6	88.4
Customer security deposits	12.7	16.7
Regulatory Liability, Current	18	40.4
Other current liabilities	22.6	20.9
Total current liabilities	350.9	467.2
Non-current liabilities:
Long-term debt	1,837.4	1,535.7
Deferred Income Tax Liabilities, Net	227.3	199
Taxes payable	113.4	94.5
Regulatory Liability, Noncurrent	182.1	198.7
Pension, retiree and other benefits	37.7	41.8
Other deferred credits	8.5	9.2
Total non-current liabilities	2,406.4	2,078.9
Liabilities	2,757.3	2,546.1
Commitments and contingencies
Common stock, shares outstanding	1	1
Common stock, shares authorized	1,500	1,500
Common shareholder's equity:
Common stock	$ 0	$ 0
Other paid-in capital	2,840.4	2,601.3
Accumulated other comprehensive income/(loss)	(4.6)	(2.4)
Retained earnings / (deficit)	(2,686.9)	(2,722.6)
Total common shareholder's equity	148.9	(123.7)
Total Liabilities and Shareholder's Equity	2,906.2	2,422.4
THE DAYTON POWER AND LIGHT COMPANY [Member]
Current assets:
Cash and cash equivalents	15.5	19.7
Restricted cash	0.1	0.1
Accounts receivable, net	93.1	92.3
Inventories	44.5	26.8
Taxes applicable to subsequent years	112.9	93.9
Regulatory Assets, Current	56.6	39.2
Income Taxes Receivable, Current	24.4	29.6
Prepayments and other current assets	8.1	4.2
Total current assets	355.1	305.7
Property, plant and equipment:
Property, plant and equipment (Note 3)	3,063.2	2,752.7
Less: Accumulated depreciation and amortization	(1,098.1)	(1,086.5)
Property, plant and equipment, net of depreciation	1,965.1	1,666.2
Construction work in process	230.8	195.3
Total net property, plant and equipment	2,195.9	1,861.5
Other non-current assets:
Regulatory Assets, Noncurrent	155.7	129.8
Intangible assets, net of amortization	111.4	68.5
Other non-current assets	52.9	40.4
Total other non-current assets	320	238.7
Total assets	2,871	2,405.9
LIABILITIES AND SHAREHOLDER'S EQUITY
Current portion - long-term debt	15.2	120.2
Accounts payable	163.8	129.5
Accrued interest	4.2	3.4
Accrued taxes	101.4	88.3
Customer security deposits	12.7	16.3
Regulatory Liability, Current	18	40.4
Other current liabilities	20.2	18.7
Total current liabilities	335.5	416.8
Non-current liabilities:
Long-term debt	1,012.3	712.5
Deferred Income Tax Liabilities, Net	206.1	194.9
Taxes payable	113.4	94.3
Regulatory Liability, Noncurrent	182.1	198.7
Pension, retiree and other benefits	37.7	41.8
Other deferred credits	4.7	5.1
Total non-current liabilities	1,556.3	1,247.3
Liabilities	1,891.8	1,664.1
Commitments and contingencies
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares outstanding	41,172,173	41,172,173
Common stock, shares authorized	50,000,000
Common shareholder's equity:
Common stock	$ 0.4	$ 0.4
Other paid-in capital	977.4	773.6
Accumulated other comprehensive income/(loss)	(27.9)	(26.8)
Retained earnings / (deficit)	29.3	(5.4)
Total common shareholder's equity	979.2	741.8
Total Liabilities and Shareholder's Equity	$ 2,871	$ 2,405.9

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Common stock, shares authorized	1,500	1,500
Common stock, shares outstanding	1	1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Common stock, shares authorized	50,000,000
Common stock, shares outstanding	41,172,173	41,172,173
Common stock, par value (in USD per share)	$ 0.01	$ 0.01

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
NET INCOME / (LOSS)	$ 35.7	$ (4.7)	$ 22.1
Adjustments to reconcile net income / (loss) to net cash provided by operating activities:
Depreciation and amortization	82.1	80	76.1
Deferred income taxes	26.2	(2)	4.7
Gain (Loss) on Disposition of Business	0	(0.6)	0
Gain (Loss) on Disposition of Business	0	0.6	0
Changes in certain assets and liabilities:
Accounts receivable, net	(0.6)	(20.4)	(2)
Inventories	(17.7)	(12.5)	(5.5)
Taxes applicable to subsequent years	(19)	(10.9)	(5.2)
Current and non-current regulatory assets and liabilities, net	(75.1)	38.4	10.3
Accounts payable	(19.7)	14	15.7
Accrued taxes payable / receivable	34.1	5.8	20.6
Accrued interest	0.8	0.8	(0.7)
Accrued pension and other postretirement obligations	(4.1)	(11.4)	(12.2)
Increase (Decrease) in Other Noncurrent Liabilities	(3.8)	(0.6)	0.6
Other	(6.9)	4.7	(3.6)
Net cash provided by operating activities	26.7	86.4	116.9
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(387.9)	(287.3)	(191.3)
Proceeds from disposal and sale of business interests	0	0.5	0
Payments for Removal Costs	0	(0.6)	(3.9)
Payments for (Proceeds from) Removal Costs	(26.8)	(22.4)	(17.2)
Other investing activities, net	0.2	(0.1)	(0.6)
Net cash used in investing activities	(414.5)	(309.9)	(213)
Cash flows from financing activities:
Deferred financing costs	(0.7)	(2.6)	(0.2)
Equity Contribution from Parent	239	0	132.5
Issuance of long-term debt	300	140	0
Borrowings from revolving credit facilities	315	255	120
Repayment of borrowings from revolving credit facilities	(455)	(165)	(155)
Net cash from financing activities	398.3	227.4	97.3
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	10.5	3.9	1.2
Cash and cash equivalents:
Restricted Cash and Cash Equivalents	41.1	30.6	26.7
Supplemental cash flow information:
Interest paid, net of amounts capitalized	71	62	59.3
Income taxes paid / (refunded), net	0	0	(17.5)
Non-cash financing and investing activities:
Accruals for capital expenditures	101.6	47	42.6
Non-cash capital contribution			132.5
Increase (Decrease) in Other Noncurrent Assets	(5.3)	5.8	(4)
THE DAYTON POWER AND LIGHT COMPANY [Member]
NET INCOME / (LOSS)	61.4	18.9	47.1
Adjustments to reconcile net income / (loss) to net cash provided by operating activities:
Depreciation and amortization	80.7	78.7	74.6
Deferred income taxes	9	(2.3)	4.5
Gain (Loss) on Disposition of Business	0	0.6	0
Changes in certain assets and liabilities:
Accounts receivable, net	0.7	20.5	1.9
Inventories	17.7	12.5	5.5
Taxes applicable to subsequent years	19	10.9	5.4
Current and non-current regulatory assets and liabilities, net	75.1	(38.4)	(10.3)
Accounts payable	(19.9)	13.6	15.1
Accrued taxes payable / receivable	37.3	12.5	10
Accrued interest	0.8	0.8	0
Accrued pension and other postretirement obligations	(4.1)	(11.4)	(12.2)
Increase (Decrease) in Other Noncurrent Liabilities	(3)	4.9	(1.8)
Other	9.4	(2.4)	(0.3)
Net cash provided by operating activities	35.4	117.6	130.2
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(384.3)	(283.7)	(189.3)
Payments for (Proceeds from) Removal Costs	(26.8)	(22.4)	(17.1)
Other investing activities, net	0.2	0.4	0.9
Net cash used in investing activities	(410.9)	(305.7)	(205.5)
Cash flows from financing activities:
Deferred financing costs	(0.7)	(2.6)	0
Equity Contribution from Parent	260	0	150
Issuance of long-term debt	300	140	0
Borrowings from revolving credit facilities	315	255	120
Repayment of borrowings from revolving credit facilities	(420)	(135)	(140)
Dividends paid on common stock to parent	(83)		(52)
Net cash from financing activities	371.3	193.4	78
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(4.2)	5.3	2.7
Cash and cash equivalents:
Restricted Cash and Cash Equivalents	15.6	19.8	14.5
Supplemental cash flow information:
Interest paid, net of amounts capitalized	34.4	15.9	21.2
Non-cash financing and investing activities:
Accruals for capital expenditures	101.5	47	42.5
Increase (Decrease) in Other Noncurrent Assets	$ (4.9)	$ 5.6	$ (4.9)

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Common stock, shares authorized	1,500	1,500
THE DAYTON POWER AND LIGHT COMPANY [Member]
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Other Paid-In Capital [Member]	Reclassification out of Accumulated Other Comprehensive Income [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Retained Earnings [Member]	Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Common Stock [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Other Paid-In Capital [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Accumulated Other Comprehensive Income/(Loss) [Member]	THE DAYTON POWER AND LIGHT COMPANY [Member] Retained Earnings [Member]
Other Comprehensive Income (Loss), Net of Tax	$ 7.5							$ 10.3
Balance at Dec. 31, 2020	(283.5)	$ 0	$ 2,468.8		$ (12.3)	$ (2,740)		616.7	$ 0.4	$ 714.4	$ (42.1)	$ (56)
Balance (in shares) at Dec. 31, 2020		1							41,172,173
Net loss	22.1							47.1
Common stock dividends								(42)		(42)		0
Equity Contribution from Parent	(132.5)		(132.5)					(150)		150
Other								(0.1)		(0.1)		0
Balance at Dec. 31, 2021	(121.4)	$ 0	2,601.3		(4.8)	(2,717.9)		782.2	$ 0.4	822.5	(31.8)	(8.9)
Balance (in shares) at Dec. 31, 2021		1							41,172,173
Non-cash capital contribution	132.5
Other Comprehensive Income (Loss), Net of Tax	2.4						$ (0.8)	5
Net loss	(4.7)							18.9
Common stock dividends								64		(49)		(15)
Equity Contribution from Parent	0							0
Other								0.3		(0.1)		0.4
Balance at Dec. 31, 2022	(123.7)	$ 0	2,601.3		(2.4)	(2,722.6)		741.8	$ 0.4	773.6	(26.8)	(5.4)
Balance (in shares) at Dec. 31, 2022		1							41,172,173
Other Comprehensive Income (Loss), Net of Tax	(2.2)						$ (0.8)	(1.1)
Net loss	35.7							61.4
Common stock dividends								(83)		(56.3)		(26.7)
Equity Contribution from Parent	(239)		(239)					(260)		260
Other	(0.1)		(0.1)	$ 0		0		(0.1)		(0.1)		0
Balance at Dec. 31, 2023	$ 148.9	$ 0	$ 2,840.4		$ (4.6)	$ (2,686.9)		$ 979.2	$ 0.4	$ 977.4	$ (27.9)	$ 29.3
Balance (in shares) at Dec. 31, 2023		1

Overview and Summary of Signifi

Overview and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Significant Accounting Policies [Line Items]
Business Description and Basis of Presentation	DPL, an indirectly wholly-owned subsidiary of AES, is a diversified regional energy company organized in 1985 under the laws of Ohio. DPL owns all of the outstanding common stock of DP&L, which does business as AES Ohio. Substantially all of DPL’s business consists of transmitting, distributing and selling of electric energy conducted through its principal subsidiary, AES Ohio. The terms “we”, “us”, “our” and “ours” are used to refer to DPL and its subsidiaries. AES Ohio is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, transmission and distribution services are still regulated. AES Ohio has the exclusive right to provide such service to its approximately 539,000 customers located in West Central Ohio. Principal industries located in AES Ohio’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. AES Ohio also provides retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000-square mile area of West Central Ohio. AES Ohio sources all of the generation for its SSO customers through a competitive bid process. AES Ohio's sales reflect the general economic conditions, seasonal weather patterns of the area, the market price of electricity and customer energy efficiency initiatives. AES Ohio owns numerous transmission facilities. AES Ohio records revenue and expenses for its proportional share of energy and capacity from its investment in OVEC. DPL’s other primary subsidiaries are MVIC and Miami Valley Lighting. MVIC is our captive insurance company that provides insurance services to AES Ohio and our other subsidiaries, and Miami Valley Lighting provides street and outdoor lighting services to customers in the Dayton region. In prior periods, AES Ohio Generation was also a primary subsidiary, selling all of its energy and capacity into the wholesale market. AES Ohio Generation retired and sold its only remaining operating asset in 2020. See Note 14. Discontinued Operations for more information. DPL's subsidiaries are all wholly-owned. DPL also has a wholly-owned business trust, DPL Capital Trust II, formed for the purpose of issuing trust capital securities to investors. AES Ohio’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators. Accordingly, AES Ohio applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs or overcollections of riders.
Overview and Summary of Significant Accounting Policies	OVERVIEW AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES DPL, an indirectly wholly-owned subsidiary of AES, is a diversified regional energy company organized in 1985 under the laws of Ohio. DPL owns all of the outstanding common stock of DP&L, which does business as AES Ohio. Substantially all of DPL’s business consists of transmitting, distributing and selling of electric energy conducted through its principal subsidiary, AES Ohio. The terms “we”, “us”, “our” and “ours” are used to refer to DPL and its subsidiaries. AES Ohio is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, transmission and distribution services are still regulated. AES Ohio has the exclusive right to provide such service to its approximately 539,000 customers located in West Central Ohio. Principal industries located in AES Ohio’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. AES Ohio also provides retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000-square mile area of West Central Ohio. AES Ohio sources all of the generation for its SSO customers through a competitive bid process. AES Ohio's sales reflect the general economic conditions, seasonal weather patterns of the area, the market price of electricity and customer energy efficiency initiatives. AES Ohio owns numerous transmission facilities. AES Ohio records revenue and expenses for its proportional share of energy and capacity from its investment in OVEC. DPL’s other primary subsidiaries are MVIC and Miami Valley Lighting. MVIC is our captive insurance company that provides insurance services to AES Ohio and our other subsidiaries, and Miami Valley Lighting provides street and outdoor lighting services to customers in the Dayton region. In prior periods, AES Ohio Generation was also a primary subsidiary, selling all of its energy and capacity into the wholesale market. AES Ohio Generation retired and sold its only remaining operating asset in 2020. See Note 14. Discontinued Operations for more information. DPL's subsidiaries are all wholly-owned. DPL also has a wholly-owned business trust, DPL Capital Trust II, formed for the purpose of issuing trust capital securities to investors. AES Ohio’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators. Accordingly, AES Ohio applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs or overcollections of riders. Financial Statement Presentation DPL’s Consolidated Financial Statements include the accounts of DPL and its wholly-owned subsidiaries, except for DPL Capital Trust II, which is not consolidated consistent with the provisions of GAAP. All material intercompany accounts and transactions are eliminated in consolidation. We have evaluated subsequent events through the date this report was issued. Reclassifications Certain amounts from prior periods have been reclassified to conform to the current period presentation. Use of Management Estimates The preparation of consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities and the revenue and expenses of the periods reported. Actual results could differ from these estimates and assumptions. Significant items subject to such estimates and assumptions include: the carrying value of Property, plant and equipment; unbilled revenue; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; reserves recorded for income tax exposures; litigation; contingencies; and assets and liabilities related to employee benefits. Cash and Cash Equivalents Cash and cash equivalents are stated at cost, which approximates fair value. All highly liquid short-term investments with original maturities of three months or less are considered cash equivalents. Restricted Cash Restricted cash includes cash which is restricted as to withdrawal or usage. The nature of the restrictions includes restrictions imposed by agreements related to deposits held as collateral. The following table summarizes cash, cash equivalents and restricted cash amounts reported within the Consolidated Balance Sheets that reconcile to the total of such amounts as shown on the Consolidated Statements of Cash Flows: December 31, $ in millions 2023 2022 Cash and cash equivalents $ 41.0 $ 30.5 Restricted cash (included in Prepayments and other current assets ) 0.1 0.1 Total cash, cash equivalents and restricted cash $ 41.1 $ 30.6 Accounts Receivable and Allowance for Credit Losses The following table summarizes accounts receivable as of December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Accounts receivable, net Customer receivables $ 71.0 $ 61.3 Unbilled revenue 19.4 24.0 Amounts due from affiliates 0.8 3.2 Other 2.2 3.9 Allowance for credit losses (0.9) (0.5) Total accounts receivable, net $ 92.5 $ 91.9 The following table is a rollforward of our allowance for credit losses related to the accounts receivable balances for the years ended December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Allowance for credit losses: Beginning balance $ 0.5 $ 0.3 Current period provision 5.4 2.5 Write-offs charged against allowance (6.0) (4.1) Recoveries collected 1.0 1.8 Ending balance $ 0.9 $ 0.5 The allowance for credit losses primarily relates to utility customer receivables, including unbilled amounts. Expected credit loss estimates are developed by disaggregating customers into those with similar credit risk characteristics and using historical credit loss experience. In addition, we also consider how current and future economic conditions are expected to impact collectability. Amounts are written off when reasonable collections efforts have been exhausted. Inventories Inventories are carried at average cost, net of reserves, and consist of materials and supplies used for utility operations. Regulatory Accounting As a regulated utility, AES Ohio applies the provisions of ASC 980 - Regulated Operations , which gives recognition to the ratemaking and accounting practices of the PUCO and the FERC. Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates. Regulatory assets can also represent performance incentives permitted by the regulator. Regulatory assets have been included as allowable costs for ratemaking purposes, as authorized by the PUCO or established regulatory practices. Regulatory liabilities generally represent obligations to make refunds or future rate reductions to customers for previous over collections or the deferral of revenue collected for costs that AES Ohio expects to incur in the future. The deferral of costs (as regulatory assets) is appropriate only when the future recovery of such costs is probable. In assessing probability, we consider such factors as specific orders from the PUCO or the FERC, regulatory precedent and the current regulatory environment. To the extent recovery of costs is no longer deemed probable, related regulatory assets would be required to be expensed in current period earnings. Our regulatory assets and liabilities have been created pursuant to a specific order of the PUCO or the FERC or established regulatory practices, such as other utilities under the jurisdiction of the PUCO or the FERC being granted recovery of similar costs. It is probable, but not certain, that these regulatory assets will be recoverable, subject to approval by the PUCO or the FERC. Regulatory assets and liabilities are classified as current or non-current based on the term in which recovery is expected. See Note 2. Regulatory Matters for more information. Property, Plant and Equipment New property, plant and equipment additions are stated at cost. For regulated transmission and distribution property, cost includes direct labor and material, allocable overhead expenses and AFUDC. AFUDC represents the cost of borrowed funds and equity used to finance regulated construction projects. Capitalization of AFUDC and interest ceases at either project completion or at the date specified by regulators. For substantially all depreciable property, when a unit of property is retired, the original cost of that property, less any salvage value, is charged to Accumulated depreciation and amortization , consistent with composite depreciation practices. Depreciation expense is calculated using the straight-line method, which allocates the cost of property over its estimated useful life. For DPL’s transmission and distribution assets, straight-line depreciation is applied monthly on an average composite basis using group rates that approximated 3.2% in 2023, 3.3% in 2022 and 3.7% in 2021. Depreciation expense was $78.0 million, $76.7 million and $72.9 million for the years ended December 31, 2023, 2022 and 2021, respectively. Depreciation and amortization expense in the Consolidated Statements of Operations is presented net of regulatory deferrals of depreciation expense and also includes amortization of intangible assets and amortization of previously deferred regulatory costs. AFUDC In accordance with the Uniform System of Accounts prescribed by FERC, AES Ohio capitalizes an allowance for the net cost of funds (interest on borrowed funds and a reasonable rate of return on equity funds) used for construction purposes during the period of construction with a corresponding credit to income. AFUDC equity and AFUDC debt were as follows for the years ended December 31, 2023, 2022 and 2021: Years ended December 31, $ in millions 2023 2022 2021 AFUDC equity $ 5.0 $ 5.7 $ 2.1 AFUDC debt $ 6.5 $ 1.3 $ 1.6 Impairment of Long-lived Assets GAAP requires that we test long-lived assets for impairment when indicators of impairment exist. If an asset is deemed to be impaired, we are required to write down the asset to its fair value with a charge to current earnings. The net book value of our property, plant, and equipment was $2,221.0 million and $1,885.0 million as of December 31, 2023 and 2022, respectively. We do not believe any of these assets are currently impaired. In making this assessment, we consider such factors as: the overall condition and distribution capacity of the assets; the expected ability to recover additional expenditures in the assets; and the anticipated demand and relative pricing of retail electricity in our service territory. Intangible Assets Intangibles include software and renewable energy credits. Renewable energy credits are carried on a weighted average cost basis and amortized as they are used or retired. Finite-lived intangible assets include capitalized software amortized on a straight-line basis over their estimated useful lives. These capitalized software intangible assets have a seven year-weighted average amortization period. The following table presents information related to the Company's capitalized software balances, including the gross amount capitalized and related amortization: December 31, $ in millions 2023 2022 Capitalized software $ 146.5 $ 105.0 Accumulated amortization $ (32.5) $ (36.1) Years ended December 31, 2023 2022 2021 Amortization expense $ 4.1 $ 3.3 $ 3.2 Estimated future amortization Years ending December 31, 2024 $ 6.3 2025 6.3 2026 5.9 2027 5.3 2028 4.9 Total $ 28.7 Implementation Costs Related to Software as a Service DPL has recorded prepayments for implementation costs related to software as a service in support of utility customer services of $14.8 million and $12.5 million as of December 31, 2023 and 2022, respectively, which are recorded within Other non-current assets on the accompanying Consolidated Balance Sheets. Debt Issuance Costs Costs incurred in connection with the issuance of long-term debt are deferred and presented as a direct reduction from the face amount of that debt and amortized over the related financing period using the effective interest method. Debt issuance costs related to a line-of-credit or revolving credit facility are deferred and presented as an asset and amortized over the related financing period. Make-whole payments in connection with early debt retirements are classified as cash flows from financing activities. Contingencies DPL accrues for loss contingencies when the amount of the loss is probable and estimable. We are subject to various environmental regulations and are involved in certain legal proceedings. If DPL’s actual environmental and/or legal obligations are different from our estimates, the recognition of the actual amounts may have a material impact on our results of operations, financial condition and cash flows; although that has not been the case during the periods covered by this report. Accruals for loss contingencies were not material as of December 31, 2023 and 2022. See Note 10. Contractual Obligations, Commercial Commitments and Contingencies for additional information. Financial Instruments Our Master Trust investments in debt and equity financial instruments of publicly traded entities are classified as equity investments. These equity securities are carried at fair value and unrealized gains and losses on these securities are recorded in Other income . As these financial instruments are held to be used for the benefit of employees or former employees participating in employee benefit plans and are not used for general operating purposes, they are recorded within Other non-current assets on the accompanying Consolidated Balance Sheets. See Note 4. Fair Value for more information. Financial Derivatives We have contracts involving the physical delivery of energy. These contracts qualify for the normal purchases and normal sales scope exception in ASC 815 - Derivatives and Hedging , thus we have elected to account for them as accrual contracts, which are not adjusted for changes in fair value. We have, in the past, used interest rate hedges to manage the interest rate risk of our variable rate debt. We used cash flow hedge accounting when the hedge or a portion of the hedge was deemed to be highly effective, which resulted in changes in fair value being recorded within accumulated other comprehensive loss, a component of shareholder’s equity / (deficit). We elected not to offset net derivative positions in the consolidated financial statements. Accordingly, we did not offset such derivative positions against the fair value of amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral under master netting agreements. See Note 5. Derivative Instruments and Hedging Activities for more information. Accumulated other comprehensive loss The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2023, 2022 and 2021 are as follows: Details about AOCL Components Affected line in the Consolidated Statements of Operations Years ended December 31, $ in millions 2023 2022 2021 Gains and losses on cash flow hedges (Note 5): Interest expense, net $ (1.0) $ (1.0) $ (1.0) Income tax effect 0.2 0.2 0.2 Net of income taxes (0.8) (0.8) (0.8) Amortization of unfunded pension and other postretirement obligations (Note 8): Other expense 0.2 1.3 2.5 Income tax effect — (0.3) (0.6) Net of income taxes 0.2 1.0 1.9 Total reclassifications for the period, net of income taxes $ (0.6) $ 0.2 $ 1.1 The changes in the components of Accumulated other comprehensive loss during the years ended December 31, 2023 and 2022 are as follows: $ in millions Gains / (losses) on cash flow hedges Change in unfunded pension and other postretirement obligations Total Balance at January 1, 2022 $ 12.8 $ (17.6) $ (4.8) Other comprehensive income before reclassifications — 2.2 2.2 Amounts reclassified from accumulated other comprehensive loss to earnings (0.8) 1.0 0.2 Net current period other comprehensive income / (loss) (0.8) 3.2 2.4 Balance at December 31, 2022 12.0 (14.4) (2.4) Other comprehensive loss before reclassifications — (1.6) (1.6) Amounts reclassified from accumulated other comprehensive loss to earnings (0.8) 0.2 (0.6) Net current period other comprehensive loss (0.8) (1.4) (2.2) Balance at December 31, 2023 $ 11.2 $ (15.8) $ (4.6) Insurance and Claims Costs In addition to insurance obtained from third-party providers, MVIC, a wholly-owned captive subsidiary of DPL, provides insurance coverage solely to us and our subsidiaries for workers’ compensation, general liability and property damage on an ongoing basis. Insurance and claims costs associated with MVIC include estimated liabilities of approximately $1.8 million and $1.6 million at December 31, 2023 and 2022, respectively, within Accrued and other current liabilities on the accompanying Consolidated Balance Sheets. DPL has estimated liabilities for medical, life, disability and other reserves for claims costs below certain coverage thresholds of third-party providers of approximately $8.0 million and $7.8 million at December 31, 2023 and 2022, respectively, within Accrued and other current liabilities and Other non-current liabilities on the accompanying Consolidated Balance Sheets. The estimated liabilities for workers’ compensation, medical, life and disability costs at DPL are actuarially determined using certain assumptions. There is uncertainty associated with these loss estimates, and actual results may differ from the estimates. Modification of these loss estimates based on experience and changed circumstances is reflected in the period in which the estimate is re-evaluated. Revenue Recognition Revenue is recognized from retail and wholesale electricity sales and electricity transmission and distribution delivery services. Revenue is recognized upon transfer of control of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. Energy sales to customers are based on the reading of their meters that occurs on a systematic basis throughout the month. We recognize the revenue on our Consolidated Statements of Operations using an accrual method for retail and other energy sales that have not yet been billed, but where electricity has been consumed. This is termed “unbilled revenue” and is a widely recognized and accepted practice for utilities. At the end of each month, unbilled revenue is determined by the estimation of unbilled energy provided to customers since the date of the last meter reading, estimated line losses, the assignment of unbilled energy provided to customer classes and the average rate per customer class. For more information, see Note 13. Revenue . Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities AES Ohio collects certain excise taxes levied by state or local governments from its customers. AES Ohio’s excise taxes and certain other taxes are accounted for on a net basis and recorded as a reduction in revenue in the accompanying Consolidated Statements of Operations. The amounts of such taxes were as follows: Years ended December 31, $ in millions 2023 2022 2021 Excise taxes collected $ 46.6 $ 49.2 $ 48.7 Repair and Maintenance Costs Costs associated with maintenance activities are recognized at the time the work is performed. These costs, which include labor, materials and supplies and outside services required to maintain equipment and facilities, are capitalized or expensed based on defined units of property. Pension and Postretirement Benefits We recognize in our Consolidated Balance Sheets an asset or liability reflecting the funded status of pension and other postretirement plans with current-year changes from actuarial gains or losses related to our regulated operations, which would otherwise be recognized in AOCL, recorded as a regulatory asset as this can be recovered through future rates. Such changes that are not related to our regulated operations are recognized in AOCL. All plan assets are recorded at fair value. We follow the measurement date provisions of the accounting guidance, which require a year-end measurement date of plan assets and obligations for all defined benefit plans. We account for and disclose pension and postretirement benefits in accordance with the provisions of GAAP relating to the accounting for pension and other postretirement plans. These GAAP provisions require the use of assumptions, such as the discount rate for liabilities and long-term rate of return on assets, in determining the obligations, annual cost and funding requirements of the plans. Consistent with the requirements of ASC 715 - Compensation - Retirement Benefits , we apply a disaggregated discount rate approach for determining service cost and interest cost for our defined benefit pension plans and postretirement plans. See Note 8. Benefit Plans for more information. Income Taxes Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the consolidated financial statement carrying amounts of the existing assets and liabilities and their respective income tax bases. We establish an allowance when it is more likely than not that all or a portion of a deferred tax asset will not be realized. Our tax positions are evaluated under a more likely than not recognition threshold and measurement analysis before they are recognized for consolidated financial statement reporting. Uncertain tax positions have been classified as noncurrent income tax liabilities unless expected to be paid within one year. Our policy for interest and penalties is to recognize interest and penalties as a component of the provision for income taxes in the Consolidated Statements of Operations. Income taxes payable, which are includable in allowable costs for ratemaking purposes in future years, are recorded as regulatory assets or liabilities with a corresponding deferred tax liability or asset. Investment tax credits that reduced federal income taxes in the years they arose have been deferred and are being amortized to income over the useful lives of the properties in accordance with regulatory treatment. See Note 2. Regulatory Matters for more information. DPL and its subsidiaries file U.S. federal income tax returns as part of the consolidated U.S. income tax return filed by AES. The consolidated tax liability is allocated to each subsidiary based on the separate return method as specified in our tax allocation agreement, and which provides a consistent, systematic and rational approach. See Note 7. Income Taxes for more information. Related Party Transactions In the normal course of business, DPL enters into transactions with related parties. All material intercompany accounts and transactions are eliminated in DPL’s Consolidated Financial Statements. See Note 11. Related Party Transactions for more information. In addition to the obligations under the note payable mentioned above, DPL also agreed to a security obligation, which represents a full and unconditional guarantee of payments to the capital security holders of the Master Trust. Discontinued Operations Discontinued operations reporting occurs only when the disposal of a business or a group of assets represents a strategic shift that has (or will have) a major effect on our operations and financial results. We report financial results for discontinued operations separately from continuing operations to distinguish the financial impact of disposal transactions from ongoing operations. Prior period amounts in the Consolidated Statements of Operations and Consolidated Balance Sheets are retrospectively revised to reflect the businesses determined to be discontinued operations. The cash flows of businesses that are determined to be discontinued operations are included within the relevant categories within operating, investing and financing activities on the face of the Consolidated Statements of Cash Flows. Transactions between the businesses determined to be discontinued operations and businesses that are expected to continue to exist after the disposal are not eliminated to appropriately reflect the continuing operations and balances held-for-sale. The results of discontinued operations include any gain or loss recognized on closing or adjustment of the carrying amount to fair value. See Note 14. Discontinued Operations for further information. New accounting pronouncements The following table provides a brief description of recent accounting pronouncements that could have an impact on our consolidated financial statements. Accounting pronouncements not listed below were assessed and determined to be either not applicable or did not have a material impact on our Consolidated Financial Statements. ASU Number and Name Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Issued But Not Yet Effective 2023-06 Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative In U.S. Securities and Exchange Commission (SEC) Release No. 33-10532, Disclosure Update and Simplification, issued August 17, 2018, the SEC referred certain of its disclosure requirements that overlap with, but require incremental information to, generally accepted accounting principles (GAAP) to the FASB for potential incorporation into the Codification. The amendments in this Update are the result of the Board’s decision to incorporate into the Codification 14 of the 27 disclosures referred by the SEC. The amendments in this Update represent changes to clarify or improve disclosure and presentation requirements of a variety of Topics. Many of the amendments allow users to more easily compare entities subject to the SEC’s existing disclosures with those entities that were not previously subject to the SEC’s requirements. Also, the amendments align the requirements in the Codification with the SEC’s regulations. The effective date for each amendment will be the date on which the SEC's removal of that related disclosure becomes effective, with early adoption prohibited. The amendments in this Update should be applied prospectively We will provide the required disclosures on a prospective basis on the date each amendment becomes effective. We do not expect ASU 2023-06 will have any impact on our Consolidated Financial Statements. 2023-07 Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures The amendments in this section are designed to improve the disclosures related to Segment reporting on an interim and annual basis. Public companies must disclose significant segment expenses and an amount for other segment items. This will also require that a company disclose its annual disclosures under Topic 280 in each interim period. Furthermore, companies will need to disclose the Chief Operating Decision Maker (CODM) and how the CODM assesses the performance of a segment. Lastly, public companies that have a single reportable segment must report the required disclosures under topic 280. The amendments in this Update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our Consolidated Financial Statements. 2023-09 Income Taxes (Topic 740): Improvements to Income Tax Disclosures The amendments in this Update require that public business entities on an annual basis (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. Furthermore, companies are required to disclose a disaggregated amount of income taxes paid at a federal, state, and foreign level as well as a break down of income taxes paid in an jurisdiction that comprises 5% of a company's total income taxes paid. Lastly, this ASU requires that companies disclose income (loss) from continuing operations before income tax at a domestic and foreign level and that companies disclose income tax expense from continuing operations on a federal, state, and foreign level. The amendments in this Update are effective for fiscal years beginning after December 15, 2024 We are currently evaluating the impact of adopting the standard on our Consolidated Financial Statements.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Overview and Summary of Significant Accounting Policies	OVERVIEW AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES DP&L, which does business as AES Ohio, is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, transmission and distribution services are still regulated. AES Ohio has the exclusive right to provide such service to its approximately 539,000 customers located in West Central Ohio. Principal industries located in AES Ohio’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. AES Ohio also provides retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000 square mile area of West Central Ohio. AES Ohio sources all of the generation for its SSO customers through a competitive bid process AES Ohio's sales reflect the general economic conditions, seasonal weather patterns of the area, the market price of electricity and customer energy efficiency initiatives. AES Ohio owns numerous transmission facilities. AES Ohio records revenue and expenses for its proportional share of energy and capacity from its investment in OVEC. AES Ohio has only one reportable segment, the Utility segment. In addition to AES Ohio's electric transmission and distribution businesses, the Utility segment includes revenue and costs associated with AES Ohio's investment in OVEC. The terms “we,” “us,” “our” and “ours” are used to refer to AES Ohio. AES Ohio’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators. Accordingly, AES Ohio applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs or overcollections of riders. Financial Statement Presentation AES Ohio does not have any subsidiaries. We have evaluated subsequent events through the date this report was issued. Reclassifications Certain amounts from prior periods have been reclassified to conform to the current period presentation. Use of Management Estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities and the revenue and expenses of the periods reported. Actual results could differ from these estimates and assumptions. Significant items subject to such estimates and assumptions include: the carrying value of Property, plant and equipment; unbilled revenue; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; reserves recorded for income tax exposures; litigation; contingencies; and assets and liabilities related to employee benefits. Cash and Cash Equivalents Cash and cash equivalents are stated at cost, which approximates fair value. All highly liquid short-term investments with original maturities of three months or less are considered cash equivalents. Restricted Cash Restricted cash includes cash which is restricted as to withdrawal or usage. The nature of the restrictions includes restrictions imposed by agreements related to deposits held as collateral. The following table summarizes cash, cash equivalents and restricted cash amounts reported within the Balance Sheets that reconcile to the total of such amounts as shown on the Statements of Cash Flows: December 31, $ in millions 2023 2022 Cash and cash equivalents $ 15.5 $ 19.7 Restricted cash (included in Prepayments and other current assets ) 0.1 0.1 Total cash, cash equivalents and restricted cash $ 15.6 $ 19.8 Accounts Receivable and Allowance for Credit Losses The following table summarizes accounts receivable as of December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Accounts receivable, net Customer receivables $ 70.0 $ 60.6 Unbilled revenue 19.4 24.0 Amounts due from affiliates 2.4 4.4 Other 2.2 3.8 Allowance for credit losses (0.9) (0.5) Total accounts receivable, net $ 93.1 $ 92.3 The following table is a rollforward of our allowance for credit losses related to the accounts receivable balances for the years ended December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Allowance for credit losses: Beginning balance $ 0.5 $ 0.3 Current period provision 5.4 2.5 Write-offs charged against allowances (6.0) (4.1) Recoveries collected 1.0 1.8 Ending balance $ 0.9 $ 0.5 The allowance for credit losses primarily relates to utility customer receivables, including unbilled amounts. Expected credit loss estimates are developed by disaggregating customers into those with similar credit risk characteristics and using historical credit loss experience. In addition, we also consider how current and future economic conditions are expected to impact collectability. Amounts are written off when reasonable collections efforts have been exhausted. Inventories Inventories are carried at average cost, net of reserves, and include materials and supplies used for utility operations. Regulatory Accounting As a regulated utility, AES Ohio applies the provisions of ASC 980 - Regulated Operations , which gives recognition to the ratemaking and accounting practices of the PUCO and the FERC. Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates. Regulatory assets can also represent performance incentives permitted by the regulator. Regulatory assets have been included as allowable costs for ratemaking purposes, as authorized by the PUCO or established regulatory practices. Regulatory liabilities generally represent obligations to make refunds or future rate reductions to customers for previous over collections or the deferral of revenue collected for costs that AES Ohio expects to incur in the future. The deferral of costs (as regulatory assets) is appropriate only when the future recovery of such costs is probable. In assessing probability, we consider such factors as specific orders from the PUCO or the FERC, regulatory precedent and the current regulatory environment. To the extent recovery of costs is no longer deemed probable, related regulatory assets would be required to be expensed in current period earnings. Our regulatory assets and liabilities have been created pursuant to a specific order of the PUCO or the FERC or established regulatory practices, such as other utilities under the jurisdiction of the PUCO or the FERC being granted recovery of similar costs. It is probable, but not certain, that these regulatory assets will be recoverable, subject to approval by the PUCO or the FERC. Regulatory assets and liabilities are classified as current or non-current based on the term in which recovery is expected. See Note 2. Regulatory Matters for more information. Property, Plant and Equipment New property, plant and equipment additions are stated at cost. For regulated transmission and distribution property, cost includes direct labor and material, allocable overhead expenses and AFUDC. AFUDC represents the cost of borrowed funds and equity used to finance regulated construction projects. Capitalization of AFUDC and interest ceases at either project completion or at the date specified by regulators. For substantially all depreciable property, when a unit of property is retired, the original cost of that property, less any salvage value, is charged to Accumulated depreciation and amortization , consistent with composite depreciation practices. Depreciation expense is calculated using the straight-line method, which allocates the cost of property over its estimated useful life. For AES Ohio’s transmission and distribution assets, straight-line depreciation is applied monthly on an average composite basis using group rates that approximated 2.6% in 2023, 2.8% in 2022 and 2.8% in 2021. Depreciation expense was $76.8 million, $75.6 million and $71.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. AFUDC In accordance with the Uniform System of Accounts prescribed by FERC, AES Ohio capitalizes an allowance for the net cost of funds (interest on borrowed funds and a reasonable rate of return on equity funds) used for construction purposes during the period of construction with a corresponding credit to income. AFUDC equity and AFUDC debt were as follows for the years ended December 31, 2023, 2022 and 2021: Years ended December 31, $ in millions 2023 2022 2021 AFUDC equity $ 5.0 $ 5.7 $ 2.1 AFUDC debt $ 6.5 $ 1.3 $ 1.6 Impairment of Long-lived Assets GAAP requires that we test long-lived assets for impairment when indicators of impairment exist. If an asset is deemed to be impaired, we are required to write down the asset to its fair value with a charge to current earnings. The net book value of our property, plant, and equipment was $2,195.9 million and $1,861.5 million as of December 31, 2023 and 2022, respectively. We do not believe any of these assets are currently impaired. In making this assessment, we consider such factors as: the overall condition and distribution capacity of the assets; the expected ability to recover additional expenditures in the assets; and the anticipated demand and relative pricing of retail electricity in our service territory. Intangible Assets Intangibles include software and renewable energy credits. Renewable energy credits are carried on a weighted average cost basis and amortized as they are used or retired. Finite-lived intangible assets include capitalized software amortized on a straight-line basis over their estimated useful lives. These capitalized software intangible assets have a seven year-weighted average amortization period. The following table presents information related to the Company's capitalized software balances, including the gross amount capitalized and related amortization: December 31, $ in millions 2023 2022 Capitalized software $ 142.2 $ 101.5 Accumulated amortization $ (30.8) $ (34.3) Years ended December 31, 2023 2022 2021 Amortization expense $ 3.9 $ 3.1 $ 3.0 Estimated future amortization Years ending December 31, 2024 $ 5.6 2025 5.6 2026 5.2 2027 4.6 2028 4.4 Total $ 25.4 Implementation Costs Related to Software as a Service AES Ohio has recorded prepayments for implementation costs related to software as a service in support of utility customer services of $14.8 million and $12.5 million as of December 31, 2023 and 2022, respectively, which are recorded within Other non-current assets on the accompanying Balance Sheets. Debt Issuance Costs Costs incurred in connection with the issuance of long-term debt are deferred and presented as a direct reduction from the face amount of that debt and amortized over the related financing period using the effective interest method. Debt issuance costs related to a line-of-credit or revolving credit facility are deferred and presented as an asset and amortized over the related financing period. Make-whole payments in connection with early debt retirements are classified as cash flows from financing activities. Contingencies AES Ohio accrues for loss contingencies when the amount of the loss is probable and estimable. We are subject to various environmental regulations and are involved in certain legal proceedings. If AES Ohio’s actual environmental and/or legal obligations are different from our estimates, the recognition of the actual amounts may have a material impact on our results of operations, financial condition and cash flows; although that has not been the case during the periods covered by this report. Accruals for loss contingencies were not material as of December 31, 2023 and 2022. See Note 9. Contractual Obligations, Commercial Commitments and Contingencies for additional information. Financial Instruments Our Master Trust investments in debt and equity financial instruments of publicly traded entities are classified as equity investments. These equity securities are carried at fair value and unrealized gains and losses on these securities are recorded in Other income . As these financial instruments are held to be used for the benefit of employees or former employees participating in employee benefit plans and are not used for general operating purposes, they are recorded within Other non-current assets on the accompanying Balance Sheets. See Note 4. Fair Value for more information. Financial Derivatives We have contracts involving the physical delivery of energy. These contracts qualify for the normal purchases and normal sales scope exception in ASC 815 - Derivatives and Hedging , thus we have elected to account for them as accrual contracts, which are not adjusted for changes in fair value. Accumulated other comprehensive loss The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2023, 2022 and 2021 are as follows: Details about AOCL Components Affected line in the Statements of Operations Years ended December 31, $ in millions 2023 2022 2021 Amortization of unfunded pension and other postretirement obligations (Note 7): Other expense $ 0.6 $ 3.6 $ 5.0 Income tax effect (0.2) (0.9) (1.1) Total reclassifications for the period, net of income taxes $ 0.4 $ 2.7 $ 3.9 The changes in the components of Accumulated other comprehensive loss during the years ended December 31, 2023 and 2022 are as follows: $ in millions Change in Accumulated other comprehensive loss Balance at January 1, 2022 $ (31.8) Other comprehensive income before reclassifications 2.3 Amounts reclassified from accumulated other comprehensive loss to earnings 2.7 Net current period other comprehensive income 5.0 Balance at December 31, 2022 (26.8) Other comprehensive loss before reclassifications (1.5) Amounts reclassified from accumulated other comprehensive loss to earnings 0.4 Net current period other comprehensive income (1.1) Balance at December 31, 2023 $ (27.9) Insurance and Claims Costs In addition to insurance obtained from third-party providers, MVIC, a wholly-owned captive subsidiary of DPL, provides insurance coverage solely to us and other DPL subsidiaries for workers’ compensation, general liability and property damage on an ongoing basis. AES Ohio is responsible for claims costs below certain coverage thresholds of MVIC and third-party insurers for the insurance coverage noted above. AES Ohio has estimated liabilities for medical, life, disability and other reserves for claims costs below certain coverage thresholds of third-party providers of approximately $3.5 million and $3.2 million at December 31, 2023 and 2022, respectively, within Accrued and other current liabilities and Other non-current liabilities on the accompanying Balance Sheets. The estimated liabilities for workers’ compensation, medical, life and disability costs at AES Ohio are actuarially determined using certain assumptions. There is uncertainty associated with these loss estimates, and actual results may differ from the estimates. Modification of these loss estimates based on experience and changed circumstances is reflected in the period in which the estimate is re-evaluated. Revenue Recognition Revenue is recognized from retail and wholesale electricity sales and electricity transmission and distribution delivery services. Revenue is recognized upon transfer of control of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. Energy sales to customers are based on the reading of their meters that occurs on a systematic basis throughout the month. We recognize the revenue on our Statements of Operations using an accrual method for retail and other energy sales that have not yet been billed, but where electricity has been consumed. This is termed “unbilled revenue” and is a widely recognized and accepted practice for utilities. At the end of each month, unbilled revenue is determined by the estimation of unbilled energy provided to customers since the date of the last meter reading, estimated line losses, the assignment of unbilled energy provided to customer classes and the average rate per customer class. For more information, see Note 11. Revenue . Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities AES Ohio collects certain excise taxes levied by state or local governments from its customers. AES Ohio’s excise taxes and certain other taxes are accounted for on a net basis and recorded as a reduction in revenue in the accompanying Statements of Operations. The amounts of such taxes were as follows: Years ended December 31, $ in millions 2023 2022 2021 Excise taxes collected $ 46.6 $ 49.2 $ 48.7 Repair and Maintenance Costs Costs associated with maintenance activities are recognized at the time the work is performed. These costs, which include labor, materials and supplies and outside services required to maintain equipment and facilities, are capitalized or expensed based on defined units of property. Pension and Postretirement Benefits We recognize in our Balance Sheets an asset or liability reflecting the funded status of pension and other postretirement plans with current-year changes from actuarial gains or losses related to our regulated operations, which would otherwise be recognized in AOCL, recorded as a regulatory asset as this can be recovered through future rates. Such changes that are not related to our regulated operations are recognized in AOCL. All plan assets are recorded at fair value. We follow the measurement date provisions of the accounting guidance, which require a year-end measurement date of plan assets and obligations for all defined benefit plans. We account for and disclose pension and postretirement benefits in accordance with the provisions of GAAP relating to the accounting for pension and other postretirement plans. These GAAP provisions require the use of assumptions, such as the discount rate for liabilities and long-term rate of return on assets, in determining the obligations, annual cost and funding requirements of the plans. Consistent with the requirements of ASC 715 - Compensation - Retirement Benefits , we apply a disaggregated discount rate approach for determining service cost and interest cost for our defined benefit pension plans and postretirement plans. See Note 7. Benefit Plans for more information. Income Taxes Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of the existing assets and liabilities and their respective income tax bases. We establish an allowance when it is more likely than not that all or a portion of a deferred tax asset will not be realized. Our tax positions are evaluated under a more likely than not recognition threshold and measurement analysis before they are recognized for financial statement reporting. Uncertain tax positions have been classified as noncurrent income tax liabilities unless expected to be paid within one year. Our policy for interest and penalties is to recognize interest and penalties as a component of the provision for income taxes in the Statements of Operations. Income taxes payable, which are includable in allowable costs for ratemaking purposes in future years, are recorded as regulatory assets or liabilities with a corresponding deferred tax liability or asset. Investment tax credits that reduced federal income taxes in the years they arose have been deferred and are being amortized to income over the useful lives of the properties in accordance with regulatory treatment. See Note 2. Regulatory Matters for more information. AES Ohio files U.S. federal income tax returns as part of the consolidated U.S. income tax return filed by AES. The consolidated tax liability is allocated to each subsidiary based on the separate return method as specified in our tax allocation agreement, and which provides a consistent, systematic and rational approach. See Note 6. Income Taxes for more information. Related Party Transactions In the normal course of business, AES Ohio enters into transactions with other subsidiaries of DPL or AES. See Note 10. Related Party Transactions for more information. New accounting pronouncements The following table provides a brief description of recent accounting pronouncements that could have an impact on our financial statements. Accounting pronouncements not listed below were assessed and determined to be either not applicable or did not have a material impact on our Financial Statements. ASU Number and Name Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Issued But Not Yet Effective 2023-06 Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative In U.S. Securities and Exchange Commission (SEC) Release No. 33-10532, Disclosure Update and Simplification, issued August 17, 2018, the SEC referred certain of its disclosure requirements that overlap with, but require incremental information to, generally accepted accounting principles (GAAP) to the FASB for potential incorporation into the Codification. The amendments in this Update are the result of the Board’s decision to incorporate into the Codification 14 of the 27 disclosures referred by the SEC. The amendments in this Update represent changes to clarify or improve disclosure and presentation requirements of a variety of Topics. Many of the amendments allow users to more easily compare entities subject to the SEC’s existing disclosures with those entities that were not previously subject to the SEC’s requirements. Also, the amendments align the requirements in the Codification with the SEC’s regulations. The effective date for each amendment will be the date on which the SEC's removal of that related disclosure becomes effective, with early adoption prohibited. The amendments in this Update should be applied prospectively We will provide the required disclosures on a prospective basis on the date each amendment becomes effective. We do not expect ASU 2023-06 will have any impact on our Financial Statements. 2023-07 Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures The amendments in this section are designed to improve the disclosures related to Segment reporting on an interim and annual basis. Public companies must disclose significant segment expenses and an amount for other segment items. This will also require that a company disclose its annual disclosures under Topic 280 in each interim period. Furthermore, companies will need to disclose the Chief Operating Decision Maker (CODM) and how the CODM assesses the performance of a segment. Lastly, public companies that have a single reportable segment must report the required disclosures under topic 280. The amendments in this Update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our Financial Statements. 2023-09 Income Taxes (Topic 740): Improvements to Income Tax Disclosures The amendments in this Update require that public business entities on an annual basis (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. Furthermore, companies are required to disclose a disaggregated amount of income taxes paid at a federal, state, and foreign level as well as a break down of income taxes paid in an jurisdiction that comprises 5% of a company's total income taxes paid. Lastly, this ASU requires that companies disclose income (loss) from continuing operations before income tax at a domestic and foreign level and that companies disclose income tax expense from continuing operations on a federal, state, and foreign level. The amendments in this Update are effective for fiscal years beginning after December 15, 2024 We are currently evaluating the impact of adopting the standard on our Financial Statements.

Regulatory Matters (Notes)

Regulatory Matters (Notes)	12 Months Ended
	Dec. 31, 2023
Schedule of Regulatory Assets and Liabilities [Text Block]	REGULATORY MATTERS AES Ohio ESPs and Smart Grid Comprehensive Settlement AES Ohio ESP - Ohio law requires utilities to file either an ESP or MRO plan to establish SSO rates. AES Ohio is currently operating pursuant to ESP 4, described in the paragraph below. From November 1, 2017 through December 18, 2019, AES Ohio operated pursuant to an approved ESP plan, which was initially approved on October 20, 2017 (ESP 3). On December 18, 2019, the PUCO approved AES Ohio's Notice of Withdrawal and reversion to its prior rate plan (ESP 1). Among other items, the PUCO Order approving the ESP 1 rate plan included reinstating the non-bypassable RSC Rider, which provided annual revenue of approximately $79.0 million. The OCC has appealed to the Ohio Supreme Court the PUCO’s decision approving the reversion to ESP 1 as well as argued for a refund of the RSC revenue dating back to August 2021. Oral argument regarding this appeal, which has been consolidated with the appeal regarding the Smart Grid Comprehensive Settlement described in the paragraph below, is expected but not yet scheduled. We are unable to predict the outcome of this appeal, but if this results in terms that are more adverse than AES Ohio's current ESP rate plan, it could have a material adverse effect on our results of operations, financial condition and cash flows. Smart Grid Comprehensive Settlement - On October 23, 2020, AES Ohio entered into a Stipulation and Recommendation (the Settlement) with the staff of the PUCO, various customers and organizations representing customers of AES Ohio and certain other parties with respect to, among other matters, AES Ohio's applications pending at the PUCO for (i) approval of AES Ohio's plan to modernize its distribution grid (Smart Grid Phase 1), (ii) findings that DP&L passed the SEET for 2018 and 2019, and (iii) findings that AES Ohio's ESP 1 satisfies the SEET and the more favorable in the aggregate (MFA) regulatory test. On June 16, 2021, the PUCO issued their opinion and order accepting the stipulation as filed. The OCC appealed the final PUCO order to the Ohio Supreme Court on December 6, 2021. Oral arguments regarding this appeal, which have been consolidated with the appeal regarding the reversion to ESP 1 described in the paragraph above, are expected but not yet scheduled. Smart Grid Phase 2 Plan - In February 2024, AES Ohio filed a Smart Grid Phase 2 with the PUCO proposing to invest approximately $683 million in capital projects over a 10-year period following the Smart Grid Phase 1, which ends June 2025. There are three principal components of AES Ohio’s Smart Grid Phase 2: 1) Distribution Operations, 2) Advanced Intelligence 3) Telecommunications and Cybersecurity. These initiatives will also allow AES Ohio to be ready to leverage and integrate Distributed Energy Resources into its grid. If approved, AES Ohio will implement a comprehensive grid modernization project that will deliver benefits to customers, society as a whole and to AES Ohio. A procedural schedule is expected that will provide for an Order by the second quarter of 2025 prior to the end of Smart Grid Phase 1. ESP 4 - On September 26, 2022, AES Ohio filed its latest ESP (ESP 4) with the PUCO. ESP 4 is a comprehensive plan to enhance and upgrade its network and improve service reliability, provide greater safeguards for price stability and continue investments in local economic development. On April 10, 2023, AES Ohio entered into a Stipulation and Recommendation with the PUCO Staff and seventeen parties (the “Settlement”) with respect to AES Ohio’s ESP 4 application, and, on August 9, 2023, the PUCO approved the Settlement without modification. The Settlement provides for a three-year ESP without a rate stability charge, and, in addition to other items, provides for the following: • A Distribution Investment Rider for the term of the ESP allowing for the timely recovery of distribution investments by AES Ohio based on a 9.999% return on equity, subject to revenue caps; • The recovery of approximately $66.0 million related to past expenditures by AES Ohio plus future carrying costs and the recovery of incremental vegetation management expenses up to certain annual limits during the term of ESP 4. During the third quarter of 2023, AES Ohio deferred $28.3 million of previously recognized purchased power costs and an additional $10.7 million of carrying costs related to this recovery; and • Funding of programs for assistance to low-income customers and for economic development. Additionally, with approval of this Settlement, the distribution rates that were approved by the PUCO on December 14, 2022, and are described in the paragraph below, became effective on September 1, 2023. Distribution Rate Case On November 30, 2020, AES Ohio filed a new distribution rate case application with the PUCO to increase AES Ohio’s base rates for electric distribution service to address, in part, increased costs of materials and labor and substantial investments to improve distribution structures. On December 14, 2022, the PUCO issued an order on the application. Among other matters, the order: • Establishes a revenue increase of $75.6 million for AES Ohio’s base rates for electric distribution service; and • Provides for a return on equity of 9.999% and a cost of long-term debt of 4.4% on a distribution rate base of $783.5 million and based on a capital structure of 53.87% equity and 46.13% long-term debt. These rates went into effect on September 1, 2023 with the approval of AES Ohio's ESP 4. FERC Transmission Rates On March 3, 2020, AES Ohio filed an application before the FERC seeking to change its existing stated transmission rates to formula transmission rates that would be updated each calendar year. An uncontested settlement was filed December 10, 2020 and approved April 15, 2021. Among other things, the settlement established new depreciation rates for AES Ohio’s transmission assets and an authorized return on equity of 9.85%, and started an amortization process to return excess deferred taxes created by the TCJA. Pursuant to the approved mechanisms and formula, transmission rates are adjusted each calendar year to reflect projected costs, adjusted to a true-up of actual revenue and costs incurred in the prior year. Regulatory Assets and Liabilities In accordance with ASC 980 - Regulated Operations ("ASC 980"), we have recognized total regulatory assets of $212.3 million and $169.0 million at December 31, 2023 and 2022, respectively, and total regulatory liabilities of $200.1 million and $239.1 million at December 31, 2023 and 2022, respectively. Regulatory assets and liabilities are classified as current or non-current based on the term in which recovery is expected. See Note 1. Overview and Summary of Significant Accounting Policies for accounting policies regarding Regulatory Assets and Liabilities. The following table presents DPL’s Regulatory assets and liabilities: Type of Recovery Amortization Through December 31, $ in millions 2023 2022 Regulatory assets, current: Undercollections to be collected through rate riders A/B 2024 $ 51.7 $ 38.7 Uncollectible expense being recovered in base rates B 2024 1.7 — Vegetation management being recovered in base rates B 2024 2.7 — Rate case expenses being recovered in base rates B 2024 0.5 0.5 Total regulatory assets, current 56.6 39.2 Regulatory assets, non-current: Pension benefits A/B Ongoing 62.6 64.2 Regulatory compliance costs A 2028 45.0 6.4 Energy efficiency D Undetermined 4.1 — Smart grid and AMI costs B/C Ongoing 3.2 2.3 Unamortized loss on reacquired debt B Ongoing 1.1 2.0 Deferred storm costs B Ongoing 2.2 8.7 Deferred rate case costs B 2028 1.5 1.9 Deferred vegetation management B 2028 19.9 21.9 CIS replacement D Undetermined 3.1 1.1 Transmission formula rate debits B 2025 6.7 — Decoupling deferral A 2028 — 13.8 Uncollectible deferral B 2028 6.3 7.5 Total regulatory assets, non-current 155.7 129.8 Total regulatory assets $ 212.3 $ 169.0 Regulatory liabilities, current: Overcollection of costs to be refunded through rate riders A/B 2024 $ 14.7 $ 27.6 Transmission formula rate credits B 2024 3.3 12.8 Total regulatory liabilities, current 18.0 40.4 Regulatory liabilities, non-current: Estimated costs of removal - regulated property Not Applicable 134.2 136.8 Deferred income taxes payable through rates Ongoing 42.6 45.2 TCJA regulatory liability B Ongoing 1.0 4.5 Transmission formula rate credits B 2024 — 5.4 PJM transmission enhancement settlement B 2025 1.7 3.5 Postretirement benefits B Ongoing 2.6 3.3 Total regulatory liabilities, non-current 182.1 198.7 Total regulatory liabilities $ 200.1 $ 239.1 A – Recovery of incurred costs plus rate of return. B – Recovery of incurred costs without a rate of return. C – Includes costs associated with Smart Grid Phase 2 development for which recovery is not yet determined but is considered probable of occurring in future rate proceedings. D – Recovery not determined, but recovery is probable of occurring in future rate proceedings. Current regulatory assets and liabilities Current regulatory assets primarily represent costs that are being recovered per specific rate orders; recovery for the remaining costs is probable, but not certain. Current regulatory assets include: (i) the Energy Efficiency Rider, (ii) the Economic Development Rider, (iii) the Storm Cost Rider, (iv) the Legacy Generation Rider, (v) the Infrastructure Investment Rider, (vi) the Regulatory Compliance Rider, (vii) the Proactive Reliability Optimization Rider, and (viii) the Distribution Investment Rider. Also included are the current portion of rate case expense, vegetation management, and uncollectible expense costs. Current regulatory liabilities include the overcollection of standard offer costs and certain transmission related costs, including the current portion of the PJM transmission enhancement settlement (discussed below), the transmission rate true-up, the Transmission Cost Recovery Rider overcollection and the TCJA regulatory liability. AES Ohio is earning a return on $9.3 million of the net undercollections / (overcollections) to be collected / (refunded) through rate riders including: (i) the Energy Efficiency Rider, (ii) the Economic Development Rider, and (iii) the Regulatory Compliance Rider, partially offset by the overcollection of standard offer costs and transmission costs. Pension benefits Pension benefits represent the qualifying ASC 715 costs of our regulated operations that for ratemaking purposes are deferred for future recovery. We recognize an asset for a plan’s overfunded status or a liability for a plan’s underfunded status, and recognize, as a component of OCI, the changes in the funded status of the plan that arise during the year that are not recognized as a component of net periodic benefit cost. This regulatory asset represents the regulated portion that would otherwise be charged as a loss to OCI. As per PUCO and FERC precedents, these costs are probable of future rate recovery. Regulatory compliance costs Regulatory compliance costs represent the long-term portion of the regulatory compliance costs which include the following costs: (i) Consumer Education Campaign, (ii) Retail Settlement System, (iii) Generation Separation, (iv) Bill Format Redesign, (v) Green Pricing Tariff, (vi) Supplier Consolidated Billing, (vii) Decoupling, (viii) a portion of previously deferred uncollectible costs, and (ix) unrecovered purchased power deferrals, and related carrying charges, approved in ESP 4. The balance of this regulatory asset earns a return with a maximum total to be accrued of $4.0 million. These costs are being recovered over a five-year period that began September 2023 through the Regulatory Compliance Rider approved in ESP 4. Energy Efficiency Rider Energy Efficiency Rider represents deferred expense and shared savings associated with energy efficiency programs that provide incentives and rebates for customers to improve the way they use electricity. The deferred expenses and shared savings were incurred prior to Ohio’s energy efficiency change in legislation and are therefore probable for recovery. The PUCO is currently conducting a prudency review, and a PUCO staff report was issued on February 2, 2024. Smart Grid and AMI costs Smart Grid and AMI costs represent costs incurred as a result of studying and developing distribution system upgrades and implementation of AMI related to Smart Grid Phase 1 and 2. AES Ohio developed Smart Grid Phase 1, which focuses on implementing new technology in the distribution business to upgrade customer meters, provide new customer programs related to energy efficiency and time-based rates, make certain infrastructure improvements, and upgrade substation and telecommunication equipment. Smart Grid Phase 1 costs are being recovered over a period of 4 years. AES Ohio has proposed Smart Grid Phase 2, which is pending before the PUCO. Unamortized loss on reacquired debt Unamortized loss on reacquired debt represents losses on long-term debt reacquired or redeemed in prior periods that have been deferred. These deferred losses are being amortized over the lives of the original issues in accordance with the rules of the FERC and the PUCO. Deferred storm costs Deferred storm costs represent the long-term portion of deferred costs for major storms which occurred during the second-half of 2023. AES Ohio files semi-annual petitions seeking recovery of storm costs. Recovery of these costs is probable, but not certain. Rate case expenses Rate case expenses represent costs associated with preparing distribution rate cases. AES Ohio was granted recovery of the 2020 rate case costs through base rates over a period of 5 years, without a rate of return. Vegetation management costs Vegetation management costs represent costs incurred from outside contractors for tree trimming and other vegetation management services. Historically deferred costs from 2018-2020 are being recovered in base rates with an amortization period of five years. In addition, ESP 4 approved a Proactive Reliability Optimization Rider which granted recovery of costs deferred starting from 2021 forward with an annual baseline of $20.0 million, subject to an annual maximum deferral of $7.5 million. These historical costs are also being recovered with an amortization period of five years. Annual spending less than the vegetation management baseline amount will result in a reduction to the regulatory asset or creation of a regulatory liability. CIS replacement costs Customer Information System (“CIS”) replacement costs represent operation and maintenance expenses associated with the implementation of a new CIS system. Deferral of these costs subject to an $8.8 million maximum deferral was approved in the Smart Grid Phase 1 Order, subject to demonstration that the functionality is available and a reasonableness prudence review. Recovery of these costs was requested and approved in Case No. 22-0900-EL-SSO to be included in the new Regulatory Compliance Rider, once the CIS is used and useful. Transmission formula rate debits/credits Transmission formula rate assets and liabilities represent the amounts due from/to customers as a result of the implementation of transmission formula rates, which are adjusted each year based on actual revenue and costs from a previous year, as described above under "FERC Transmission Rates". Decoupling deferral The decoupling deferral was approved for recovery via the Regulatory Compliance Rider in the ESP 4 Order and was reclassified to the Regulatory Compliance Rider asset in August 2023. The decoupling deferral represented the change in the revenue requirement based on a per customer methodology in the stipulation approved in the DRO and includes deferrals through December 18, 2019. Uncollectible deferral Uncollectible deferral represents deferred uncollectible expense associated with the nonpayment of electric service, less the revenue associated with the bypassable uncollectible portion of the standard offer rate. The 2023 distribution rate case order established that these costs would be recovered in base rates over a period of five years. Estimated costs of removal - regulated property Estimated costs of removal - regulated property reflect an estimate of amounts collected in customer rates for costs that are expected to be incurred in the future to remove existing transmission and distribution property from service when the property is retired. Deferred income taxes payable through rates Deferred income taxes payable through rates represent deferred income tax liabilities recognized from the normalization of flow-through items as the result of taxes previously charged to customers. A deferred income tax asset or liability is created from a difference in income recognition between tax laws and accounting methods. As a regulated utility, AES Ohio includes in ratemaking the impacts of current income taxes and changes in deferred income tax liabilities or assets. Accordingly, this liability reflects the estimated deferred taxes AES Ohio expects to return to customers in future periods. TCJA regulatory liability TCJA regulatory liability represents the long-term portion of both protected and unprotected excess Accumulated Deferred Income Taxes ("ADIT") for both transmission and distribution portions, grossed up to reflect the revenue requirement. As a part of the DRO, AES Ohio agreed that savings from the TCJA attributable to distribution facilities, including the excess ADIT and the regulatory liability, constitute amounts that will be returned to customers. As a result of the TCJA and subsequent DRO, AES Ohio entered into a stipulation to resolve all remaining TCJA items related to its distribution rates, including a proposal to return no less than $4.0 million per year for the first five years unless fully returned in the first five years via a tax savings cost rider for the distribution portion of the balance. On September 26, 2019, an order approved the stipulation in its entirety. PJM transmission enhancement settlement PJM transmission enhancement settlement liability represents the transmission enhancement settlement charges for which AES Ohio is due a refund per FERC Order EL05-121-009 issued on May 31, 2018. The Order states that customers are due a refund for part of these charges which will be received starting August 2018 through 2025. Refunds received will be returned to customers via the transmission cost rider. Postretirement benefits Postretirement benefits represent the qualifying ASC 715 gains related to our regulated operations that, for ratemaking purposes, are probable of being reflected in future rates. We recognize an asset for a plan’s overfunded status or a liability for a plan’s underfunded status, and recognize, as a component of OCI, the changes in the funded status of the plan that arise during the year that are not recognized as a component of net periodic benefit cost. This regulatory liability represents the regulated portion that would otherwise be reflected as a gain to OCI.
Subsidiaries [Member]
Schedule of Regulatory Assets and Liabilities [Text Block]	REGULATORY MATTERS AES Ohio ESPs and Smart Grid Comprehensive Settlement AES Ohio ESP - Ohio law requires utilities to file either an ESP or MRO plan to establish SSO rates. AES Ohio is currently operating pursuant to ESP 4, described in the paragraph below. From November 1, 2017 through December 18, 2019, AES Ohio operated pursuant to an approved ESP plan, which was initially approved on October 20, 2017 (ESP 3). On December 18, 2019, the PUCO approved AES Ohio's Notice of Withdrawal and reversion to its prior rate plan (ESP 1). Among other items, the PUCO Order approving the ESP 1 rate plan included reinstating the non-bypassable RSC Rider, which provided annual revenue of approximately $79.0 million. The OCC has appealed to the Ohio Supreme Court the PUCO’s decision approving the reversion to ESP 1 as well as argued for a refund of the RSC revenue dating back to August 2021. Oral argument regarding this appeal, which has been consolidated with the appeal regarding the Smart Grid Comprehensive Settlement described in the paragraph below, is expected but not yet scheduled. We are unable to predict the outcome of this appeal, but if this results in terms that are more adverse than AES Ohio's current ESP rate plan, it could have a material adverse effect on our results of operations, financial condition and cash flows. Smart Grid Comprehensive Settlement - On October 23, 2020, AES Ohio entered into a Stipulation and Recommendation (the Settlement) with the staff of the PUCO, various customers and organizations representing customers of AES Ohio and certain other parties with respect to, among other matters, AES Ohio's applications pending at the PUCO for (i) approval of AES Ohio's plan to modernize its distribution grid (Smart Grid Phase 1), (ii) findings that DP&L passed the SEET for 2018 and 2019, and (iii) findings that AES Ohio's ESP 1 satisfies the SEET and the more favorable in the aggregate (MFA) regulatory test. On June 16, 2021, the PUCO issued their opinion and order accepting the stipulation as filed. The OCC appealed the final PUCO order to the Ohio Supreme Court on December 6, 2021. Oral arguments regarding this appeal, which have been consolidated with the appeal regarding the reversion to ESP 1 described in the paragraph above, are expected but not yet scheduled. Smart Grid Phase 2 Plan - In February 2024, AES Ohio filed a Smart Grid Phase 2 with the PUCO proposing to invest approximately $683 million in capital projects over a 10-year period following the Smart Grid Phase 1, which ends June 2025. There are three principal components of AES Ohio’s Smart Grid Phase 2: 1) Distribution Operations, 2) Advanced Intelligence 3) Telecommunications and Cybersecurity. These initiatives will also allow AES Ohio to be ready to leverage and integrate Distributed Energy Resources into its grid. If approved, AES Ohio will implement a comprehensive grid modernization project that will deliver benefits to customers, society as a whole and to AES Ohio. A procedural schedule is expected that will provide for an Order by the second quarter of 2025 prior to the end of Smart Grid Phase 1. ESP 4 - On September 26, 2022, AES Ohio filed its latest ESP (ESP 4) with the PUCO. ESP 4 is a comprehensive plan to enhance and upgrade its network and improve service reliability, provide greater safeguards for price stability and continue investments in local economic development. On April 10, 2023, AES Ohio entered into a Stipulation and Recommendation with the PUCO Staff and seventeen parties (the “Settlement”) with respect to AES Ohio’s ESP 4 application, and, on August 9, 2023, the PUCO approved the Settlement without modification. The Settlement provides for a three-year ESP without a rate stability charge, and, in addition to other items, provides for the following: • A Distribution Investment Rider for the term of the ESP allowing for the timely recovery of distribution investments by AES Ohio based on a 9.999% return on equity, subject to revenue caps; • The recovery of approximately $66.0 million related to past expenditures by AES Ohio plus future carrying costs and the recovery of incremental vegetation management expenses up to certain annual limits during the term of ESP 4. During the third quarter of 2023, AES Ohio deferred $28.3 million of previously recognized purchased power costs and an additional $10.7 million of carrying costs related to this recovery; and • Funding of programs for assistance to low-income customers and for economic development. Additionally, with approval of this Settlement, the distribution rates that were approved by the PUCO on December 14, 2022, and are described in the paragraph below, became effective on September 1, 2023. Distribution Rate Case On November 30, 2020, AES Ohio filed a new distribution rate case application with the PUCO to increase AES Ohio’s base rates for electric distribution service to address, in part, increased costs of materials and labor and substantial investments to improve distribution structures. On December 14, 2022, the PUCO issued an order on the application. Among other matters, the order: • Establishes a revenue increase of $75.6 million for AES Ohio’s base rates for electric distribution service; and • Provides for a return on equity of 9.999% and a cost of long-term debt of 4.4% on a distribution rate base of $783.5 million and based on a capital structure of 53.87% equity and 46.13% long-term debt. These rates went into effect on September 1, 2023 with the approval of AES Ohio's ESP 4. FERC Transmission Rates On March 3, 2020, AES Ohio filed an application before the FERC seeking to change its existing stated transmission rates to formula transmission rates that would be updated each calendar year. An uncontested settlement was filed December 10, 2020 and approved April 15, 2021. Among other things, the settlement established new depreciation rates for AES Ohio’s transmission assets and an authorized return on equity of 9.85%, and started an amortization process to return excess deferred taxes created by the TCJA. Pursuant to the approved mechanisms and formula, transmission rates are adjusted each calendar year to reflect projected costs, adjusted to a true-up of actual revenue and costs incurred in the prior year. Regulatory Assets and Liabilities In accordance with ASC 980 - Regulated Operations ("ASC 980"), we have recognized total regulatory assets of $212.3 million and $169.0 million at December 31, 2023 and 2022, respectively, and total regulatory liabilities of $200.1 million and $239.1 million at December 31, 2023 and 2022, respectively. Regulatory assets and liabilities are classified as current or non-current based on the term in which recovery is expected. See Note 1. Overview and Summary of Significant Accounting Policies for accounting policies regarding Regulatory Assets and Liabilities. The following table presents AES Ohio’s Regulatory assets and liabilities: Type of Recovery Amortization Through December 31, $ in millions 2023 2022 Regulatory assets, current: Undercollections to be collected through rate riders A/B 2024 $ 51.7 $ 38.7 Uncollectible expense being recovered in base rates B 2024 1.7 — Vegetation management being recovered in base rates B 2024 2.7 — Rate case expenses being recovered in base rates B 2024 0.5 0.5 Total regulatory assets, current 56.6 39.2 Regulatory assets, non-current: Pension benefits A/B Ongoing 62.6 64.2 Regulatory compliance costs A 2028 45.0 6.4 Energy efficiency D Undetermined 4.1 — Smart grid and AMI costs B/C Ongoing 3.2 2.3 Unamortized loss on reacquired debt B Ongoing 1.1 2.0 Deferred storm costs B Ongoing 2.2 8.7 Deferred rate case costs B 2028 1.5 1.9 Deferred vegetation management B 2028 19.9 21.9 CIS replacement D Undetermined 3.1 1.1 Transmission formula rate debits B 2025 6.7 — Decoupling deferral A 2028 — 13.8 Uncollectible deferral B 2028 6.3 7.5 Total regulatory assets, non-current 155.7 129.8 Total regulatory assets $ 212.3 $ 169.0 Regulatory liabilities, current: Overcollection of costs to be refunded through rate riders A/B 2024 $ 14.7 $ 27.6 Transmission formula rate credits B 2024 3.3 12.8 Total regulatory liabilities, current 18.0 40.4 Regulatory liabilities, non-current: Estimated costs of removal - regulated property Not Applicable 134.2 136.8 Deferred income taxes payable through rates Ongoing 42.6 45.2 TCJA regulatory liability B Ongoing 1.0 4.5 Transmission formula rate credits B 2024 — 5.4 PJM transmission enhancement settlement B 2025 1.7 3.5 Postretirement benefits B Ongoing 2.6 3.3 Total regulatory liabilities, non-current 182.1 198.7 Total regulatory liabilities $ 200.1 $ 239.1 A – Recovery of incurred costs plus rate of return. B – Recovery of incurred costs without a rate of return. C – Includes costs associated with Smart Grid Phase 2 development for which recovery is not yet determined but is considered probable of occurring in future rate proceedings. D – Recovery not determined, but recovery is probable of occurring in future rate proceedings. Current regulatory assets and liabilities Current regulatory assets primarily represent costs that are being recovered per specific rate orders; recovery for the remaining costs is probable, but not certain. Current regulatory assets include: (i) the Energy Efficiency Rider, (ii) the Economic Development Rider, (iii) the Storm Cost Rider, (iv) the Legacy Generation Rider, (v) the Infrastructure Investment Rider, (vi) the Regulatory Compliance Rider, (vii) the Proactive Reliability Optimization Rider, and (viii) the Distribution Investment Rider. Also included are the current portion of rate case expense, vegetation management, and uncollectible expense costs. Current regulatory liabilities include the overcollection of standard offer costs and certain transmission related costs, including the current portion of the PJM transmission enhancement settlement (discussed below), the transmission rate true-up, the Transmission Cost Recovery Rider overcollection and the TCJA regulatory liability. AES Ohio is earning a return on $9.3 million of the net undercollections / (overcollections) to be collected / (refunded) through rate riders including: (i) the Energy Efficiency Rider, (ii) the Economic Development Rider, and (iii) the Regulatory Compliance Rider, partially offset by the overcollection of standard offer costs and transmission costs. Pension benefits Pension benefits represent the qualifying ASC 715 costs of our regulated operations that for ratemaking purposes are deferred for future recovery. We recognize an asset for a plan’s overfunded status or a liability for a plan’s underfunded status, and recognize, as a component of OCI, the changes in the funded status of the plan that arise during the year that are not recognized as a component of net periodic benefit cost. This regulatory asset represents the regulated portion that would otherwise be charged as a loss to OCI. As per PUCO and FERC precedents, these costs are probable of future rate recovery. Regulatory compliance costs Regulatory compliance costs represent the long-term portion of the regulatory compliance costs which include the following costs: (i) Consumer Education Campaign, (ii) Retail Settlement System, (iii) Generation Separation, (iv) Bill Format Redesign, (v) Green Pricing Tariff, (vi) Supplier Consolidated Billing, (vii) Decoupling, (viii) a portion of previously deferred uncollectible costs, and (ix) unrecovered purchased power deferrals, and related carrying charges, approved in ESP 4. The balance of this regulatory asset earns a return with a maximum total to be accrued of $4.0 million. These costs are being recovered over a five-year period that began September 2023 through the Regulatory Compliance Rider approved in ESP 4. Energy Efficiency Rider Energy Efficiency Rider represents deferred expense and shared savings associated with energy efficiency programs that provide incentives and rebates for customers to improve the way they use electricity. The deferred expenses and shared savings were incurred prior to Ohio’s energy efficiency change in legislation and are therefore probable for recovery. The PUCO is currently conducting a prudency review, and a PUCO staff report was issued on February 2, 2024. Smart Grid and AMI costs Smart Grid and AMI costs represent costs incurred as a result of studying and developing distribution system upgrades and implementation of AMI related to Smart Grid Phase 1 and 2. AES Ohio developed Smart Grid Phase 1, which focuses on implementing new technology in the distribution business to upgrade customer meters, provide new customer programs related to energy efficiency and time-based rates, make certain infrastructure improvements, and upgrade substation and telecommunication equipment. Smart Grid Phase 1 costs are being recovered over a period of 4 years. AES Ohio has proposed Smart Grid Phase 2, which is pending before the PUCO. Unamortized loss on reacquired debt Unamortized loss on reacquired debt represents losses on long-term debt reacquired or redeemed in prior periods that have been deferred. These deferred losses are being amortized over the lives of the original issues in accordance with the rules of the FERC and the PUCO. Deferred storm costs Deferred storm costs represent the long-term portion of deferred costs for major storms which occurred during the second-half of 2023. AES Ohio files semi-annual petitions seeking recovery of storm costs. Recovery of these costs is probable, but not certain. Rate case expenses Rate case expenses represent costs associated with preparing distribution rate cases. AES Ohio was granted recovery of the 2020 rate case costs through base rates over a period of 5 years, without a rate of return. Vegetation management costs Vegetation management costs represent costs incurred from outside contractors for tree trimming and other vegetation management services. Historically deferred costs from 2018-2020 are being recovered in base rates with an amortization period of five years. In addition, ESP 4 approved a Proactive Reliability Optimization Rider which granted recovery of costs deferred starting from 2021 forward with an annual baseline of $20.0 million, subject to an annual maximum deferral of $7.5 million. These historical costs are also being recovered with an amortization period of five years. Annual spending less than the vegetation management baseline amount will result in a reduction to the regulatory asset or creation of a regulatory liability. CIS replacement costs Customer Information System (“CIS”) replacement costs represent operation and maintenance expenses associated with the implementation of a new CIS system. Deferral of these costs subject to an $8.8 million maximum deferral was approved in the Smart Grid Phase 1 Order, subject to demonstration that the functionality is available and a reasonableness prudence review. Recovery of these costs was requested and approved in Case No. 22-0900-EL-SSO to be included in the new Regulatory Compliance Rider, once the CIS is used and useful. Transmission formula rate debits/credits Transmission formula rate assets and liabilities represent the amounts due from/to customers as a result of the implementation of transmission formula rates, which are adjusted each year based on actual revenue and costs from a previous year, as described above under "FERC Transmission Rates". Decoupling deferral The decoupling deferral was approved for recovery via the Regulatory Compliance Rider in the ESP 4 Order and was reclassified to the Regulatory Compliance Rider asset in August 2023. The decoupling deferral represented the change in the revenue requirement based on a per customer methodology in the stipulation approved in the DRO and includes deferrals through December 18, 2019. Uncollectible deferral Uncollectible deferral represents deferred uncollectible expense associated with the nonpayment of electric service, less the revenue associated with the bypassable uncollectible portion of the standard offer rate. The 2023 distribution rate case order established that these costs would be recovered in base rates over a period of five years. Estimated costs of removal - regulated property Estimated costs of removal - regulated property reflect an estimate of amounts collected in customer rates for costs that are expected to be incurred in the future to remove existing transmission and distribution property from service when the property is retired. Deferred income taxes payable through rates Deferred income taxes payable through rates represent deferred income tax liabilities recognized from the normalization of flow-through items as the result of taxes previously charged to customers. A deferred income tax asset or liability is created from a difference in income recognition between tax laws and accounting methods. As a regulated utility, AES Ohio includes in ratemaking the impacts of current income taxes and changes in deferred income tax liabilities or assets. Accordingly, this liability reflects the estimated deferred taxes AES Ohio expects to return to customers in future periods. TCJA regulatory liability TCJA regulatory liability represents the long-term portion of both protected and unprotected excess Accumulated Deferred Income Taxes ("ADIT") for both transmission and distribution portions, grossed up to reflect the revenue requirement. As a part of the DRO, AES Ohio agreed that savings from the TCJA attributable to distribution facilities, including the excess ADIT and the regulatory liability, constitute amounts that will be returned to customers. As a result of the TCJA and subsequent DRO, AES Ohio entered into a stipulation to resolve all remaining TCJA items related to its distribution rates, including a proposal to return no less than $4.0 million per year for the first five years unless fully returned in the first five years via a tax savings cost rider for the distribution portion of the balance. On September 26, 2019, an order approved the stipulation in its entirety. PJM transmission enhancement settlement PJM transmission enhancement settlement liability represents the transmission enhancement settlement charges for which AES Ohio is due a refund per FERC Order EL05-121-009 issued on May 31, 2018. The Order states that customers are due a refund for part of these charges which will be received starting August 2018 through 2025. Refunds received will be returned to customers via the transmission cost rider. Postretirement benefits Postretirement benefits represent the qualifying ASC 715 gains related to our regulated operations that, for ratemaking purposes, are probable of being reflected in future rates. We recognize an asset for a plan’s overfunded status or a liability for a plan’s underfunded status, and recognize, as a component of OCI, the changes in the funded status of the plan that arise during the year that are not recognized as a component of net periodic benefit cost. This regulatory liability represents the regulated portion that would otherwise be reflected as a gain to OCI.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT The following is a summary of DPL’s Property, plant and equipment with corresponding composite depreciation rates at December 31, 2023 and 2022: December 31, 2023 December 31, 2022 $ in millions Composite Rate Composite Rate Regulated: Transmission $ 505.3 2.5% $ 399.2 2.4% Distribution 1,860.9 3.5% 1,658.9 3.7% General 19.3 5.9% 20.7 5.2% Non-depreciable 99.5 N/A 79.4 N/A Total regulated 2,485.0 2,158.2 Unregulated: Other 31.3 4.1% 30.6 3.7% Non-depreciable 5.6 N/A 4.8 N/A Total unregulated 36.9 35.4 Total property, plant and equipment in service $ 2,521.9 3.2% $ 2,193.6 3.3%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	PROPERTY, PLANT AND EQUIPMENT The following is a summary of AES Ohio’s Property, plant and equipment with corresponding composite depreciation rates at December 31, 2023 and 2022: December 31, 2023 December 31, 2022 $ in millions Composite Rate Composite Rate Regulated: Transmission $ 648.0 2.0% $ 545.3 2.0% Distribution 2,283.4 2.9% 2,093.8 3.1% General 32.2 3.5% 34.2 4.0% Non-depreciable 99.6 N/A 79.4 N/A Total property, plant and equipment in service $ 3,063.2 2.6% $ 2,752.7 2.8%

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Entity Information [Line Items]
Fair Value Measurements	FAIR VALUE The fair value of our financial assets and liabilities approximate their reported carrying amounts. The estimated fair values of our assets and liabilities have been determined using available market information. Because these amounts are estimates and based on hypothetical transactions to sell assets or transfer liabilities, the use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. Fair Value Hierarchy and Valuation Techniques Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. These inputs are categorized using the market approach as follows for DPL: • Level 1 - unadjusted quoted prices for identical assets or liabilities in an active market. This includes inputs used for money market accounts that are considered cash equivalents, open-ended mutual funds and exchange-traded funds in the Master Trust. The fair value is determined by reference to quoted market prices and other relevant information generated by market transactions; • Level 2 - inputs from quoted prices in markets where trading occurs infrequently or quoted prices of instruments with similar attributes in active markets. This includes the common collective trust pension plan assets valued using the net asset value method. See Note 8. Benefit Plans for more information; and • Level 3 - unobservable inputs reflecting management’s own assumptions about the inputs used in pricing the asset or liability. These inputs are used for certain debt balances because the notes are not publicly traded. The fair value reflects management’s own assumptions about the inputs used in pricing the liability. Our long-term debt is fair valued for disclosure purposes only. The fair values of our financial instruments are based on published sources for pricing when possible. We rely on valuation models only when no other method is available to us. The fair value of our financial instruments represents estimates of possible value that may or may not be realized in the future. Valuations of assets and liabilities reflect the value of the instrument including the values associated with counterparty risk. We include our own credit risk and our counterparty’s credit risk in our calculation of fair value using global average default rates based on an annual study conducted by a large rating agency. We did not have any transfers of the fair values of our financial instruments among Level 1, Level 2 or Level 3 of the fair value hierarchy during the years ended December 31, 2023 and 2022. These financial instruments are not subject to master netting agreements or collateral requirements and, as such, are presented in the Consolidated Balance Sheets at their gross fair value. Financial Assets AES Ohio established a Master Trust to hold assets that could be used for the benefit of employees participating in employee benefit plans. These assets are not used for general operating purposes. These assets are primarily comprised of open-ended mutual funds, which are valued using the net asset value per unit. These investments are recorded at fair value within Other non-current assets on the Consolidated Balance Sheets and are classified as equity securities. Net unrealized gains / (losses) related to equity investments still held as of December 31, 2023 and 2022 are as follows: Years ended December 31, $ in millions 2023 2022 Net unrealized gains / (losses) (a) $ 0.5 $ (1.5) (a) These amounts are included in Other income, net in our Consolidated Statements of Operations. Recurring Fair Value Measurements The fair value of assets at December 31, 2023 and 2022 and the respective category within the fair value hierarchy for DPL was determined as follows: $ in millions Fair Value at December 31, 2023 Fair Value at December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Master trust assets Money market funds $ 0.6 $ — $ — $ 0.6 $ 0.5 $ — $ — $ 0.5 Mutual funds 7.2 — — 7.2 7.0 — — 7.0 Total assets $ 7.8 $ — $ — $ 7.8 $ 7.5 $ — $ — $ 7.5 Financial Instruments not Measured at Fair Value in the Consolidated Balance Sheets Our long-term debt is fair valued for disclosure purposes only and most of the fair values are determined using quoted market prices in inactive markets. These fair value inputs are considered Level 2 in the fair value hierarchy. As the Wright-Patterson Air Force Base note is not publicly traded, the fair value inputs are considered Level 3 in the fair value hierarchy as there are no observable inputs. Unrealized gains or losses are not recognized in the financial statements as long-term debt is presented at carrying value, net of unamortized premium or discount and unamortized deferred financing costs in the financial statements. The long-term debt amounts include the current portion payable in the next twelve months and have maturities that range from 2025 to 2061. Additional Level 3 disclosures are not presented since our long-term debt is not recorded at fair value. The following table presents the carrying amount, fair value, and fair value hierarchy of our financial liabilities that are not measured at fair value in the Consolidated Balance Sheets as of the periods indicated, but for which fair value is disclosed: Carrying Amount Fair Value at December 31, 2023 Carrying Amount Fair Value at December 31, 2022 $ in millions Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Long-term debt $ 1,837.6 $ — $ 1,706.2 $ 16.8 $ 1,723.0 $ 1,535.9 $ — $ 1,376.4 $ 17.0 $ 1,393.4
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Fair Value Measurements	FAIR VALUE The fair value of our financial assets and liabilities approximate their reported carrying amounts. The estimated fair values of our assets and liabilities have been determined using available market information. Because these amounts are estimates and based on hypothetical transactions to sell assets or transfer liabilities, the use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. Fair Value Hierarchy and Valuation Techniques Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. These inputs are categorized using the market approach as follows for AES Ohio: • Level 1 - unadjusted quoted prices for identical assets or liabilities in an active market. This includes inputs used for money market accounts that are considered cash equivalents, open-ended mutual funds and exchange-traded funds in the Master Trust. The fair value is determined by reference to quoted market prices and other relevant information generated by market transactions; • Level 2 - inputs from quoted prices in markets where trading occurs infrequently or quoted prices of instruments with similar attributes in active markets. This includes the common collective trust pension plan assets valued using the net asset value method. See Note 7. Benefit Plans for more information; and • Level 3 - unobservable inputs reflecting management’s own assumptions about the inputs used in pricing the asset or liability. These inputs are used for certain debt balances because the notes are not publicly traded. The fair value reflects management’s own assumptions about the inputs used in pricing the liability. Our long-term debt is fair valued for disclosure purposes only. The fair values of our financial instruments are based on published sources for pricing when possible. We rely on valuation models only when no other method is available to us. The fair value of our financial instruments represents estimates of possible value that may or may not be realized in the future. Valuations of assets and liabilities reflect the value of the instrument including the values associated with counterparty risk. We include our own credit risk and our counterparty’s credit risk in our calculation of fair value using global average default rates based on an annual study conducted by a large rating agency. We did not have any transfers of the fair values of our financial instruments among Level 1, Level 2 or Level 3 of the fair value hierarchy during the years ended December 31, 2023 and 2022 These financial instruments are not subject to master netting agreements or collateral requirements and, as such, are presented in the Balance Sheets at their gross fair value. Financial Assets AES Ohio established a Master Trust to hold assets that could be used for the benefit of employees participating in employee benefit plans. These assets are not used for general operating purposes. These assets are primarily comprised of open-ended mutual funds, which are valued using the net asset value per unit. These investments are recorded at fair value within Other non-current assets on the Balance Sheets and are classified as equity securities. Net unrealized gains / (losses) related to equity investments still held as of December 31, 2023 and 2022 are as follows: Years ended December 31, $ in millions 2023 2022 Net unrealized gains / (losses) (a) $ 0.5 $ (1.5) (a) These amounts are included in Other income / (expense), net in our Statements of Operations. Recurring Fair Value Measurements The fair value of assets at December 31, 2023 and 2022 and the respective category within the fair value hierarchy for AES Ohio was determined as follows: $ in millions Fair Value at December 31, 2023 Fair Value at December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Money market funds $ 0.6 $ — $ — $ 0.6 $ 0.5 $ — $ — $ 0.5 Mutual funds 7.2 — — 7.2 7.0 — — 7.0 Total assets $ 7.8 $ — $ — $ 7.8 $ 7.5 $ — $ — $ 7.5 Financial Instruments not Measured at Fair Value in the Balance Sheets Our long-term debt is fair valued for disclosure purposes only and most of the fair values are determined using quoted market prices in inactive markets. These fair value inputs are considered Level 2 in the fair value hierarchy. As the Wright-Patterson Air Force Base note is not publicly traded, the fair value inputs are considered Level 3 in the fair value hierarchy as there are no observable inputs. Unrealized gains or losses are not recognized in the financial statements as long-term debt is presented at carrying value, net of unamortized premium or discount and unamortized deferred financing costs in the financial statements. The long-term debt amounts include the current portion payable in the next twelve months and have maturities that range from 2027 to 2061. Additional Level 3 disclosures are not presented since our long-term debt is not recorded at fair value. The following table presents the carrying amount, fair value, and fair value hierarchy of our financial liabilities that are not measured at fair value in the Balance Sheets as of the periods indicated, but for which fair value is disclosed: Carrying Amount Fair Value at December 31, 2023 Carrying Amount Fair Value at December 31, 2022 $ in millions Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Long-term debt $ 1,012.5 $ — $ 909.9 $ 16.8 $ 926.7 $ 712.7 $ — $ 610.9 $ 17.0 $ 627.9

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2023
Derivative Instruments and Hedging Activities	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES DPL previously entered into interest rate derivative contracts to manage interest rate exposure related to anticipated borrowings of fixed-rate debt. The derivative instruments were used for risk management purposes and were designated as cash flow hedges if they qualified under ASC 815 for accounting purposes. These interest rate derivative contracts were settled in 2013 and we continue to amortize amounts out of AOCL into interest expense. The following tables provide information on gains recognized in AOCL for the cash flow hedges for the periods indicated: Years ended December 31, 2023 2022 2021 $ in millions (net of tax) Interest Rate Interest Rate Interest Rate Beginning accumulated derivative gain in AOCL $ 12.0 $ 12.8 $ 13.6 Net gains reclassified to earnings: Interest expense (0.8) (0.8) (0.8) Ending accumulated derivative gain in AOCL $ 11.2 $ 12.0 $ 12.8 Portion expected to be reclassified to earnings in the next twelve months $ (0.8)

Debt

Debt	12 Months Ended
	Dec. 31, 2023
Debt Instrument [Line Items]
Debt Disclosure	DEBT Long-term debt is as follows: $ in millions Interest Rate Maturity December 31, 2023 December 31, 2022 AES Ohio debt First Mortgage Bonds 3.95% 2049 $ 425.0 $ 425.0 First Mortgage Bonds 3.20% 2040 140.0 140.0 First Mortgage Bonds 5.70% 2033 107.5 — First Mortgage Bonds 5.19% 2033 100.0 — First Mortgage Bonds 5.49% 2028 92.5 — Tax-exempt First Mortgage Bonds (a) 4.25% 2027 100.0 100.0 Tax-exempt First Mortgage Bonds (b) 4.00% 2027 40.0 40.0 U.S. Government note 4.20% 2061 16.8 17.0 Unamortized deferred financing costs (7.1) (6.9) Unamortized debt discounts (2.2) (2.4) Total long-term debt at AES Ohio 1,012.5 712.7 Senior unsecured bonds 4.125% 2025 415.0 415.0 Senior unsecured bonds 4.35% 2029 400.0 400.0 Note to DPL Capital Trust II (c) 8.125% 2031 15.6 15.6 Unamortized deferred financing costs (4.9) (6.7) Unamortized debt discounts (0.6) (0.7) Total long-term debt 1,837.6 1,535.9 Less: current portion (0.2) (0.2) Long-term debt, net of current portion $ 1,837.4 $ 1,535.7 (a) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of November 1, 2040 but are subject to a mandatory put in June 2027. (b) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of January 1, 2034 but are subject to a mandatory put in June 2027. (c) Note payable to related party. See Note 11. Related Party Transactions for more information. Revolving Credit Agreements The DPL Credit Agreement was a committed line of credit secured by a pledge of common stock that DPL owns in AES Ohio and was used: (i) to finance capital expenditures; (ii) to refinance certain existing indebtedness, (iii) to support working capital; and (iv) for general corporate purposes. This agreement was retired on June 14, 2023. At December 31, 2022 the DPL Credit Agreement had outstanding borrowings of $35.0 million. AES Ohio entered into a second amendment and restatement of the AES Ohio Credit Agreement on December 22, 2022 with a syndication of bank lenders. The AES Ohio Credit Agreement is an unsecured committed line of credit to be used: (i) to finance capital expenditures; (ii) to refinance certain existing indebtedness, (iii) to support working capital; and (iv) for general corporate purposes. This agreement matures on December 22, 2027, and bears interest at variable rates as described in the agreement. It includes an uncommitted $100.0 million accordion feature to provide AES Ohio with an option to request an increase in the size of the facility, subject to approval by the lenders. The AES Ohio Credit Agreement also includes two one-year extension options, allowing AES Ohio to extend the maturity date subject to approval by the lenders. At December 31, 2023 and 2022, the AES Ohio Credit Agreement had outstanding borrowings of $15.0 million and $120.0 million, respectively. Debt Maturities At December 31, 2023, maturities of long-term debt are summarized as follows: Due during the years ending December 31, $ in millions 2024 $ 0.2 2025 415.2 2026 0.2 2027 140.2 2028 92.7 Thereafter 1,203.9 1,852.4 Unamortized debt discounts (2.8) Deferred financing costs, net (12.0) Total long-term debt $ 1,837.6 Significant Transactions On December 28, 2023, AES Ohio completed the offering of (i) $92.5 million in aggregate principal amount of First Mortgage Bonds, 5.49% Series due 2028 and (ii) $107.5 million aggregate principal amount of its First Mortgage Bonds, 5.70% Series due 2033 in a private placement. The proceeds from the offerings were used to repay existing indebtedness, including amounts outstanding under the AES Ohio Credit Agreement, and for general corporate purposes. On April 13, 2023, AES Ohio issued $100.0 million in aggregate principal amount of First Mortgage Bonds, 5.19% Series due 2033 in a private placement. The proceeds from the offering were used to repay amounts outstanding under the AES Ohio Credit Agreement and for general corporate purposes. On June 1, 2022, AES Ohio re-issued $140.0 million of tax-exempt OAQDA Collateralized Pollution Revenue Refunding Bonds that had been held in trust, Series 2015A&B. AES Ohio re-issued $140.0 million aggregate principal amount of first mortgage bonds to the OAQDA in two series: $100.0 million Series 2015A bonds at an interest rate of 4.25% and $40.0 million Series 2015B at an interest rate of 4.00% to secure the loan of proceeds from these bonds issued by the OAQDA. These bonds are subject to a mandatory put date of June 1, 2027. Debt Covenants and Restrictions The AES Ohio Credit Agreement and Fifty-Third, Fifty-Fourth and Fifty-Fifth Supplemental Indentures, pursuant to which the 3.20% Bonds due 2040, the 5.19% Bonds due 2033, the 5.49% Bonds due 2028 and the 5.70% Bonds due 2033 were issued, each contain one financial covenant, respectively. The covenant measures Total Debt to Total Capitalization and is calculated, at the end of each fiscal quarter, by dividing total debt by total capitalization. AES Ohio’s Total Debt to Total Capitalization ratio shall not be greater than 0.67 to 1.00. As of December 31, 2023, AES Ohio was in compliance with this financial covenant. AES Ohio does not have any meaningful restrictions in its debt financing documents prohibiting distributions to its parent, DPL. As of December 31, 2023, AES Ohio and DPL were in compliance with all debt covenants, including the financial covenants described above. Substantially all property, plant & equipment of AES Ohio is subject to the lien of the mortgage securing AES Ohio’s First and Refunding Mortgage.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt	DEBT Long-term debt is as follows: $ in millions Interest Rate Maturity December 31, 2023 December 31, 2022 First Mortgage Bonds 3.95% 2049 $ 425.0 $ 425.0 First Mortgage Bonds 3.20% 2040 140.0 140.0 First Mortgage Bonds 5.70% 2033 107.5 — First Mortgage Bonds 5.19% 2033 100.0 — First Mortgage Bonds 5.49% 2028 92.5 — Tax-exempt First Mortgage Bonds (a) 4.25% 2027 100.0 100.0 Tax-exempt First Mortgage Bonds (b) 4.00% 2027 40.0 40.0 U.S. Government note 4.20% 2061 16.8 17.0 Unamortized deferred financing costs (7.1) (6.9) Unamortized debt discounts (2.2) (2.4) Total long-term debt 1,012.5 712.7 Less: current portion (0.2) (0.2) Long-term debt, net of current portion $ 1,012.3 $ 712.5 (a) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of November 1, 2040 but are subject to a mandatory put in June 2027. (b) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of January 1, 2034 but are subject to a mandatory put in June 2027. Revolving Credit Agreement AES Ohio entered into a second amendment and restatement of the AES Ohio Credit Agreement on December 22, 2022 with a syndication of bank lenders. The AES Ohio Credit Agreement is an unsecured committed line of credit to be used: (i) to finance capital expenditures; (ii) to refinance certain existing indebtedness, (iii) to support working capital; and (iv) for general corporate purposes. This agreement matures on December 22, 2027, and bears interest at variable rates as described in the agreement. It includes an uncommitted $100.0 million accordion feature to provide AES Ohio with an option to request an increase in the size of the facility, subject to approval by the lenders. The AES Ohio Credit Agreement also includes two one-year extension options, allowing AES Ohio to extend the maturity date subject to approval by the lenders. At December 31, 2023 and 2022, the AES Ohio Credit Agreement had outstanding borrowings of $15.0 million and $120.0 million, respectively. Debt Maturities At December 31, 2023, maturities of long-term debt are summarized as follows: Due during the years ending December 31, $ in millions 2024 $ 0.2 2025 0.2 2026 0.2 2027 140.2 2028 92.7 Thereafter 788.3 1,021.8 Unamortized debt discounts (7.1) Deferred financing costs, net (2.2) Total long-term debt $ 1,012.5 Significant Transactions On December 28, 2023, AES Ohio completed the offering of (i) $92.5 million in aggregate principal amount of First Mortgage Bonds, 5.49% Series due 2028 and (ii) $107.5 million aggregate principal amount of its First Mortgage Bonds, 5.70% Series due 2033 in a private placement. The proceeds from the offerings were used to repay existing indebtedness, including amounts outstanding under the AES Ohio Credit Agreement, and for general corporate purposes. On April 13, 2023, AES Ohio issued $100.0 million in aggregate principal amount of First Mortgage Bonds, 5.19% Series due 2033 in a private placement. The proceeds from the offering were used to repay amounts outstanding under the AES Ohio Credit Agreement and for general corporate purposes. On June 1, 2022, AES Ohio re-issued $140.0 million of tax-exempt OAQDA Collateralized Pollution Revenue Refunding Bonds that had been held in trust, Series 2015A&B. AES Ohio re-issued $140.0 million aggregate principal amount of first mortgage bonds to the OAQDA in two series: $100.0 million Series 2015A bonds at an interest rate of 4.25% and $40.0 million Series 2015B at an interest rate of 4.00% to secure the loan of proceeds from these bonds issued by the OAQDA. These bonds are subject to a mandatory put date of June 1, 2027. Debt Covenants and Restrictions The AES Ohio Credit Agreement and Fifty-Third, Fifty-Fourth and Fifty-Fifth Supplemental Indentures, pursuant to which the 3.20% Bonds due 2040, the 5.19% Bonds due 2033, the 5.49% Bonds due 2028 and the 5.70% Bonds due 2033 were issued, each contain one financial covenant, respectively. The covenant measures Total Debt to Total Capitalization and is calculated, at the end of each fiscal quarter, by dividing total debt by total capitalization. AES Ohio’s Total Debt to Total Capitalization ratio shall not be greater than 0.67 to 1.00. As of December 31, 2023 AES Ohio was in compliance with this financial covenant. AES Ohio does not have any meaningful restrictions in its debt financing documents prohibiting distributions to its parent, DPL. As of December 31, 2023, AES Ohio was in compliance with all debt covenants, including the financial covenants described above. Substantially all property, plant & equipment of AES Ohio is subject to the lien of the mortgage securing AES Ohio’s First and Refunding Mortgage.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Taxes [Line Items]
Income Taxes	INCOME TAXES DPL’s components of income tax expense for both continuing and discontinued operations were as follows: Years ended December 31, $ in millions 2023 2022 2021 Components of tax expense / (benefit) Federal - current $ (20.0) $ (7.6) $ (5.5) State and local - current 0.4 — — Total current (19.6) (7.6) (5.5) Federal - deferred 24.5 (2.1) 4.4 State and local - deferred 1.7 0.1 0.4 Total deferred 26.2 (2.0) 4.8 Tax expense / (benefit) $ 6.6 $ (9.6) $ (0.7) Effective and Statutory Rate Reconciliation The following table summarizes a reconciliation of the U.S. statutory federal income tax rate to the effective tax rate, as a percentage of total income before taxes: Years ended December 31, 2023 2022 2021 Statutory Federal tax rate 21.0 % 21.0 % 21.0 % State taxes, net of Federal tax benefit 2.5 % (1.6) % 2.8 % AFUDC - equity (0.2) % 2.5 % 3.3 % Depreciation of flow-through differences (7.6) % 43.8 % (29.0) % Amortization of investment tax credits — % 0.1 % (0.6) % Other, net (0.1) % 1.3 % (0.8) % Effective tax rate 15.6 % 67.1 % (3.3) % Deferred Income Taxes Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and (b) operating loss carryforwards. These items are stated at the enacted tax rates that are expected to be in effect when taxes are actually paid or recovered. Investment tax credits related to utility property have been deferred and are being amortized over the estimated useful lives of the related property. The components of our deferred taxes are as follows: December 31, $ in millions 2023 2022 Net non-current assets / (liabilities) Depreciation / property basis $ (199.4) $ (185.5) Income taxes recoverable 9.5 9.2 Regulatory assets (39.3) (22.8) Investment tax credit — 0.1 Compensation and employee benefits (3.7) (2.8) Long-term debt 4.9 5.1 Other (a) 0.7 (2.3) Net non-current liabilities $ (227.3) $ (199.0) (a) The Other caption includes deferred tax assets of $35.9 million in 2023 and $36.6 million in 2022 related to state and local tax net operating loss carryforwards, with related valuation allowances of $35.7 million in 2023 and $36.6 million in 2022. These net operating loss carryforwards expire from 2024 to 2038. During the year ended December 31, 2023, DPL received a payment from AES of $21.0 million against its tax receivable balance as part of the $260.0 million in contributions received from AES. During the year ended December 31, 2021, DPL received a payment from AES of $17.5 million against its tax receivable balance as part of a $150.0 million contribution from AES. See Note 9. Shareholder's Equity / (Deficit) for more information. The following table presents the tax expense / (benefit) related to pensions, postemployment benefits, cash flow hedges and financial instruments that were credited to Accumulated other comprehensive loss: Years ended December 31, $ in millions 2023 2022 2021 Tax expense / (benefit) $ (0.6) $ 0.8 $ 2.2 Uncertain Tax Positions We apply the provisions of GAAP relating to the accounting for uncertainty in income taxes. The balance of unrecognized tax benefits did not change in 2023 and was $0.4 million at December 31, 2023 and 2022. The amount anticipated to result in a net decrease to unrecognized tax benefits within 12 months of December 31, 2023 is estimated to be $0.0 million. The following table presents the changes to our uncertain tax positions: $ in millions 2023 2022 2021 Unrecognized tax benefits at January 1 $ 0.4 $ 0.4 $ 1.4 Gross decreases - prior period tax positions — — (1.0) Unrecognized tax benefits at December 31 $ 0.4 $ 0.4 $ 0.4 Tax years subsequent to 2016 remain open to examination by taxing authorities. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, we believe we have appropriately accrued for our uncertain tax positions. However, audit outcomes and the timing of audit settlements and future events that would impact our previously recorded unrecognized tax benefits are subject to significant uncertainty. It is possible that the ultimate outcome of future examinations may exceed our provision for current unrecognized tax benefits. We recognize interest and penalties related to unrecognized tax benefits in Income tax benefit. The amounts accrued and the tax expense / (benefit) recorded were not material for each period presented. DPL is no longer subject to U.S. federal income tax examinations for tax years through 2016, but all subsequent periods are open. DPL is no longer subject to state income tax examinations for tax years through 2019 but all subsequent periods are open.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Income Taxes	INCOME TAXES AES Ohio’s components of income tax expense were as follows: Years ended December 31, $ in millions 2023 2022 2021 Components of tax expense / (benefit) Federal - current $ 4.1 $ (0.8) $ 1.1 State and local - current 0.4 — 0.1 Total current 4.5 (0.8) 1.2 Federal - deferred 7.3 (2.4) 4.1 State and local - deferred 1.7 0.1 0.4 Total deferred 9.0 (2.3) 4.5 Tax expense / (benefit) $ 13.5 $ (3.1) $ 5.7 Effective and Statutory Rate Reconciliation The following table summarizes a reconciliation of the U.S. statutory federal income tax rate to the effective tax rate, as a percentage of total income before taxes: Years ended December 31, 2023 2022 2021 Statutory Federal tax rate 21.0 % 21.0 % 21.0 % State taxes, net of Federal tax benefit 1.4 % 1.4 % 1.1 % AFUDC - Equity (0.1) % (2.2) % 1.3 % Amortization of investment tax credits — % (0.1) % (0.2) % Depreciation of flow-through differences (4.3) % (39.4) % (11.7) % Change in tax reserves — % — % (0.1) % Other - net — % (0.3) % (0.6) % Effective tax rate 18.0 % (19.6) % 10.8 % Deferred Income Taxes Deferred income taxes reflect the net tax effects of (a) temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and (b) operating loss carryforwards. These items are stated at the enacted tax rates that are expected to be in effect when taxes are actually paid or recovered. Investment tax credits related to utility property have been deferred and are being amortized over the estimated useful lives of the related property. The components of our deferred taxes are as follows: December 31, $ in millions 2023 2022 Net non-current assets / (liabilities) Depreciation / property basis $ (195.3) $ (181.3) Income taxes recoverable 9.5 9.2 Regulatory assets (39.3) (22.8) Investment tax credit — 0.1 Compensation and employee benefits (4.1) (3.1) Operating loss carryforwards 21.0 2.4 Other 2.1 0.6 Net non-current liabilities $ (206.1) $ (194.9) The following table presents the tax expense / (benefit) related to pensions, postemployment benefits, cash flow hedges and financial instruments that were credited to Accumulated other comprehensive loss . Years ended December 31, $ in millions 2023 2022 2021 Tax expense / (benefit) $ (0.3) $ 1.5 $ 2.9 Uncertain Tax Positions We apply the provisions of GAAP relating to the accounting for uncertainty in income taxes. The balance of unrecognized tax benefits did not change in 2023 and was $0.4 million at December 31, 2023 and December 31, 2022. The amount anticipated to result in a net decrease to unrecognized tax benefits within 12 months of December 31, 2023 is estimated to be $0.0 million. The following table presents the changes to our uncertain tax positions: $ in millions 2023 2022 2021 Unrecognized tax benefits at January 1 $ 0.4 $ 0.4 $ 1.4 Gross decreases - prior period tax positions — — (1.0) Unrecognized tax benefits at December 31 $ 0.4 $ 0.4 $ 0.4 Tax years subsequent to 2016 remain open to examination by taxing authorities. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, we believe we have appropriately accrued for our uncertain tax positions. However, audit outcomes and the timing of audit settlements and future events that would impact our previously recorded unrecognized tax benefits are subject to significant uncertainty. It is possible that the ultimate outcome of future examinations may exceed our provision for current unrecognized tax benefits. We recognize interest and penalties related to unrecognized tax benefits in Income tax benefit. The amounts accrued and the tax expense / (benefit) recorded were not material for each period presented. AES Ohio is no longer subject to U.S. federal income tax examinations for tax years through 2016, but all subsequent periods are open. AES Ohio is no longer subject to state income tax examinations for tax years through 2019, but all subsequent periods are open.

Benefit Plans

Benefit Plans	12 Months Ended
	Dec. 31, 2023
Benefit Plans	BENEFIT PLANS Postretirement Benefits Qualified employees who retired prior to 1987 and their dependents are eligible for health care and life insurance benefits until their death, while qualified employees who retired after 1987 are eligible for life insurance benefits and partially subsidized health care. The partially subsidized health care is at the election of the employee, who pays most of the cost, and is available only from their retirement until they are covered by Medicare. We have funded a portion of the union-eligible benefits using a Voluntary Employee Beneficiary Association Trust. These postretirement health care benefits and the related unfunded obligation of $7.2 million and $7.0 million at December 31, 2023 and 2022, respectively, were not material to the Consolidated Financial Statements in the periods covered by this report. Defined Contribution Plans The 401(k) Plans are qualified under Section 401 of the Internal Revenue Code. Participants may elect to contribute up to 85% of eligible compensation to their plan. Non-union participant contributions are matched 100% on the first 1% of eligible compensation and 50% on the next 5% of eligible compensation and they are fully vested in their employer contributions after 2 years of service. Union participant contributions are matched 150% but are capped at $2,750 for 2023 and they are fully vested in their employer contributions after 3 years of service. Certain non-union and union employees become eligible to participate in their respective plan upon date of hire. All participants are fully vested in their own contributions. We contributed $3.5 million, $3.3 million and $3.3 million for the years ended December 31, 2023, 2022 and 2021, respectively. AES Ohio matching contributions are paid bi-weekly, in arrears. The contributions by year may include the bi-weekly matching contribution that is paid in the following year in addition to employer matching true-up contributions. AES Ohio also contributes an annual bonus to the accounts of its union participants. This payment is typically made in January of the following year. Defined Benefit Plans AES Ohio sponsors a traditional defined benefit pension plan for most of the employees of DPL and its subsidiaries. For collective bargaining employees, the defined benefits are based on a specific dollar amount per year of service. For all other employees (management employees), the traditional defined benefit pension plan is based primarily on compensation and years of service. As of December 31, 2010, this traditional pension plan formula was closed to new management employees. A participant is 100% vested in all amounts credited to their account upon the completion of five vesting years, as defined in The Dayton Power and Light Company Retirement Income Plan, or the participant’s death or disability. If a participant’s employment is terminated, other than by death or disability, prior to such participant becoming 100% vested in his or her account, the account shall be forfeited as of the date of termination. Employees that transferred from AES Ohio to the Service Company maintain their previous eligibility to participate in the AES Ohio pension plan. Almost all management employees beginning employment on or after January 1, 2011 participate in a cash balance pension plan formula. Similar to the traditional pension plan for management employees, the cash balance benefits are based on compensation and years of service. A participant shall become 100% vested in all amounts credited to his or her account upon the completion of three vesting years, as defined in The Dayton Power and Light Company Retirement Income Plan, or the participant’s death or disability. If a participant’s employment is terminated, other than by death or disability, prior to such participant becoming 100% vested in his or her account, the account shall be forfeited as of the date of termination. Vested benefits in the cash balance plan are fully portable upon termination of employment. In addition, we have a Supplemental Executive Retirement Plan ("SERP") for certain retired key executives. The SERP has an immaterial unfunded liability related to agreements for retirement benefits of certain terminated and retired key executives. We recognize an asset for a plan’s overfunded status and a liability for a plan’s underfunded status and recognize, as a component of OCI, the changes in the funded status of the plan that arise during the year that are not recognized as a component of net periodic benefit cost. For the transmission and distribution areas of our electric business, these amounts are recorded as regulatory assets and liabilities which represent the regulated portion that would otherwise be charged or credited to AOCL. We have historically recorded these costs on an accrual basis, and this is how these costs have been historically recovered through customer rates. This factor, combined with the historical precedents from the PUCO and FERC, make these costs probable of future rate recovery. The following tables set forth the changes in the Pension Plans' obligations and assets recorded on the Consolidated Balance Sheets at December 31, 2023 and 2022. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $0.9 million, $1.7 million and $1.7 million of costs billed to the Service Company for the years ended December 31, 2023, 2022 and 2021, respectively. $ in millions Years ended December 31, Change in benefit obligation 2023 2022 Benefit obligation at January 1 $ 309.0 $ 416.2 Service cost 3.0 4.9 Interest cost 15.8 9.6 Plan amendments 1.4 — Actuarial loss / (gain) 9.6 (98.0) Benefits paid (40.2) (23.7) Benefit obligation at December 31 298.6 309.0 Change in plan assets Fair value of plan assets at January 1 274.4 363.5 Actual return / (loss) on plan assets 26.5 (73.1) Employer contributions 7.7 7.7 Benefits paid (40.2) (23.7) Fair value of plan assets at December 31 268.4 274.4 Unfunded status of plan $ (30.2) $ (34.6) December 31, Amounts recognized in the Consolidated Balance Sheets 2023 2022 Current liabilities $ (0.2) $ (0.2) Non-current liabilities (30.0) (34.4) Net liability at end of year $ (30.2) $ (34.6) Amounts recognized in Accumulated other comprehensive loss , Regulatory assets, non-current , pre-tax Components: Prior service cost $ 7.7 $ 7.3 Net actuarial loss 78.7 78.6 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 86.4 $ 85.9 Recorded in: Regulatory asset, non-current $ 60.7 $ 62.0 Accumulated other comprehensive loss 25.7 23.9 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 86.4 $ 85.9 The accumulated benefit obligation for our Pension Plans was $290.0 million and $301.3 million at December 31, 2023 and 2022, respectively. The net periodic benefit cost of the Pension Plans was: Years ended December 31, $ in millions 2023 2022 2021 Service cost $ 3.0 $ 4.9 $ 4.5 Interest cost 15.8 9.6 8.2 Expected return on assets (17.6) (15.8) (15.0) Amortization of unrecognized: Actuarial loss 0.6 5.5 9.0 Prior service cost 1.0 1.1 0.9 Net periodic benefit cost $ 2.8 $ 5.3 $ 7.6 Rates relevant to each year's expense calculations Discount rate 5.41 % 2.83 % 2.44 % Expected return on plan assets 5.40 % 4.60 % 4.55 % The components of net periodic benefit cost other than service cost are included in Total other expense, net in the Consolidated Statements of Operations. The following table presents other changes in Pension Plan assets and benefit obligations recognized in Accumulated other comprehensive loss , Regulatory assets, non-current and Regulatory liabilities, non-current : Years ended December 31, $ in millions 2023 2022 2021 Net actuarial loss / (gain) $ 0.7 $ (9.1) $ (21.7) Plan amendments 1.4 — 2.3 Reversal of amortization item: Net actuarial loss (0.6) (5.5) (9.0) Prior service cost (1.0) (1.1) (0.9) Total recognized in Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ 0.5 $ (15.7) $ (29.3) Total recognized in net periodic benefit cost and Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ 3.3 $ (10.4) $ (21.7) Significant Gains and Losses Related to Changes in the Benefit Obligation The actuarial loss of $9.6 million increased the benefit obligation for the year ended December 31, 2023 and an actuarial gain of $98.0 million decreased the benefit obligation for the year ended December 31, 2022. The actuarial loss in 2023 was primarily due to a decrease in the discount rate and the actuarial gain in 2022 was primarily due to an increase in the discount rate. Assumptions Our expected return on plan asset assumptions, used to determine benefit obligations, are based on historical long-term rates of return on investments, which use the widely accepted capital market principle that assets with higher volatility generate a greater return over the long run. Current market factors, such as inflation and interest rates, as well as asset diversification and portfolio rebalancing, are evaluated when long-term capital market assumptions are determined. Peer data and historical returns are reviewed to verify reasonableness and appropriateness. At December 31, 2023, we decreased the expected long-term rate of return on plan assets assumption to 5.15%. The rate of return represents our long-term assumptions based on our long-term portfolio mix. Also, at December 31, 2023, we decreased our assumed discount rate to 5.14% from 5.41% for pension expense to reflect current duration-based yield curve discount rates. A 1% increase / decrease in the rate of return assumption for pension would result in a corresponding decrease / increase in 2024 pension expense of approximately $2.9 million. A 0.25-percentage point increase / decrease in the discount rate for pension would result in a corresponding decrease / increase of approximately $0.3 million to 2024 pension expense. In determining the discount rate to use for valuing liabilities, we used a market yield curve on high-quality fixed income investments as of December 31, 2023. We project the expected benefit payments under the plan based on participant data and based on certain assumptions concerning mortality, retirement rates, termination rates, etc. The expected benefit payments for each year are then discounted back to the measurement date using the appropriate spot rate for each half-year from the yield curve, thereby obtaining a present value of all expected future benefit payments using the yield curve. Finally, an equivalent single discount rate is determined which produces a present value equal to the present value determined using the full yield curve. Consistent with the requirements of ASC 715, we apply a disaggregated discount rate approach for determining service cost and interest cost for our defined benefit pension plans and postretirement plans. In future periods, differences in the actual return on pension plan assets and assumed return, or changes in the discount rate, will affect the timing of contributions, if any, to the plans. The weighted average assumptions used to determine benefit obligations were: Benefit Obligation Assumptions Pension 2023 2022 2021 Discount rate for obligations 5.14% 5.41% 2.83% Rate of compensation increases 3.21% 3.21% 3.21% Pension Plan Assets Pension Plan assets are invested in multiple asset classes using a de-risking framework designed to manage the Pension Plan's funded status volatility and minimize future cash contributions. Investment strategies and asset allocations are intended to allocate additional assets to the fixed income asset class should the Pension Plan's funded status improve. Investment performance and asset allocation are measured and monitored on an ongoing basis. Pension Plan assets are managed in a balanced portfolio comprised of two major components: return seeking assets and liability hedging assets. The expected role of plan return seeking assets is to provide additional return with associated higher levels of risk, while the role of liability hedging assets is to correlate the interest rate of the fixed income investments with that of the Pension Plans' liabilities. Strategic asset allocation guidelines are determined by a Risk/Advisory Committee and approved by a Fiduciary Committee. These allocations consider the plan’s long-term objectives. The long-term target allocations for plan assets are 30% – 40% for return seeking assets and 60% – 70% for liability hedging assets. Return seeking assets include U.S. and international equity, while liability hedging assets include long-duration and high-yield bond funds and emerging market debt funds. The investment approach is to move the Pension Plans to a more de-risked position, if and when the overall funded status of the Pension Plans improve, by periodically rebalancing the allocation of the Pension Plans' investments in growth assets and liability hedging assets in accordance with the committee's glide path. This strategy requires the daily monitoring of the Pension Plans' ratio of assets to liabilities in order to determine whether approved trigger points have been met, requiring the rebalancing of the assets. All plan assets at December 31, 2023 are common collective trusts. With the exception of the cash and cash equivalents, the collective trusts are valued using the net asset value method and are categorized as Level 2 in the fair value hierarchy. The underlying investments are mutual funds, common stock. or debt securities, in alignment with the target asset allocation. The following table summarizes our target pension plan allocation: Long-Term Percentage of plan assets as of December 31, Asset category 2023 2022 Equity Securities 32% 32% 32% Debt Securities 68% 67% 67% Cash and Cash Equivalents —% 1% 1% The fair values of our Pension Plans' assets at December 31, 2023 by asset category are as follows: $ in millions Market Value at December 31, 2023 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 84.5 $ — $ 84.5 $ — Debt securities (b) 121.1 — 121.1 — Government debt securities (c) 61.0 — 61.0 — Total common collective trusts 266.6 — 266.6 — Cash and cash equivalents (d) 1.8 1.8 — — Total pension plan assets $ 268.4 $ 1.8 $ 266.6 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost. The fair values of our Pension Plans' assets at December 31, 2022 by asset category are as follows: $ in millions Market Value at December 31, 2022 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 88.5 $ — $ 88.5 $ — Debt securities (b) 125.7 — 125.7 — Government debt securities (c) 58.3 — 58.3 — Total common collective trusts 272.5 — 272.5 — Cash and cash equivalents (d) 1.9 1.9 — — Total pension plan assets $ 274.4 $ 1.9 $ 272.5 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost. Pension Funding We generally fund pension plan benefits as accrued in accordance with the minimum funding requirements of the Employee Retirement Income Security Act of 1974 ("ERISA") and, in addition, make voluntary contributions from time to time. We contributed $7.5 million, $7.5 million and $9.8 million to the pension plan in the years ended December 31, 2023, 2022 and 2021. We expect to make contributions of $0.2 million to our SERP in 2024 to cover benefit payments. We also expect to make contributions of $7.5 million to our pension plan during 2024. Funding for the Pension Plans is based upon actuarially determined contributions that consider the amount deductible for income tax purposes and the minimum contribution required under ERISA, as amended by the Pension Protection Act of 2006, as well as targeted funding levels necessary to meet certain thresholds. From an ERISA funding perspective, AES Ohio’s funded target liability percentage was estimated to be 100%. In addition, AES Ohio must also contribute the normal service cost earned by active participants during the plan year. The funding of normal cost is expected to be approximately $5.1 million in 2024, which includes $1.6 million for plan expenses. Each year thereafter, if the plan’s underfunding increases to more than the present value of the remaining annual installments, the excess is separately amortized over seven years. AES Ohio’s funding policy for the pension plans is to contribute annually no less than the minimum required by applicable law, and no more than the maximum amount that can be deducted for federal income tax purposes. Benefit payments, which reflect future service, are expected to be paid as follows: Estimated future benefit payments $ in millions due within the following years: Pension 2024 $ 22.4 2025 22.1 2026 22.1 2027 21.9 2028 21.8 2029 - 2033 106.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
Benefit Plans	BENEFIT PLANS Postretirement Benefits Qualified employees who retired prior to 1987 and their dependents are eligible for health care and life insurance benefits until their death, while qualified employees who retired after 1987 are eligible for life insurance benefits and partially subsidized health care. The partially subsidized health care is at the election of the employee, who pays most of the cost, and is available only from their retirement until they are covered by Medicare. We have funded a portion of the union-eligible benefits using a Voluntary Employee Beneficiary Association Trust. These postretirement health care benefits and the related unfunded obligation of $7.2 million and $7.0 million at December 31, 2023 and 2022, respectively, were not material to the Financial Statements in the periods covered by this report. Defined Contribution Plans The 401(k) Plans are qualified under Section 401 of the Internal Revenue Code. Participants may elect to contribute up to 85% of eligible compensation to their plan. Non-union participant contributions are matched 100% on the first 1% of eligible compensation and 50% on the next 5% of eligible compensation and they are fully vested in their employer contributions after 2 years of service. Union participant contributions are matched 150% but are capped at $2,750 for 2023 and they are fully vested in their employer contributions after 3 years of service. Certain non-union and union employees become eligible to participate in their respective plan upon date of hire. All participants are fully vested in their own contributions. We contributed $3.5 million, $3.3 million and $3.3 million for the years ended December 31, 2023, 2022 and 2021, respectively. AES Ohio matching contributions are paid bi-weekly, in arrears. The contributions by year may include the bi-weekly matching contribution that is paid in the following year in addition to employer matching true-up contributions. AES Ohio also contributes an annual bonus to the accounts of its union participants. This payment is typically made in January of the following year. Defined Benefit Plans AES Ohio sponsors a traditional defined benefit pension plan for most of the employees of DPL and its subsidiaries. For collective bargaining employees, the defined benefits are based on a specific dollar amount per year of service. For all other employees (management employees), the traditional defined benefit pension plan is based primarily on compensation and years of service. As of December 31, 2010, this traditional pension plan formula was closed to new management employees. A participant is 100% vested in all amounts credited to their account upon the completion of five vesting years, as defined in The Dayton Power and Light Company Retirement Income Plan, or the participant’s death or disability. If a participant’s employment is terminated, other than by death or disability, prior to such participant becoming 100% vested in his or her account, the account shall be forfeited as of the date of termination. Employees that transferred from AES Ohio to the Service Company maintain their previous eligibility to participate in the AES Ohio pension plan. Almost all management employees beginning employment on or after January 1, 2011 participate in a cash balance pension plan formula. Similar to the traditional pension plan for management employees, the cash balance benefits are based on compensation and years of service. A participant shall become 100% vested in all amounts credited to his or her account upon the completion of three vesting years, as defined in The Dayton Power and Light Company Retirement Income Plan, or the participant’s death or disability. If a participant’s employment is terminated, other than by death or disability, prior to such participant becoming 100% vested in his or her account, the account shall be forfeited as of the date of termination. Vested benefits in the cash balance plan are fully portable upon termination of employment. In addition, we have a Supplemental Executive Retirement Plan ("SERP") for certain retired key executives. The SERP has an immaterial unfunded liability related to agreements for retirement benefits of certain terminated and retired key executives. We recognize an asset for a plan’s overfunded status and a liability for a plan’s underfunded status and recognize, as a component of OCI, the changes in the funded status of the plan that arise during the year that are not recognized as a component of net periodic benefit cost. For the transmission and distribution areas of our electric business, these amounts are recorded as regulatory assets and liabilities which represent the regulated portion that would otherwise be charged or credited to AOCL. We have historically recorded these costs on an accrual basis, and this is how these costs have been historically recovered through customer rates. This factor, combined with the historical precedents from the PUCO and FERC, make these costs probable of future rate recovery. The following tables set forth the changes in the Pension Plans' obligations and assets recorded on the Balance Sheets at December 31, 2023 and 2022. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $0.9 million, $1.7 million and $1.7 million of costs billed to the Service Company for the years ended December 31, 2023, 2022 and 2021, respectively, or $0.2 million, $0.9 million and $1.9 million of costs billed to AES Ohio Generation for the years ended December 31, 2023, 2022 and 2021, respectively. $ in millions Years ended December 31, Change in benefit obligation 2023 2022 Benefit obligation at January 1 $ 309.0 $ 416.2 Service cost 3.0 4.9 Interest cost 15.8 9.6 Plan amendments 1.4 — Actuarial loss / (gain) 9.6 (98.0) Benefits paid (40.2) (23.7) Benefit obligation at December 31 298.6 309.0 Change in plan assets Fair value of plan assets at January 1 274.4 363.5 Actual return / (loss) on plan assets 26.5 (73.1) Employer contributions 7.7 7.7 Benefits paid (40.2) (23.7) Fair value of plan assets at December 31 268.4 274.4 Unfunded status of plan $ (30.2) $ (34.6) December 31, Amounts recognized in the Balance Sheets 2023 2022 Current liabilities $ (0.2) $ (0.2) Non-current liabilities (30.0) (34.4) Net liability at end of year $ (30.2) $ (34.6) Amounts recognized in Accumulated other comprehensive loss , Regulatory assets, non-current , pre-tax Components: Prior service cost $ 7.6 $ 7.3 Net actuarial loss 102.3 102.7 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 109.9 $ 110.0 Recorded in: Regulatory assets, non-current $ 60.7 $ 62.0 Accumulated other comprehensive loss 49.2 48.0 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 109.9 $ 110.0 The accumulated benefit obligation for our Pension Plans was $290.0 million and $301.3 million at December 31, 2023 and 2022, respectively. The net periodic benefit cost of the Pension Plans was: Years ended December 31, $ in millions 2023 2022 2021 Service cost $ 3.0 $ 4.9 $ 4.5 Interest cost 15.8 9.6 8.2 Expected return on assets (17.6) (15.8) (15.0) Amortization of unrecognized: Actuarial loss 1.1 7.7 11.4 Prior service cost 1.1 1.2 1.1 Net periodic benefit cost $ 3.4 $ 7.6 $ 10.2 Rates relevant to each year's expense calculations Discount rate 5.41 % 2.83 % 2.44 % Expected return on plan assets 5.40 % 4.60 % 4.55 % The components of net periodic benefit cost other than service cost are included in Total other expense, net in the Statements of Operations. The following table presents other changes in plan assets and benefit obligations recognized in Accumulated other comprehensive loss , Regulatory assets, non-current and Regulatory liabilities, non-current: Years ended December 31, $ in millions 2023 2022 2021 Net actuarial loss / (gain) $ 0.7 $ (9.1) $ (21.7) Plan amendments 1.4 — 2.3 Reversal of amortization item: Net actuarial loss (1.1) (7.7) (11.4) Prior service cost (1.1) (1.2) (1.1) Total recognized in Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ (0.1) $ (18.0) $ (31.9) Total recognized in net periodic benefit cost and Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ 3.3 $ (10.4) $ (21.7) Significant Gains and Losses Related to Changes in the Benefit Obligation The actuarial loss of $9.6 million increased the benefit obligation for the year ended December 31, 2023 and an actuarial gain of $98.0 million decreased the benefit obligation for the year ended December 31, 2022. The actuarial loss in 2023 was primarily due to a decrease in the discount rate and the actuarial gain in 2022 was primarily due to an increase in the discount rate. Assumptions Our expected return on plan asset assumptions, used to determine benefit obligations, are based on historical long-term rates of return on investments, which use the widely accepted capital market principle that assets with higher volatility generate a greater return over the long run. Current market factors, such as inflation and interest rates, as well as asset diversification and portfolio rebalancing, are evaluated when long-term capital market assumptions are determined. Peer data and historical returns are reviewed to verify reasonableness and appropriateness. At December 31, 2023, we decreased the expected long-term rate of return on plan assets assumption to 5.15%. The rate of return represents our long-term assumptions based on our long-term portfolio mix. Also, at December 31, 2023, we decreased our assumed discount rate to 5.14% from 5.41% for pension expense to reflect current duration-based yield curve discount rates. A 1% increase / decrease in the rate of return assumption for pension would result in a corresponding decrease / increase in 2024 pension expense of approximately $2.9 million. A 0.25-percentage point increase / decrease in the discount rate for pension would result in a corresponding decrease / increase of approximately $0.3 million to 2024 pension expense. In determining the discount rate to use for valuing liabilities, we used a market yield curve on high-quality fixed income investments as of December 31, 2023. We project the expected benefit payments under the plan based on participant data and based on certain assumptions concerning mortality, retirement rates, termination rates, etc. The expected benefit payments for each year are then discounted back to the measurement date using the appropriate spot rate for each half-year from the yield curve, thereby obtaining a present value of all expected future benefit payments using the yield curve. Finally, an equivalent single discount rate is determined which produces a present value equal to the present value determined using the full yield curve. Consistent with the requirements of ASC 715, we apply a disaggregated discount rate approach for determining service cost and interest cost for our defined benefit pension plans and postretirement plans. In future periods, differences in the actual return on pension plan assets and assumed return, or changes in the discount rate, will affect the timing of contributions, if any, to the plans. The weighted average assumptions used to determine benefit obligations were: Benefit Obligation Assumptions Pension 2023 2022 2021 Discount rate for obligations 5.14% 5.41% 2.83% Rate of compensation increases 3.21% 3.21% 3.21% Pension Plan Assets Pension Plan assets are invested in multiple asset classes using a de-risking framework designed to manage the Pension Plan's funded status volatility and minimize future cash contributions. Investment strategies and asset allocations are intended to allocate additional assets to the fixed income asset class should the Pension Plan's funded status improve. Investment performance and asset allocation are measured and monitored on an ongoing basis. Pension Plan assets are managed in a balanced portfolio comprised of two major components: return seeking assets and liability hedging assets. The expected role of plan return seeking assets is to provide additional return with associated higher levels of risk, while the role of liability hedging assets is to correlate the interest rate of the fixed income investments with that of the Pension Plans' liabilities. Strategic asset allocation guidelines are determined by a Risk/Advisory Committee and approved by a Fiduciary Committee. These allocations consider the plan’s long-term objectives. The long-term target allocations for plan assets are 30% – 40% for return seeking assets and 60% – 70% for liability hedging assets. Return seeking assets include U.S. and international equity, while liability hedging assets include long-duration and high-yield bond funds and emerging market debt funds. The investment approach is to move the Pension Plans to a more de-risked position, if and when the overall funded status of the Pension Plans improve, by periodically rebalancing the allocation of the Pension Plans' investments in growth assets and liability hedging assets in accordance with the committee's glide path. This strategy requires the daily monitoring of the Pension Plans' ratio of assets to liabilities in order to determine whether approved trigger points have been met, requiring the rebalancing of the assets. All plan assets at December 31, 2023 are common collective trusts. With the exception of the cash and cash equivalents, the collective trusts are valued using the net asset value method and are categorized as Level 2 in the fair value hierarchy. The underlying investments are mutual funds, common stock. or debt securities, in alignment with the target asset allocation. The following table summarizes our target pension plan allocation: Long-Term Percentage of plan assets as of December 31, Asset category 2023 2022 Equity Securities 32% 32% 32% Debt Securities 68% 67% 67% Cash and Cash Equivalents —% 1% 1% The fair values of our Pension Plans' assets at December 31, 2023 by asset category are as follows: $ in millions Market Value at December 31, 2023 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 84.5 $ — $ 84.5 $ — Debt securities (b) 121.1 — 121.1 — Government debt securities (c) 61.0 — 61.0 — Total common collective trusts 266.6 — 266.6 — Cash and cash equivalents (d) 1.8 1.8 — — Total pension plan assets $ 268.4 $ 1.8 $ 266.6 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost. The fair values of our pension plan assets at December 31, 2022 by asset category are as follows: $ in millions Market Value at December 31, 2022 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 88.5 $ — $ 88.5 $ — Debt securities (b) 125.7 — 125.7 — Government debt securities (c) 58.3 — 58.3 — Total common collective trusts 272.5 — 272.5 — Cash and cash equivalents (d) 1.9 1.9 — — Total pension plan assets $ 274.4 $ 1.9 $ 272.5 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost. Pension Funding We generally fund pension plan benefits as accrued in accordance with the minimum funding requirements of the Employee Retirement Income Security Act of 1974 ("ERISA") and, in addition, make voluntary contributions from time to time. We contributed $7.5 million, $7.5 million and $9.8 million to the pension plan in the years ended December 31, 2023, 2022 and 2021. We expect to make contributions of $0.2 million to our SERP in 2024 to cover benefit payments. We also expect to make contributions of $7.5 million to our pension plan during 2024. Funding for the Pension Plans is based upon actuarially determined contributions that consider the amount deductible for income tax purposes and the minimum contribution required under ERISA, as amended by the Pension Protection Act of 2006, as well as targeted funding levels necessary to meet certain thresholds. From an ERISA funding perspective, AES Ohio’s funded target liability percentage was estimated to be 100%. In addition, AES Ohio must also contribute the normal service cost earned by active participants during the plan year. The funding of normal cost is expected to be approximately $5.1 million in 2024, which includes $1.6 million for plan expenses. Each year thereafter, if the plan’s underfunding increases to more than the present value of the remaining annual installments, the excess is separately amortized over seven years. AES Ohio’s funding policy for the pension plans is to contribute annually no less than the minimum required by applicable law, and no more than the maximum amount that can be deducted for federal income tax purposes. Benefit payments, which reflect future service, are expected to be paid as follows: Estimated future benefit payments $ in millions due within the following years: Pension 2024 $ 22.4 2025 22.1 2026 22.1 2027 21.9 2028 21.8 2029 - 2033 106.7

Equity

Equity	12 Months Ended
	Dec. 31, 2023
Entity Information [Line Items]
Stockholders' Equity Note Disclosure [Text Block]	SHAREHOLDER'S EQUITY / (DEFICIT) Common Stock Effective on the Merger date, DPL's Amended Articles of Incorporation provided for 1,500 authorized common shares, of which one share is outstanding at December 31, 2023. AES Ohio has 50,000,000 authorized common shares, of which 41,172,173 are outstanding at December 31, 2023. All common shares are held by AES Ohio’s parent, DPL. Capital Contributions from AES DPL received $260.0 million and $150.0 million in cash contributions from AES during the years ended December 31, 2023 and 2021, respectively; which DPL then used to make equity contributions of $260.0 million and $150.0 million, respectively, to AES Ohio. The cash contributions at DPL represented equity contributions of $239.0 million in 2023 and $132.5 million in 2021; and payments of $21.0 million and $17.5 million against its tax receivable in 2023 and 2021, respectively. The proceeds from the equity contributions at AES Ohio have enabled AES Ohio to seek to improve its infrastructure and modernize its grid while maintaining liquidity. DPL did not receive any contributions from AES in 2022. Dividend Restrictions DPL’s Amended Articles of Incorporation (the Articles) contain provisions which state that DPL may not make a distribution to its shareholder or make a loan to any of its affiliates (other than its subsidiaries), unless: (a) there exists no Event of Default (as defined in the Articles) and no such Event of Default would result from the making of the distribution or loan; and either (b)(i) at the time of, and/or as a result of, the distribution or loan, DPL’s leverage ratio does not exceed 0.67 to 1.00 and DPL’s interest coverage ratio is not less than 2.50 to 1.00 or, (b)(ii) if such ratios are not within the parameters, DPL’s senior long-term debt rating from one of the three major credit rating agencies is at least investment grade. Further, the restrictions on the payment of distributions to a shareholder and the making of loans to its affiliates (other than subsidiaries) cease to be in effect if the three major credit rating agencies confirm that a lowering of DPL’s senior long-term debt rating below investment grade by the credit rating agencies would not occur without these restrictions. As described above, DPL’s Amended Articles of Incorporation contains restrictions on DPL’s ability to make dividends, distributions and affiliate loans (other than to its subsidiaries), including restrictions on making such dividends, distributions and loans if certain financial ratios exceed specified levels and DPL’s senior long-term debt rating from a rating agency is below investment grade. As of December 31, 2023, DPL did not meet these requirements and was prohibited under its Articles of Incorporation from making a distribution to its shareholder or making a loan to any of its affiliates (other than its subsidiaries).
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Stockholders' Equity Note Disclosure [Text Block]	SHAREHOLDER'S EQUITY Common Stock AES Ohio has 50,000,000 authorized common shares, of which 41,172,173 are outstanding at December 31, 2023. All common shares are held by AES Ohio’s parent, DPL. Capital Contributions and Returns of Capital AES Ohio received $260.0 million and $150.0 million in capital contributions from DPL in the years ended December 31, 2023 and 2021, respectively. The proceeds from these equity contributions allow AES Ohio to seek to improve its infrastructure and modernize its grid while maintaining liquidity. AES Ohio did not receive any contributions from DPL in 2022. During the years ended December 31, 2023 and 2022, AES Ohio declared and paid distributions totaling $83.0 million and $64.0 million, respectively. During the year ended December 31, 2021, AES Ohio declared distributions of $42.0 million and paid distributions of $52.0 million.

Contractual Obligations, Commer

Contractual Obligations, Commercial Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Contractual Obligations, Commercial Commitments and Contingencies	CONTRACTUAL OBLIGATIONS, COMMERCIAL COMMITMENTS AND CONTINGENCIES Contractual Obligations and Commercial Commitments We enter into various contractual obligations and other commercial commitments that may affect the liquidity of our operations. At December 31, 2023, these include: Payments due in: $ in millions Total Less than 2 - 3 4 - 5 More than Electricity purchase commitments $ 569.3 $ 365.8 $ 203.5 $ — $ — Purchase orders and other contractual obligations $ 421.1 $ 318.3 $ 83.4 $ 19.4 $ — Electricity purchase commitments AES Ohio enters into long-term contracts for the purchase of electricity through the SSO competitive bid auctions. In general, these contracts are subject to variable quantities and are terminable only in limited circumstances. Purchase orders and other contractual obligations At December 31, 2023, DPL had various other contractual obligations including contracts to purchase goods and services with various terms and expiration dates. Due to uncertainty regarding the timing and payment of future obligations to the Service Company, and DPL's ability to terminate such obligations upon 90 days' notice, we have excluded such amounts in the contractual obligations table above. Contingencies Legal Matters In the normal course of business, we are subject to various lawsuits, actions, proceedings, claims and other matters asserted under laws and regulations. We believe the amounts provided in our Consolidated Financial Statements, as prescribed by GAAP, are adequate considering the probable and estimable contingencies. However, there can be no assurances that the actual amounts required to satisfy alleged liabilities from various legal proceedings, claims, tax examinations and other matters, including the matters discussed below, and to comply with applicable laws and regulations, will not exceed the amounts reflected in our Consolidated Financial Statements. As such, costs, if any, that may be incurred in excess of those amounts provided as of December 31, 2023, cannot be reasonably determined. Environmental Matters We are subject to various federal, state, regional and local environmental protection and health and safety laws and regulations governing, among other things, the generation, storage, handling, use, disposal and transportation of regulated materials, including ash; the use and discharge of water used in generation boilers and for cooling purposes; the emission and discharge of hazardous and other materials, including GHGs, into the environment; climate change; and the health and safety of our employees. These laws and regulations often require a lengthy and complex process of obtaining and renewing permits and other governmental authorizations from federal, state and local agencies. Violation of these laws, regulations or permits can result in substantial fines, other sanctions, permit revocation and/or facility shutdowns. We cannot assure that we have been or will be at all times in full compliance with such laws, regulations and permits. Where no accrued liability has been recognized, it is reasonably possible that some matters could be decided unfavorably to the us and could require us to pay damages or make expenditures in amounts that could be material but could not be estimated as of December 31, 2023. We have taken steps to limit our exposure to environmental claims that could be raised with respect to our previously-owned and operated coal-fired generation units, but we cannot predict whether any such claims will be raised and, if they are, the extent to which they may have a material adverse effect on our results of operations, financial condition and cash flows. Accruals for legal loss and environmental contingencies were not material as of December 31, 2023 and December 31, 2022. Equity Ownership Interest AES Ohio has a 4.9% equity ownership interest in OVEC, which is recorded using the cost method of accounting under GAAP. AES Ohio, along with several non-affiliated energy companies party to an OVEC arrangement, receive and pay for OVEC capacity and energy and are responsible for OVEC debt obligations and other fixed costs in proportion to their power participation ratios under the arrangement, which, for AES Ohio, is the same as its equity ownership interest. As of December 31, 2023, AES Ohio could be responsible for the repayment of 4.9%, or $52.5 million, of $1.1 billion OVEC debt obligations if they came due, comprised of both fixed and variable rate securities with maturities from 2026 to 2040. OVEC could also seek additional contributions from AES Ohio to avoid a default in the event that other OVEC members defaulted on their respective OVEC obligations.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Contractual Obligations, Commercial Commitments and Contingencies	CONTRACTUAL OBLIGATIONS, COMMERCIAL COMMITMENTS AND CONTINGENCIES Contractual Obligations and Commercial Commitments We enter into various contractual obligations and other commercial commitments that may affect the liquidity of our operations. At December 31, 2023, these include: Payments due in: $ in millions Total Less than 2 - 3 4 - 5 More than Electricity purchase commitments $ 569.3 $ 365.8 $ 203.5 $ — $ — Purchase orders and other contractual obligations $ 419.4 $ 316.6 $ 83.4 $ 19.4 $ — Electricity purchase commitments AES Ohio enters into long-term contracts for the purchase of electricity through the SSO competitive bid auctions. In general, these contracts are subject to variable quantities and are terminable only in limited circumstances. Purchase orders and other contractual obligations At December 31, 2023, AES Ohio had various other contractual obligations including contracts to purchase goods and services with various terms and expiration dates. Due to uncertainty regarding the timing and payment of future obligations to the Service Company, and AES Ohio's ability to terminate such obligations upon 90 days' notice, we have excluded such amounts in the contractual obligations table above. Contingencies Legal Matters In the normal course of business, we are subject to various lawsuits, actions, proceedings, claims and other matters asserted under laws and regulations. We believe the amounts provided in our Financial Statements, as prescribed by GAAP, are adequate considering the probable and estimable contingencies. However, there can be no assurances that the actual amounts required to satisfy alleged liabilities from various legal proceedings, claims, tax examinations and other matters, including the matters discussed below, and to comply with applicable laws and regulations, will not exceed the amounts reflected in our Financial Statements. As such, costs, if any, that may be incurred in excess of those amounts provided as of December 31, 2023, cannot be reasonably determined. Environmental Matters We are subject to various federal, state, regional and local environmental protection and health and safety laws and regulations governing, among other things, the generation, storage, handling, use, disposal and transportation of regulated materials, including ash; the use and discharge of water used in generation boilers and for cooling purposes; the emission and discharge of hazardous and other materials, including GHGs, into the environment; climate change; and the health and safety of our employees. These laws and regulations often require a lengthy and complex process of obtaining and renewing permits and other governmental authorizations from federal, state and local agencies. Violation of these laws, regulations or permits can result in substantial fines, other sanctions, permit revocation and/or facility shutdowns. We cannot assure that we have been or will be at all times in full compliance with such laws, regulations and permits. Where no accrued liability has been recognized, it is reasonably possible that some matters could be decided unfavorably to the us and could require us to pay damages or make expenditures in amounts that could be material but could not be estimated as of December 31, 2023. We have taken steps to limit our exposure to environmental claims that could be raised with respect to our previously-owned and operated coal-fired generation units, but we cannot predict whether any such claims will be raised and, if they are, the extent to which they may have a material adverse effect on our results of operations, financial condition and cash flows. Accruals for legal loss and environmental contingencies were not material as of December 31, 2023 and December 31, 2022. Equity Ownership Interest AES Ohio has a 4.9% equity ownership interest in OVEC, which is recorded using the cost method of accounting under GAAP. AES Ohio, along with several non-affiliated energy companies party to an OVEC arrangement, receive and pay for OVEC capacity and energy and are responsible for OVEC debt obligations and other fixed costs in proportion to their power participation ratios under the arrangement, which, for AES Ohio, is the same as its equity ownership interest. As of December 31, 2023, AES Ohio could be responsible for the repayment of 4.9%, or $52.5 million, of $1.1 billion OVEC debt obligations if they came due, comprised of both fixed and variable rate securities with maturities from 2026 to 2040. OVEC could also seek additional contributions from AES Ohio to avoid a default in the event that other OVEC members defaulted on their respective OVEC obligations.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Entity Information [Line Items]
Related Party Transactions	RELATED PARTY TRANSACTIONS Service Company The Service Company allocates the costs for services provided based on cost drivers designed to result in fair and equitable allocations. This includes ensuring that the regulated utilities served, including AES Ohio, are not subsidizing costs incurred for the benefit of other businesses. Benefit Plans DPL participates in an agreement with Health and Welfare Benefit Plans LLC, an affiliate of AES, to participate in a group benefits program, including but not limited to, health, dental, vision and life benefits. Health and Welfare Benefit Plans LLC administers the financial aspects of the group insurance program, receives all premium payments from the participating affiliates, and makes all vendor payments. Long-term Compensation Plan During 2023, 2022 and 2021, some of DPL’s non-union employees received benefits under the AES Long-term Compensation Plan, a deferred compensation program. This type of plan is a common employee retention tool used in our industry. Benefits under this plan are granted in the form of performance units payable in cash and AES restricted stock units. Restricted stock units vest ratably over a three-year period. The performance units payable in cash vest at the end of the three-year performance period and are subject to certain AES performance criteria. Total deferred compensation expense for the years ended December 31, 2023, 2022 and 2021 was not material and is included in Operation and maintenance on DPL’s Consolidated Statements of Operations. The value of these benefits is being recognized over the 36-month vesting period and a portion is recorded as miscellaneous deferred credits with the remainder included in Other paid-in capital on DPL’s Consolidated Balance Sheets in accordance with ASC 718 - Compensation - Stock Compensation . The following table provides a summary of our related party transactions: Years ended December 31, $ in millions 2023 2022 2021 The following transactions are included in Operation and Maintenance on the Consolidated Statements of Operations: Net charges from the Service Company $ 48.3 $ 39.9 $ 34.9 Services provided by AES and other AES affiliates $ 16.8 $ 16.5 $ 15.5 Services provided by other related parties $ 1.7 $ 2.5 $ 1.6 Balances with related parties (included in Accounts Receivable, net and A ccounts Payable ): At December 31, 2023 At December 31, 2022 Net payable to the Service Company $ (3.9) $ (9.8) Net receivable from AES and other AES affiliates $ — $ 0.3 DPL Capital Trust II DPL has a wholly-owned business trust, DPL Capital Trust II (the Trust), formed for the purpose of issuing trust capital securities to third-party investors. Effective in 2003, DPL deconsolidated the Trust upon adoption of the accounting standards related to variable interest entities and currently treats the Trust as a nonconsolidated subsidiary. The Trust holds mandatorily redeemable trust capital securities. The investment in the Trust, which amounted to $0.1 million and $0.2 million at December 31, 2023 and 2022, respectively, is included in Other non-current assets on the Consolidated Balance Sheets. DPL also has a note payable to the Trust amounting to $15.6 million and $15.6 million at December 31, 2023 and 2022, respectively, that was established upon the Trust’s deconsolidation in 2003. This note payable is included in Long-term debt on the Consolidated Balance Sheets. In addition to the obligations under the note payable mentioned above, DPL also agreed to a security obligation which represents a full and unconditional guarantee of payments to the capital security holders of the Trust. Income Taxes AES files federal and state income tax returns which consolidate DPL and its subsidiaries. Under a tax sharing agreement with AES, DPL is responsible for the income taxes associated with its own taxable income and records the provision for income taxes using a separate return method.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Related Party Transactions	RELATED PARTY TRANSACTIONS Service Company The Service Company allocates the costs for services provided based on cost drivers designed to result in fair and equitable allocations. This includes ensuring that the regulated utilities served, including AES Ohio, are not subsidizing costs incurred for the benefit of other businesses. Benefit Plans DPL participates in an agreement with Health and Welfare Benefit Plans LLC, an affiliate of AES, to participate in a group benefits program, including but not limited to, health, dental, vision and life benefits. Health and Welfare Benefit Plans LLC administers the financial aspects of the group insurance program, receives all premium payments from the participating affiliates, and makes all vendor payments. Long-term Compensation Plan During 2023, 2022 and 2021, many of AES Ohio’s non-union employees received benefits under the AES Long-term Compensation Plan, a deferred compensation program. This type of plan is a common employee retention tool used in our industry. Benefits under this plan are granted in the form of performance units payable in cash and AES restricted stock units. Restricted stock units vest ratably over a three-year period. The performance units payable in cash vest at the end of the three-year performance period and are subject to certain AES performance criteria. Total deferred compensation expense for the years ended December 31, 2023, 2022 and 2021 was not material and is included in Operation and maintenance on AES Ohio’s Statements of Operations. The value of these benefits is being recognized over the 36-month vesting period and a portion is recorded as miscellaneous deferred credits with the remainder included in Other paid-in capital on AES Ohio’s Balance Sheets in accordance with ASC 718 - Compensation - Stock Compensation . The following table provides a summary of our related party transactions: Years ended December 31, $ in millions 2023 2022 2021 The following transactions are included in Operation and Maintenance on the Statements of Operations: Net charges from the Service Company $ 47.5 $ 39.2 $ 33.9 Services provided by AES and other AES affiliates $ 32.2 $ 28.1 $ 21.9 Services provided by other related parties $ 1.7 $ 2.5 $ 1.6 Balances with related parties (include in Accounts Receivable, net and Accounts Payable ): At December 31, 2023 At December 31, 2022 Net payable to the Service Company $ (3.9) $ (9.8) Net receivable from AES and other AES affiliates $ 2.4 $ 1.2 Income Taxes AES files federal and state income tax returns which consolidate DPL and its subsidiaries, including AES Ohio. Under a tax sharing agreement with DPL, AES Ohio is responsible for the income taxes associated with its own taxable income and records the provision for income taxes using a separate return method. Under this agreement, AES Ohio had a net receivable balance of $24.4 million and $29.6 million at December 31, 2023 and 2022, respectively, which are recorded in Taxes receivable on the accompanying Balance Sheets. During 2023, 2022 and 2021, AES Ohio made no payments to DPL for its share of income taxes.

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2023
Segment Reporting Information [Line Items]
Business Segments	BUSINESS SEGMENTS DPL manages its business through one reportable operating segment, the Utility segment. The primary segment performance measure is income / (loss) from continuing operations before income tax as management has concluded that this measure best reflects the underlying business performance of DPL and is the most relevant measure considered in DPL’s internal evaluation of the financial performance of its segment. The Utility segment is comprised of AES Ohio, a public electric transmission and distribution utility, with all other nonutility business activities aggregated separately. See Note 1. Overview and Summary of Significant Accounting Policies for further information on AES Ohio. The “Other” nonutility category primarily includes interest expense, cash and other immaterial balances. The accounting policies of the identified segment are consistent with those policies and procedures described in the summary of significant accounting policies. The following tables present financial information for DPL’s reportable business segment: $ in millions Utility Other Adjustments and Eliminations DPL Consolidated Year ended December 31, 2023 Revenue from external customers $ 851.3 $ 9.7 $ — $ 861.0 Intersegment revenue 0.7 4.4 (5.1) — Total revenue $ 852.0 $ 14.1 $ (5.1) $ 861.0 Depreciation and amortization $ 80.7 $ 1.4 $ — $ 82.1 Interest expense $ 25.8 $ 37.8 $ — $ 63.6 Income / (loss) from continuing operations before income tax $ 74.9 $ (32.6) $ — $ 42.3 Cash capital expenditures $ 384.3 $ 3.6 $ — $ 387.9 $ in millions Utility Other Adjustments and Eliminations DPL Consolidated Year ended December 31, 2022 Revenue from external customer $ 859.3 $ 9.7 $ — $ 869.0 Intersegment revenue 0.8 3.6 (4.4) — Total revenue $ 860.1 $ 13.3 $ (4.4) $ 869.0 Depreciation and amortization $ 78.7 $ 1.3 $ — $ 80.0 Interest expense $ 28.8 $ 39.0 $ — $ 67.8 Income / (loss) from continuing operations before income tax $ 15.8 $ (30.1) $ — $ (14.3) Cash capital expenditures $ 283.7 $ 3.6 $ — $ 287.3 $ in millions Utility Other Adjustments and Eliminations DPL Consolidated Year ended December 31, 2021 Revenue from external customer $ 663.0 $ 9.7 $ — $ 672.7 Intersegment revenue 0.7 3.5 (4.2) — Total revenue $ 663.7 $ 13.2 $ (4.2) $ 672.7 Depreciation and amortization $ 74.6 $ 1.5 $ — $ 76.1 Interest expense $ 24.2 $ 38.7 $ — $ 62.9 Income / (loss) from continuing operations before income tax $ 52.8 $ (30.4) $ — $ 22.4 Cash capital expenditures $ 189.3 $ 2.0 $ — $ 191.3 Total Assets December 31, 2023 December 31, 2022 December 31, 2021 Utility $ 2,871.0 $ 2,405.9 $ 2,162.6 All Other (a) 35.2 16.5 9.2 DPL Consolidated $ 2,906.2 $ 2,422.4 $ 2,171.8 (a) "All Other" includes Eliminations for all periods presented.

Revenue (Notes)

Revenue (Notes)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Text Block]	REVENUE Revenue is primarily earned from retail and wholesale electricity sales and electricity transmission and distribution delivery services. Revenue is recognized upon transfer of control of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. Revenue is recorded net of any taxes assessed on and collected from customers, which are remitted to the governmental authorities. Retail revenue AES Ohio energy sales to utility customers are based on the reading of meters at the customer's location that occurs on a systematic basis throughout the month. AES Ohio sells electricity directly to end-users, such as homes and businesses, and bills customers directly. Performance obligations for retail revenue are satisfied over time as energy is delivered and the same method is used to measure progress, and thus the performance obligation meets the criteria to be considered a series. This includes both the promise to transfer energy and other distribution and/or transmission services. In exchange for the exclusive right to sell or distribute electricity in our service area, AES Ohio is subject to rate regulation by federal and state regulators. This regulation sets the framework for the prices (“tariffs”) that AES Ohio is allowed to charge customers for electricity. Since tariffs are approved by the regulator, the price that AES Ohio has the right to bill corresponds directly with the value to the customer of AES Ohio's performance completed in each period. Therefore, revenue under these contracts is recognized using an output method measured by the MWhs delivered each month at the approved tariff. In cases where a customer chooses to receive generation services from a CRES provider, the price for generation services is negotiated between the customer and the CRES provider, and AES Ohio only serves as a billing agent if requested by the CRES provider. As such, AES Ohio recognizes the consolidated billing arrangement with the CRES provider on a net basis, thereby recording no revenue for the generation component. Retail revenue from these customers would only be related to transmission and distribution charges. Wholesale revenue AES Ohio's share of the power produced at OVEC is sold to PJM and this revenue is classified as Wholesale revenue. In PJM, the promise to sell energy as wholesale revenue is separately identifiable from participation in the capacity market and the two products can be transacted independently of one another. Therefore, wholesale revenue is a separate contract with a single performance obligation. Revenue is recorded based on the quantities (MWh) delivered in each hour during each month at the spot price, making the contract effectively “month-to-month”. RTO ancillary revenue Compensation for use of AES Ohio’s transmission assets and compensation for various ancillary services are classified as RTO ancillary revenue. As AES Ohio owns and operates transmission lines in southwest Ohio within PJM, demand charges collected from network customers by PJM are then allocated to the appropriate transmission owners (i.e. AES Ohio) and recognized as transmission revenue. Transmission revenue has a single performance obligation, as transmission services represent a distinct service. Additionally, as the performance obligation is satisfied over time and the same method is used to measure progress, the performance obligation meets the criteria to be considered a series. The price that AES Ohio, as the transmission operator, has the right to bill (received as a credit from PJM) corresponds directly with the value to the customer of performance completed in each period, as the price paid is the allocation of the tariff rate (as approved by the regulator) charged to network participants. Capacity revenue AES Ohio records its share of OVEC capacity revenue as Capacity revenue. The capacity price is set through a competitive auction process established by PJM. Depending on the availability and performance of the OVEC units, there may be additional performance bonuses or penalties, which would be recognized only if it becomes probable that such bonus or penalties will be incurred. RTO capacity revenue has a single performance obligation, as capacity is a distinct good. Additionally, as the performance obligation is satisfied over time and the same method is used to measure progress, the performance obligation meets the criteria to be considered a series. The capacity price is set through a competitive auction process established by PJM. DPL's revenue from contracts with customers was $861.6 million, $861.4 million and $667.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. The following table presents our revenue from contracts with customers and other revenue by segment for the years ended December 31, 2023, 2022 and 2021: $ in millions Utility Other Adjustments and Eliminations Total Year ended December 31, 2023 Retail revenue Retail revenue from contracts with customers Residential revenue $ 478.9 $ — $ — $ 478.9 Commercial revenue 162.1 — — 162.1 Industrial revenue 66.6 — — 66.6 Governmental revenue 24.3 — — 24.3 Other (a) 13.0 — — 13.0 Total retail revenue from contracts with customers 744.9 — — 744.9 Wholesale revenue Wholesale revenue from contracts with customers 15.8 — (0.7) 15.1 RTO ancillary revenue 88.4 0.1 — 88.5 Capacity revenue 3.5 — — 3.5 Miscellaneous revenue Miscellaneous revenue from contracts with customers (b) — 9.6 — 9.6 Miscellaneous revenue (0.6) 4.4 (4.4) (0.6) Total revenue $ 852.0 $ 14.1 $ (5.1) $ 861.0 $ in millions Utility Other Adjustments and Eliminations Total Year ended December 31, 2022 Retail revenue Retail revenue from contracts with customers Residential revenue $ 467.3 $ — $ — $ 467.3 Commercial revenue 166.0 — — 166.0 Industrial revenue 74.3 — — 74.3 Governmental revenue 24.1 — — 24.1 Other (a) 11.9 — — 11.9 Total retail revenue from contracts with customers 743.6 — — 743.6 Wholesale revenue Wholesale revenue from contracts with customers 41.0 — (0.8) 40.2 RTO ancillary revenue 63.6 0.1 — 63.7 Capacity revenue 4.3 — — 4.3 Miscellaneous revenue Miscellaneous revenue from contracts with customers (b) — 9.6 — 9.6 Miscellaneous revenue 7.6 3.6 (3.6) 7.6 Total revenue $ 860.1 $ 13.3 $ (4.4) $ 869.0 $ in millions Utility Other Adjustments and Eliminations Total Year ended December 31, 2021 Retail revenue Retail revenue from contracts with customers Residential revenue $ 364.9 $ — $ — $ 364.9 Commercial revenue 122.6 — — 122.6 Industrial revenue 57.5 — — 57.5 Governmental revenue 26.1 — — 26.1 Other (a) 12.2 — — 12.2 Total retail revenue from contracts with customers 583.3 — — 583.3 Wholesale revenue Wholesale revenue from contracts with customers 19.5 — (0.7) 18.8 RTO ancillary revenue 49.9 0.1 — 50.0 Capacity revenue 5.9 — — 5.9 Miscellaneous revenue Miscellaneous revenue from contracts with customers (b) — 9.6 — 9.6 Miscellaneous revenue 5.1 3.5 (3.5) 5.1 Total revenue $ 663.7 $ 13.2 $ (4.2) $ 672.7 (a) "Other" primarily includes operation and maintenance service revenue, billing service fees from CRES providers and other miscellaneous retail revenue from contracts with customers. (b) Miscellaneous revenue from contracts with customers primarily includes revenue for various services provided by Miami Valley Lighting. The balances of receivables from contracts with customers were $90.4 million and $85.3 million as of December 31, 2023 and 2022, respectively. Payment terms for all receivables from contracts with customers are typically within 30 days. We have elected to apply the optional disclosure exemptions under ASC 606. Therefore, we have no disclosures pertaining to revenue expected to be recognized in any future year related to remaining performance obligations, as we exclude contracts with an original length of one year or less, contracts for which we recognize revenue based on the amount we have the right to invoice for services performed, and variable consideration allocated entirely to a wholly unsatisfied performance obligation when the consideration relates specifically to our efforts to satisfy the performance obligation and depicts the amount to which we expect to be entitled for DPL.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenue from Contract with Customer [Text Block]	REVENUE Revenue is primarily earned from retail and wholesale electricity sales and electricity transmission and distribution delivery services. Revenue is recognized upon transfer of control of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. Revenue is recorded net of any taxes assessed on and collected from customers, which are remitted to the governmental authorities. Retail revenue AES Ohio energy sales to utility customers are based on the reading of meters at the customer's location that occurs on a systematic basis throughout the month. AES Ohio sells electricity directly to end-users, such as homes and businesses, and bills customers directly. Performance obligations for retail revenue are satisfied over time as energy is delivered and the same method is used to measure progress, and thus the performance obligation meets the criteria to be considered a series. This includes both the promise to transfer energy and other distribution and/or transmission services. In exchange for the exclusive right to sell or distribute electricity in our service area, AES Ohio is subject to rate regulation by federal and state regulators. This regulation sets the framework for the prices (“tariffs”) that AES Ohio is allowed to charge customers for electricity. Since tariffs are approved by the regulator, the price that AES Ohio has the right to bill corresponds directly with the value to the customer of AES Ohio's performance completed in each period. Therefore, revenue under these contracts is recognized using an output method measured by the MWhs delivered each month at the approved tariff. In cases where a customer chooses to receive generation services from a CRES provider, the price for generation services is negotiated between the customer and the CRES provider, and AES Ohio only serves as a billing agent if requested by the CRES provider. As such, AES Ohio recognizes the consolidated billing arrangement with the CRES provider on a net basis, thereby recording no revenue for the generation component. Retail revenue from these customers would only be related to transmission and distribution charges. Wholesale revenue AES Ohio's share of the power produced at OVEC is sold to PJM and this revenue is classified as Wholesale revenue. In PJM, the promise to sell energy as wholesale revenue is separately identifiable from participation in the capacity market and the two products can be transacted independently of one another. Therefore, wholesale revenue is a separate contract with a single performance obligation. Revenue is recorded based on the quantities (MWh) delivered in each hour during each month at the spot price, making the contract effectively “month-to-month”. RTO ancillary revenue Compensation for use of AES Ohio’s transmission assets and compensation for various ancillary services are classified as RTO ancillary revenue. As AES Ohio owns and operates transmission lines in southwest Ohio within PJM, demand charges collected from network customers by PJM are then allocated to the appropriate transmission owners (i.e. AES Ohio) and recognized as transmission revenue. Transmission revenue has a single performance obligation, as transmission services represent a distinct service. Additionally, as the performance obligation is satisfied over time and the same method is used to measure progress, the performance obligation meets the criteria to be considered a series. The price that AES Ohio, as the transmission operator, has the right to bill (received as a credit from PJM) corresponds directly with the value to the customer of performance completed in each period, as the price paid is the allocation of the tariff rate (as approved by the regulator) charged to network participants. Capacity revenue AES Ohio records its share of OVEC capacity revenue as Capacity revenue. The capacity price is set through a competitive auction process established by PJM. Depending on the availability and performance of the OVEC units, there may be additional performance bonuses or penalties, which would be recognized only if it becomes probable that such bonus or penalties will be incurred. RTO capacity revenue has a single performance obligation, as capacity is a distinct good. Additionally, as the performance obligation is satisfied over time and the same method is used to measure progress, the performance obligation meets the criteria to be considered a series. The capacity price is set through a competitive auction process established by PJM. AES Ohio's revenue from contracts with customers was $852.6 million, $852.5 million and $658.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. The following table presents our revenue from contracts with customers and other revenue for the years ended December 31, 2023, 2022 and 2021: Years ended December 31, $ in millions 2023 2022 2021 Retail revenue Retail revenue from contracts with customers Residential revenue $ 478.9 $ 467.3 $ 364.9 Commercial revenue 162.1 166.0 122.6 Industrial revenue 66.6 74.3 57.5 Governmental revenue 24.3 24.1 26.1 Other (a) 13.0 11.9 12.2 Total retail revenue from contracts with customers 744.9 743.6 583.3 Wholesale revenue Wholesale revenue from contracts with customers 15.8 41.0 19.5 RTO ancillary revenue 88.4 63.6 49.9 Capacity revenue 3.5 4.3 5.9 Miscellaneous revenue (0.6) 7.6 5.1 Total revenue $ 852.0 $ 860.1 $ 663.7 (a) "Other" primarily includes operation and maintenance service revenue, billing service fees from CRES providers and other miscellaneous retail revenue from contracts with customers. The balances of receivables from contracts with customers were $89.4 million and $84.6 million as of December 31, 2023 and 2022, respectively. Payment terms for all receivables from contracts with customers are typically within 30 days. We have elected to apply the optional disclosure exemptions under ASC 606. Therefore, we have no disclosures pertaining to revenue expected to be recognized in any future year related to remaining performance obligations, as we exclude contracts with an original length of one year or less, contracts for which we recognize revenue based on the amount we have the right to invoice for services performed, and variable consideration allocated entirely to a wholly unsatisfied performance obligation when the consideration relates specifically to our efforts to satisfy the performance obligation and depicts the amount to which we expect to be entitled for AES Ohio .

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2023
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	DISCONTINUED OPERATIONS In May 2020, AEP, the operator of the formerly co-owned Conesville EGU, retired Conesville Unit 4 as planned. On June 5, 2020, DPL and AES Ohio Generation, together with AEP, completed the transfer of their interests in the retired Unit 4, including the associated environmental liabilities, to an unaffiliated third-party purchaser. For the transaction, DPL made quarterly cash expenditures, totaling $4.0 million, through June 2022. The transfer of Conesville Unit 4 was the last step in DPL's plan to exit its AES Ohio Generation business operations. DPL determined that the transfer of Conesville and the previous transfers and sales of other AES Ohio Generation assets constitute the disposal of a group of components, which, as a whole, represent a strategic shift to exit its AES Ohio Generation business. As such, the disposal of this group of components qualifies to be presented as discontinued operations. Therefore, the results of operations of this group of components were reported as such in the Consolidated Statements of Operations for the period presented. The following table summarizes the revenue, operating costs, other expenses and income tax of discontinued operations for the period indicated: $ in millions 2021 Revenue $ 1.4 Operating costs and other expenses (2.4) Loss from discontinued operations (1.0) Income tax benefit from discontinued operations (0.2) Net loss from discontinued operations $ (0.8) Cash flows related to discontinued operations are included in our Consolidated Statements of Cash Flows. Cash flows from operating activities for discontinued operations were $(0.8) million for the year ended December 31, 2021. Cash flows from investing activities for discontinued operations were $(1.6) million for the year ended December 31, 2021.

Dispositions (Notes)

Dispositions (Notes)	12 Months Ended
	Dec. 31, 2023
Discontinued Operations	DISCONTINUED OPERATIONS In May 2020, AEP, the operator of the formerly co-owned Conesville EGU, retired Conesville Unit 4 as planned. On June 5, 2020, DPL and AES Ohio Generation, together with AEP, completed the transfer of their interests in the retired Unit 4, including the associated environmental liabilities, to an unaffiliated third-party purchaser. For the transaction, DPL made quarterly cash expenditures, totaling $4.0 million, through June 2022. The transfer of Conesville Unit 4 was the last step in DPL's plan to exit its AES Ohio Generation business operations. DPL determined that the transfer of Conesville and the previous transfers and sales of other AES Ohio Generation assets constitute the disposal of a group of components, which, as a whole, represent a strategic shift to exit its AES Ohio Generation business. As such, the disposal of this group of components qualifies to be presented as discontinued operations. Therefore, the results of operations of this group of components were reported as such in the Consolidated Statements of Operations for the period presented. The following table summarizes the revenue, operating costs, other expenses and income tax of discontinued operations for the period indicated: $ in millions 2021 Revenue $ 1.4 Operating costs and other expenses (2.4) Loss from discontinued operations (1.0) Income tax benefit from discontinued operations (0.2) Net loss from discontinued operations $ (0.8) Cash flows related to discontinued operations are included in our Consolidated Statements of Cash Flows. Cash flows from operating activities for discontinued operations were $(0.8) million for the year ended December 31, 2021. Cash flows from investing activities for discontinued operations were $(1.6) million for the year ended December 31, 2021.

Schedule II Valuation And Quali

Schedule II Valuation And Qualifying Accounts	12 Months Ended
	Dec. 31, 2023
Schedule II Valuation And Qualifying Accounts	DPL Inc. VALUATION AND QUALIFYING ACCOUNTS For each of the three years in the period ended December 31, 2023 $ in millions Description Balance at Additions Deductions - Balance at Deducted from accounts receivable Provision for uncollectible accounts Year ended December 31, 2023 $ 0.5 $ 5.4 $ 5.0 $ 0.9 Year ended December 31, 2022 $ 0.3 $ 2.5 $ 2.3 $ 0.5 Year ended December 31, 2021 $ 2.8 $ (0.4) $ 2.1 $ 0.3 Valuation allowance for deferred tax assets Deducted from deferred tax assets - Year ended December 31, 2023 $ 36.6 $ 0.7 $ 1.6 $ 35.7 Year ended December 31, 2022 $ 37.1 $ — $ 0.5 $ 36.6 Year ended December 31, 2021 $ 39.0 $ 1.5 $ 3.4 $ 37.1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Schedule II Valuation And Qualifying Accounts	AES Ohio VALUATION AND QUALIFYING ACCOUNTS For each of the three years in the period ended December 31, 2023 $ in millions Description Balance at Additions Deductions - Balance at Deducted from accounts receivable Provision for uncollectible accounts Year ended December 31, 2023 $ 0.5 $ 5.4 $ 5.0 $ 0.9 Year ended December 31, 2022 $ 0.3 $ 2.5 $ 2.3 $ 0.5 Year ended December 31, 2021 $ 2.8 $ (0.4) $ 2.1 $ 0.3

Overview and Summary of Signi_2

Overview and Summary of Significant Accounting Policies (Policy)	12 Months Ended
	Dec. 31, 2023
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Impairment	GAAP requires that we test long-lived assets for impairment when indicators of impairment exist. If an asset is deemed to be impaired, we are required to write down the asset to its fair value with a charge to current earnings. The net book value of our property, plant, and equipment was $2,221.0 million and $1,885.0 million as of December 31, 2023 and 2022, respectively. We do not believe any of these assets are currently impaired. In making this assessment, we consider such factors as: the overall condition and distribution capacity of the assets; the expected ability to recover additional expenditures in the assets; and the anticipated demand and relative pricing of retail electricity in our service territory.
Debt, Policy [Policy Text Block]	Costs incurred in connection with the issuance of long-term debt are deferred and presented as a direct reduction from the face amount of that debt and amortized over the related financing period using the effective interest method. Debt issuance costs related to a line-of-credit or revolving credit facility are deferred and presented as an asset and amortized over the related financing period. Make-whole payments in connection with early debt retirements are classified as cash flows from financing activities.
Financial Statement Presentation	DPL’s Consolidated Financial Statements include the accounts of DPL and its wholly-owned subsidiaries, except for DPL Capital Trust II, which is not consolidated consistent with the provisions of GAAP. All material intercompany accounts and transactions are eliminated in consolidation. We have evaluated subsequent events through the date this report was issued.
Reclassifications	Certain amounts from prior periods have been reclassified to conform to the current period presentation.
Discontinued Operations, Policy [Policy Text Block]	Discontinued operations reporting occurs only when the disposal of a business or a group of assets represents a strategic shift that has (or will have) a major effect on our operations and financial results. We report financial results for discontinued operations separately from continuing operations to distinguish the financial impact of disposal transactions from ongoing operations. Prior period amounts in the Consolidated Statements of Operations and Consolidated Balance Sheets are retrospectively revised to reflect the businesses determined to be discontinued operations. The cash flows of businesses that are determined to be discontinued operations are included within the relevant categories within operating, investing and financing activities on the face of the Consolidated Statements of Cash Flows. Transactions between the businesses determined to be discontinued operations and businesses that are expected to continue to exist after the disposal are not eliminated to appropriately reflect the continuing operations and balances held-for-sale. The results of discontinued operations include any gain or loss recognized on closing or adjustment of the carrying amount to fair value. See Note 14. Discontinued Operations for further information.
Use of Estimates	The preparation of consolidated financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities and the revenue and expenses of the periods reported. Actual results could differ from these estimates and assumptions. Significant items subject to such estimates and assumptions include: the carrying value of Property, plant and equipment; unbilled revenue; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; reserves recorded for income tax exposures; litigation; contingencies; and assets and liabilities related to employee benefits.
Revenue Recognition	Revenue is recognized from retail and wholesale electricity sales and electricity transmission and distribution delivery services. Revenue is recognized upon transfer of control of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. Energy sales to customers are based on the reading of their meters that occurs on a systematic basis throughout the month. We recognize the revenue on our Consolidated Statements of Operations using an accrual method for retail and other energy sales that have not yet been billed, but where electricity has been consumed. This is termed “unbilled revenue” and is a widely recognized and accepted practice for utilities. At the end of each month, unbilled revenue is determined by the estimation of unbilled energy provided to customers since the date of the last meter reading, estimated line losses, the assignment of unbilled energy provided to customer classes and the average rate per customer class. For more information, see Note 13. Revenue .
Property, Plant and Equipment	New property, plant and equipment additions are stated at cost. For regulated transmission and distribution property, cost includes direct labor and material, allocable overhead expenses and AFUDC. AFUDC represents the cost of borrowed funds and equity used to finance regulated construction projects. Capitalization of AFUDC and interest ceases at either project completion or at the date specified by regulators. For substantially all depreciable property, when a unit of property is retired, the original cost of that property, less any salvage value, is charged to Accumulated depreciation and amortization
Repairs and Maintenance	Costs associated with maintenance activities are recognized at the time the work is performed. These costs, which include labor, materials and supplies and outside services required to maintain equipment and facilities, are capitalized or expensed based on defined units of property.
Regulatory Accounting	As a regulated utility, AES Ohio applies the provisions of ASC 980 - Regulated Operations , which gives recognition to the ratemaking and accounting practices of the PUCO and the FERC. Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates. Regulatory assets can also represent performance incentives permitted by the regulator. Regulatory assets have been included as allowable costs for ratemaking purposes, as authorized by the PUCO or established regulatory practices. Regulatory liabilities generally represent obligations to make refunds or future rate reductions to customers for previous over collections or the deferral of revenue collected for costs that AES Ohio expects to incur in the future. The deferral of costs (as regulatory assets) is appropriate only when the future recovery of such costs is probable. In assessing probability, we consider such factors as specific orders from the PUCO or the FERC, regulatory precedent and the current regulatory environment. To the extent recovery of costs is no longer deemed probable, related regulatory assets would be required to be expensed in current period earnings. Our regulatory assets and liabilities have been created pursuant to a specific order of the PUCO or the FERC or established regulatory practices, such as other utilities under the jurisdiction of the PUCO or the FERC being granted recovery of similar costs. It is probable, but not certain, that these regulatory assets will be recoverable, subject to approval by the PUCO or the FERC. Regulatory assets and liabilities are classified as current or non-current based on the term in which recovery is expected. See Note 2. Regulatory Matters for more information.
Inventories	Inventories are carried at average cost, net of reserves, and consist of materials and supplies used for utility operations.
Intangibles	Intangibles include software and renewable energy credits. Renewable energy credits are carried on a weighted average cost basis and amortized as they are used or retired. Finite-lived intangible assets include capitalized software amortized on a straight-line basis over their estimated useful lives. These capitalized software intangible assets have a seven year-weighted average amortization period. The following table presents information related to the Company's capitalized software balances, including the gross amount capitalized and related amortization: December 31, $ in millions 2023 2022 Capitalized software $ 146.5 $ 105.0 Accumulated amortization $ (32.5) $ (36.1) Years ended December 31, 2023 2022 2021 Amortization expense $ 4.1 $ 3.3 $ 3.2 Estimated future amortization Years ending December 31, 2024 $ 6.3 2025 6.3 2026 5.9 2027 5.3 2028 4.9 Total $ 28.7
Income Taxes	Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the consolidated financial statement carrying amounts of the existing assets and liabilities and their respective income tax bases. We establish an allowance when it is more likely than not that all or a portion of a deferred tax asset will not be realized. Our tax positions are evaluated under a more likely than not recognition threshold and measurement analysis before they are recognized for consolidated financial statement reporting. Uncertain tax positions have been classified as noncurrent income tax liabilities unless expected to be paid within one year. Our policy for interest and penalties is to recognize interest and penalties as a component of the provision for income taxes in the Consolidated Statements of Operations. Income taxes payable, which are includable in allowable costs for ratemaking purposes in future years, are recorded as regulatory assets or liabilities with a corresponding deferred tax liability or asset. Investment tax credits that reduced federal income taxes in the years they arose have been deferred and are being amortized to income over the useful lives of the properties in accordance with regulatory treatment. See Note 2. Regulatory Matters for more information. DPL and its subsidiaries file U.S. federal income tax returns as part of the consolidated U.S. income tax return filed by AES. The consolidated tax liability is allocated to each subsidiary based on the separate return method as specified in our tax allocation agreement, and which provides a consistent, systematic and rational approach. See Note 7. Income Taxes for more information.
Financial Instruments	Our Master Trust investments in debt and equity financial instruments of publicly traded entities are classified as equity investments. These equity securities are carried at fair value and unrealized gains and losses on these securities are recorded in Other income . As these financial instruments are held to be used for the benefit of employees or former employees participating in employee benefit plans and are not used for general operating purposes, they are recorded within Other non-current assets
Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities	collects certain excise taxes levied by state or local governments from its customers. AES Ohio’s excise taxes and certain other taxes are accounted for on a net basis and recorded as a reduction in revenue in the accompanying Consolidated Statements of Operations. The amounts of such taxes were as follows:
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are stated at cost, which approximates fair value. All highly liquid short-term investments with original maturities of three months or less are considered cash equivalents. Restricted Cash
Financial Derivatives	Financial Derivatives We have contracts involving the physical delivery of energy. These contracts qualify for the normal purchases and normal sales scope exception in ASC 815 - Derivatives and Hedging , thus we have elected to account for them as accrual contracts, which are not adjusted for changes in fair value. We have, in the past, used interest rate hedges to manage the interest rate risk of our variable rate debt. We used cash flow hedge accounting when the hedge or a portion of the hedge was deemed to be highly effective, which resulted in changes in fair value being recorded within accumulated other comprehensive loss, a component of shareholder’s equity / (deficit). We elected not to offset net derivative positions in the consolidated financial statements. Accordingly, we did not offset such derivative positions against the fair value of amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral under master netting agreements. See Note 5. Derivative Instruments and Hedging Activities for more information.
Insurance and Claims Costs	Insurance and Claims Costs In addition to insurance obtained from third-party providers, MVIC, a wholly-owned captive subsidiary of DPL, provides insurance coverage solely to us and our subsidiaries for workers’ compensation, general liability and property damage on an ongoing basis. Insurance and claims costs associated with MVIC include estimated liabilities of approximately $1.8 million and $1.6 million at December 31, 2023 and 2022, respectively, within Accrued and other current liabilities on the accompanying Consolidated Balance Sheets. DPL has estimated liabilities for medical, life, disability and other reserves for claims costs below certain coverage thresholds of third-party providers of approximately $8.0 million and $7.8 million at December 31, 2023 and 2022, respectively, within Accrued and other current liabilities and Other non-current liabilities on the accompanying Consolidated Balance Sheets. The estimated liabilities for workers’ compensation, medical, life and disability costs at DPL are actuarially determined using certain assumptions. There is uncertainty associated with these loss estimates, and actual results may differ from the estimates. Modification of these loss estimates based on experience and changed circumstances is reflected in the period in which the estimate is re-evaluated.
Pension and Postretirement Benefits	We recognize in our Consolidated Balance Sheets an asset or liability reflecting the funded status of pension and other postretirement plans with current-year changes from actuarial gains or losses related to our regulated operations, which would otherwise be recognized in AOCL, recorded as a regulatory asset as this can be recovered through future rates. Such changes that are not related to our regulated operations are recognized in AOCL. All plan assets are recorded at fair value. We follow the measurement date provisions of the accounting guidance, which require a year-end measurement date of plan assets and obligations for all defined benefit plans. We account for and disclose pension and postretirement benefits in accordance with the provisions of GAAP relating to the accounting for pension and other postretirement plans. These GAAP provisions require the use of assumptions, such as the discount rate for liabilities and long-term rate of return on assets, in determining the obligations, annual cost and funding requirements of the plans. Consistent with the requirements of ASC 715 - Compensation - Retirement Benefits , we apply a disaggregated discount rate approach for determining service cost and interest cost for our defined benefit pension plans and postretirement plans. See Note 8. Benefit Plans for more information.
Related Party Transactions	In the normal course of business, DPL enters into transactions with related parties. All material intercompany accounts and transactions are eliminated in DPL’s Consolidated Financial Statements. See Note 11. Related Party Transactions for more information.
Recently Issued Accounting Standards	New accounting pronouncements The following table provides a brief description of recent accounting pronouncements that could have an impact on our consolidated financial statements. Accounting pronouncements not listed below were assessed and determined to be either not applicable or did not have a material impact on our Consolidated Financial Statements. ASU Number and Name Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Issued But Not Yet Effective 2023-06 Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative In U.S. Securities and Exchange Commission (SEC) Release No. 33-10532, Disclosure Update and Simplification, issued August 17, 2018, the SEC referred certain of its disclosure requirements that overlap with, but require incremental information to, generally accepted accounting principles (GAAP) to the FASB for potential incorporation into the Codification. The amendments in this Update are the result of the Board’s decision to incorporate into the Codification 14 of the 27 disclosures referred by the SEC. The amendments in this Update represent changes to clarify or improve disclosure and presentation requirements of a variety of Topics. Many of the amendments allow users to more easily compare entities subject to the SEC’s existing disclosures with those entities that were not previously subject to the SEC’s requirements. Also, the amendments align the requirements in the Codification with the SEC’s regulations. The effective date for each amendment will be the date on which the SEC's removal of that related disclosure becomes effective, with early adoption prohibited. The amendments in this Update should be applied prospectively We will provide the required disclosures on a prospective basis on the date each amendment becomes effective. We do not expect ASU 2023-06 will have any impact on our Consolidated Financial Statements. 2023-07 Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures The amendments in this section are designed to improve the disclosures related to Segment reporting on an interim and annual basis. Public companies must disclose significant segment expenses and an amount for other segment items. This will also require that a company disclose its annual disclosures under Topic 280 in each interim period. Furthermore, companies will need to disclose the Chief Operating Decision Maker (CODM) and how the CODM assesses the performance of a segment. Lastly, public companies that have a single reportable segment must report the required disclosures under topic 280. The amendments in this Update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our Consolidated Financial Statements. 2023-09 Income Taxes (Topic 740): Improvements to Income Tax Disclosures The amendments in this Update require that public business entities on an annual basis (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. Furthermore, companies are required to disclose a disaggregated amount of income taxes paid at a federal, state, and foreign level as well as a break down of income taxes paid in an jurisdiction that comprises 5% of a company's total income taxes paid. Lastly, this ASU requires that companies disclose income (loss) from continuing operations before income tax at a domestic and foreign level and that companies disclose income tax expense from continuing operations on a federal, state, and foreign level. The amendments in this Update are effective for fiscal years beginning after December 15, 2024 We are currently evaluating the impact of adopting the standard on our Consolidated Financial Statements.
Consolidation, Variable Interest Entity, Policy [Policy Text Block]	In addition to the obligations under the note payable mentioned above, DPL also agreed to a security obligation, which represents a full and unconditional guarantee of payments to the capital security holders of the Master Trust.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Impairment	GAAP requires that we test long-lived assets for impairment when indicators of impairment exist. If an asset is deemed to be impaired, we are required to write down the asset to its fair value with a charge to current earnings. The net book value of our property, plant, and equipment was $2,195.9 million and $1,861.5 million as of December 31, 2023 and 2022, respectively. We do not believe any of these assets are currently impaired. In making this assessment, we consider such factors as: the overall condition and distribution capacity of the assets; the expected ability to recover additional expenditures in the assets; and the anticipated demand and relative pricing of retail electricity in our service territory.
Debt, Policy [Policy Text Block]	Costs incurred in connection with the issuance of long-term debt are deferred and presented as a direct reduction from the face amount of that debt and amortized over the related financing period using the effective interest method. Debt issuance costs related to a line-of-credit or revolving credit facility are deferred and presented as an asset and amortized over the related financing period. Make-whole payments in connection with early debt retirements are classified as cash flows from financing activities.
Description of Business	is a public utility incorporated in 1911 under the laws of Ohio. Beginning in 2001, Ohio law gave consumers the right to choose the electric generation supplier from whom they purchase retail generation service; however, transmission and distribution services are still regulated. AES Ohio has the exclusive right to provide such service to its approximately 539,000 customers located in West Central Ohio. Principal industries located in AES Ohio’s service territory include automotive, food processing, paper, plastic, manufacturing and defense. AES Ohio also provides retail SSO electric service to residential, commercial, industrial and governmental customers in a 6,000 square mile area of West Central Ohio. AES Ohio sources all of the generation for its SSO customers through a competitive bid process AES Ohio's sales reflect the general economic conditions, seasonal weather patterns of the area, the market price of electricity and customer energy efficiency initiatives. AES Ohio owns numerous transmission facilities. AES Ohio records revenue and expenses for its proportional share of energy and capacity from its investment in OVEC. AES Ohio has only one reportable segment, the Utility segment. In addition to AES Ohio's electric transmission and distribution businesses, the Utility segment includes revenue and costs associated with AES Ohio's investment in OVEC. The terms “we,” “us,” “our” and “ours” are used to refer to AES Ohio. AES Ohio’s electric transmission and distribution businesses are subject to rate regulation by federal and state regulators. Accordingly, AES Ohio applies the accounting standards for regulated operations to its electric transmission and distribution businesses and records regulatory assets when incurred costs are expected to be recovered in future customer rates and regulatory liabilities when current cost recoveries in customer rates relate to expected future costs or overcollections of riders.
Financial Statement Presentation	does not have any subsidiaries. We have evaluated subsequent events through the date this report was issued. Reclassifications
Reclassifications	Certain amounts from prior periods have been reclassified to conform to the current period presentation.
Use of Estimates	The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities and the revenue and expenses of the periods reported. Actual results could differ from these estimates and assumptions. Significant items subject to such estimates and assumptions include: the carrying value of Property, plant and equipment; unbilled revenue; the valuation of allowances for receivables and deferred income taxes; regulatory assets and liabilities; reserves recorded for income tax exposures; litigation; contingencies; and assets and liabilities related to employee benefits.
Property, Plant and Equipment	New property, plant and equipment additions are stated at cost. For regulated transmission and distribution property, cost includes direct labor and material, allocable overhead expenses and AFUDC. AFUDC represents the cost of borrowed funds and equity used to finance regulated construction projects. Capitalization of AFUDC and interest ceases at either project completion or at the date specified by regulators. For substantially all depreciable property, when a unit of property is retired, the original cost of that property, less any salvage value, is charged to Accumulated depreciation and amortization , consistent with composite depreciation practices. Depreciation expense is calculated using the straight-line method, which allocates the cost of property over its estimated useful life. For AES Ohio’s transmission and distribution assets, straight-line depreciation is applied monthly on an average composite basis using group rates that approximated 2.6% in 2023, 2.8% in 2022 and 2.8% in 2021. Depreciation expense was $76.8 million, $75.6 million and $71.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. AFUDC In accordance with the Uniform System of Accounts prescribed by FERC, AES Ohio capitalizes an allowance for the net cost of funds (interest on borrowed funds and a reasonable rate of return on equity funds) used for construction purposes during the period of construction with a corresponding credit to income. AFUDC equity and AFUDC debt were as follows for the years ended December 31, 2023, 2022 and 2021: Years ended December 31, $ in millions 2023 2022 2021 AFUDC equity $ 5.0 $ 5.7 $ 2.1 AFUDC debt $ 6.5 $ 1.3 $ 1.6
Regulatory Accounting	As a regulated utility, AES Ohio applies the provisions of ASC 980 - Regulated Operations , which gives recognition to the ratemaking and accounting practices of the PUCO and the FERC. Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates. Regulatory assets can also represent performance incentives permitted by the regulator. Regulatory assets have been included as allowable costs for ratemaking purposes, as authorized by the PUCO or established regulatory practices. Regulatory liabilities generally represent obligations to make refunds or future rate reductions to customers for previous over collections or the deferral of revenue collected for costs that AES Ohio expects to incur in the future. The deferral of costs (as regulatory assets) is appropriate only when the future recovery of such costs is probable. In assessing probability, we consider such factors as specific orders from the PUCO or the FERC, regulatory precedent and the current regulatory environment. To the extent recovery of costs is no longer deemed probable, related regulatory assets would be required to be expensed in current period earnings. Our regulatory assets and liabilities have been created pursuant to a specific order of the PUCO or the FERC or established regulatory practices, such as other utilities under the jurisdiction of the PUCO or the FERC being granted recovery of similar costs. It is probable, but not certain, that these regulatory assets will be recoverable, subject to approval by the PUCO or the FERC. Regulatory assets and liabilities are classified as current or non-current based on the term in which recovery is expected. See Note 2. Regulatory Matters for more information.
Inventories	nventories are carried at average cost, net of reserves, and include materials and supplies used for utility operations.
Intangibles	Intangibles include software and renewable energy credits. Renewable energy credits are carried on a weighted average cost basis and amortized as they are used or retired. Finite-lived intangible assets include capitalized software amortized on a straight-line basis over their estimated useful lives. These capitalized software intangible assets have a seven year-weighted average amortization period. The following table presents information related to the Company's capitalized software balances, including the gross amount capitalized and related amortization: December 31, $ in millions 2023 2022 Capitalized software $ 142.2 $ 101.5 Accumulated amortization $ (30.8) $ (34.3) Years ended December 31, 2023 2022 2021 Amortization expense $ 3.9 $ 3.1 $ 3.0 Estimated future amortization Years ending December 31, 2024 $ 5.6 2025 5.6 2026 5.2 2027 4.6 2028 4.4 Total $ 25.4
Financial Instruments	Our Master Trust investments in debt and equity financial instruments of publicly traded entities are classified as equity investments. These equity securities are carried at fair value and unrealized gains and losses on these securities are recorded in Other income . As these financial instruments are held to be used for the benefit of employees or former employees participating in employee benefit plans and are not used for general operating purposes, they are recorded within Other non-current assets on the accompanying Balance Sheets. See Note 4. Fair Value for more information.
Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities	Years ended December 31, $ in millions 2023 2022 2021 Excise taxes collected $ 46.6 $ 49.2 $ 48.7
Cash and Cash Equivalents	Cash and cash equivalents are stated at cost, which approximates fair value. All highly liquid short-term investments with original maturities of three months or less are considered cash equivalents. Restricted Cash Restricted cash includes cash which is restricted as to withdrawal or usage. The nature of the restrictions includes restrictions imposed by agreements related to deposits held as collateral. The following table summarizes cash, cash equivalents and restricted cash amounts reported within the Balance Sheets that reconcile to the total of such amounts as shown on the Statements of Cash Flows: December 31, $ in millions 2023 2022 Cash and cash equivalents $ 15.5 $ 19.7 Restricted cash (included in Prepayments and other current assets ) 0.1 0.1 Total cash, cash equivalents and restricted cash $ 15.6 $ 19.8
Financial Derivatives	We have contracts involving the physical delivery of energy. These contracts qualify for the normal purchases and normal sales scope exception in ASC 815 - Derivatives and Hedging , thus we have elected to account for them as accrual contracts, which are not adjusted for changes in fair value.
Pension and Postretirement Benefits	Income Taxes Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of the existing assets and liabilities and their respective income tax bases. We establish an allowance when it is more likely than not that all or a portion of a deferred tax asset will not be realized. Our tax positions are evaluated under a more likely than not recognition threshold and measurement analysis before they are recognized for financial statement reporting. Uncertain tax positions have been classified as noncurrent income tax liabilities unless expected to be paid within one year. Our policy for interest and penalties is to recognize interest and penalties as a component of the provision for income taxes in the Statements of Operations. Income taxes payable, which are includable in allowable costs for ratemaking purposes in future years, are recorded as regulatory assets or liabilities with a corresponding deferred tax liability or asset. Investment tax credits that reduced federal income taxes in the years they arose have been deferred and are being amortized to income over the useful lives of the properties in accordance with regulatory treatment. See Note 2. Regulatory Matters for more information. AES Ohio files U.S. federal income tax returns as part of the consolidated U.S. income tax return filed by AES. The consolidated tax liability is allocated to each subsidiary based on the separate return method as specified in our tax allocation agreement, and which provides a consistent, systematic and rational approach. See Note 6. Income Taxes for more information.
Recently Issued Accounting Standards	ASU Number and Name Description Date of Adoption Effect on the financial statements upon adoption New Accounting Standards Issued But Not Yet Effective 2023-06 Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative In U.S. Securities and Exchange Commission (SEC) Release No. 33-10532, Disclosure Update and Simplification, issued August 17, 2018, the SEC referred certain of its disclosure requirements that overlap with, but require incremental information to, generally accepted accounting principles (GAAP) to the FASB for potential incorporation into the Codification. The amendments in this Update are the result of the Board’s decision to incorporate into the Codification 14 of the 27 disclosures referred by the SEC. The amendments in this Update represent changes to clarify or improve disclosure and presentation requirements of a variety of Topics. Many of the amendments allow users to more easily compare entities subject to the SEC’s existing disclosures with those entities that were not previously subject to the SEC’s requirements. Also, the amendments align the requirements in the Codification with the SEC’s regulations. The effective date for each amendment will be the date on which the SEC's removal of that related disclosure becomes effective, with early adoption prohibited. The amendments in this Update should be applied prospectively We will provide the required disclosures on a prospective basis on the date each amendment becomes effective. We do not expect ASU 2023-06 will have any impact on our Financial Statements. 2023-07 Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures The amendments in this section are designed to improve the disclosures related to Segment reporting on an interim and annual basis. Public companies must disclose significant segment expenses and an amount for other segment items. This will also require that a company disclose its annual disclosures under Topic 280 in each interim period. Furthermore, companies will need to disclose the Chief Operating Decision Maker (CODM) and how the CODM assesses the performance of a segment. Lastly, public companies that have a single reportable segment must report the required disclosures under topic 280. The amendments in this Update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We are currently evaluating the impact of adopting the standard on our Financial Statements. 2023-09 Income Taxes (Topic 740): Improvements to Income Tax Disclosures The amendments in this Update require that public business entities on an annual basis (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. Furthermore, companies are required to disclose a disaggregated amount of income taxes paid at a federal, state, and foreign level as well as a break down of income taxes paid in an jurisdiction that comprises 5% of a company's total income taxes paid. Lastly, this ASU requires that companies disclose income (loss) from continuing operations before income tax at a domestic and foreign level and that companies disclose income tax expense from continuing operations on a federal, state, and foreign level. The amendments in this Update are effective for fiscal years beginning after December 15, 2024 We are currently evaluating the impact of adopting the standard on our Financial Statements.

Overview and Summary of Signi_3

Overview and Summary of Significant Accounting Policies Overview and Summary of Significant Accounting Polices (Tables)	12 Months Ended
	Dec. 31, 2023
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Schedule of Accounts, Notes, Loans and Financing Receivable	The following table summarizes accounts receivable as of December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Accounts receivable, net Customer receivables $ 71.0 $ 61.3 Unbilled revenue 19.4 24.0 Amounts due from affiliates 0.8 3.2 Other 2.2 3.9 Allowance for credit losses (0.9) (0.5) Total accounts receivable, net $ 92.5 $ 91.9
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The changes in the components of Accumulated other comprehensive loss during the years ended December 31, 2023 and 2022 are as follows: $ in millions Gains / (losses) on cash flow hedges Change in unfunded pension and other postretirement obligations Total Balance at January 1, 2022 $ 12.8 $ (17.6) $ (4.8) Other comprehensive income before reclassifications — 2.2 2.2 Amounts reclassified from accumulated other comprehensive loss to earnings (0.8) 1.0 0.2 Net current period other comprehensive income / (loss) (0.8) 3.2 2.4 Balance at December 31, 2022 12.0 (14.4) (2.4) Other comprehensive loss before reclassifications — (1.6) (1.6) Amounts reclassified from accumulated other comprehensive loss to earnings (0.8) 0.2 (0.6) Net current period other comprehensive loss (0.8) (1.4) (2.2) Balance at December 31, 2023 $ 11.2 $ (15.8) $ (4.6)
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2023, 2022 and 2021 are as follows: Details about AOCL Components Affected line in the Consolidated Statements of Operations Years ended December 31, $ in millions 2023 2022 2021 Gains and losses on cash flow hedges (Note 5): Interest expense, net $ (1.0) $ (1.0) $ (1.0) Income tax effect 0.2 0.2 0.2 Net of income taxes (0.8) (0.8) (0.8) Amortization of unfunded pension and other postretirement obligations (Note 8): Other expense 0.2 1.3 2.5 Income tax effect — (0.3) (0.6) Net of income taxes 0.2 1.0 1.9 Total reclassifications for the period, net of income taxes $ (0.6) $ 0.2 $ 1.1
Accounts Receivable, Allowance for Credit Loss	The following table is a rollforward of our allowance for credit losses related to the accounts receivable balances for the years ended December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Allowance for credit losses: Beginning balance $ 0.5 $ 0.3 Current period provision 5.4 2.5 Write-offs charged against allowance (6.0) (4.1) Recoveries collected 1.0 1.8 Ending balance $ 0.9 $ 0.5 The allowance for credit losses primarily relates to utility customer receivables, including unbilled amounts. Expected credit loss estimates are developed by disaggregating customers into those with similar credit risk characteristics and using historical credit loss experience. In addition, we also consider how current and future economic conditions are expected to impact collectability. Amounts are written off when reasonable collections efforts have been exhausted.
Schedule of Cash and Cash Equivalents [Table Text Block]	The following table summarizes cash, cash equivalents and restricted cash amounts reported within the Consolidated Balance Sheets that reconcile to the total of such amounts as shown on the Consolidated Statements of Cash Flows: December 31, $ in millions 2023 2022 Cash and cash equivalents $ 41.0 $ 30.5 Restricted cash (included in Prepayments and other current assets ) 0.1 0.1 Total cash, cash equivalents and restricted cash $ 41.1 $ 30.6
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Schedule of Accounts, Notes, Loans and Financing Receivable	The following table summarizes accounts receivable as of December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Accounts receivable, net Customer receivables $ 70.0 $ 60.6 Unbilled revenue 19.4 24.0 Amounts due from affiliates 2.4 4.4 Other 2.2 3.8 Allowance for credit losses (0.9) (0.5) Total accounts receivable, net $ 93.1 $ 92.3
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	$ in millions Change in Accumulated other comprehensive loss Balance at January 1, 2022 $ (31.8) Other comprehensive income before reclassifications 2.3 Amounts reclassified from accumulated other comprehensive loss to earnings 2.7 Net current period other comprehensive income 5.0 Balance at December 31, 2022 (26.8) Other comprehensive loss before reclassifications (1.5) Amounts reclassified from accumulated other comprehensive loss to earnings 0.4 Net current period other comprehensive income (1.1) Balance at December 31, 2023 $ (27.9)
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2023, 2022 and 2021 are as follows: Details about AOCL Components Affected line in the Statements of Operations Years ended December 31, $ in millions 2023 2022 2021 Amortization of unfunded pension and other postretirement obligations (Note 7): Other expense $ 0.6 $ 3.6 $ 5.0 Income tax effect (0.2) (0.9) (1.1) Total reclassifications for the period, net of income taxes $ 0.4 $ 2.7 $ 3.9
Accounts Receivable, Allowance for Credit Loss	The following table is a rollforward of our allowance for credit losses related to the accounts receivable balances for the years ended December 31, 2023 and 2022: December 31, $ in millions 2023 2022 Allowance for credit losses: Beginning balance $ 0.5 $ 0.3 Current period provision 5.4 2.5 Write-offs charged against allowances (6.0) (4.1) Recoveries collected 1.0 1.8 Ending balance $ 0.9 $ 0.5
Schedule of Cash and Cash Equivalents [Table Text Block]	The following table summarizes cash, cash equivalents and restricted cash amounts reported within the Balance Sheets that reconcile to the total of such amounts as shown on the Statements of Cash Flows: December 31, $ in millions 2023 2022 Cash and cash equivalents $ 15.5 $ 19.7 Restricted cash (included in Prepayments and other current assets ) 0.1 0.1 Total cash, cash equivalents and restricted cash $ 15.6 $ 19.8

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2023
Schedule of Regulatory Assets and Liabilities [Table Text Block]	The following table presents DPL’s Regulatory assets and liabilities: Type of Recovery Amortization Through December 31, $ in millions 2023 2022 Regulatory assets, current: Undercollections to be collected through rate riders A/B 2024 $ 51.7 $ 38.7 Uncollectible expense being recovered in base rates B 2024 1.7 — Vegetation management being recovered in base rates B 2024 2.7 — Rate case expenses being recovered in base rates B 2024 0.5 0.5 Total regulatory assets, current 56.6 39.2 Regulatory assets, non-current: Pension benefits A/B Ongoing 62.6 64.2 Regulatory compliance costs A 2028 45.0 6.4 Energy efficiency D Undetermined 4.1 — Smart grid and AMI costs B/C Ongoing 3.2 2.3 Unamortized loss on reacquired debt B Ongoing 1.1 2.0 Deferred storm costs B Ongoing 2.2 8.7 Deferred rate case costs B 2028 1.5 1.9 Deferred vegetation management B 2028 19.9 21.9 CIS replacement D Undetermined 3.1 1.1 Transmission formula rate debits B 2025 6.7 — Decoupling deferral A 2028 — 13.8 Uncollectible deferral B 2028 6.3 7.5 Total regulatory assets, non-current 155.7 129.8 Total regulatory assets $ 212.3 $ 169.0 Regulatory liabilities, current: Overcollection of costs to be refunded through rate riders A/B 2024 $ 14.7 $ 27.6 Transmission formula rate credits B 2024 3.3 12.8 Total regulatory liabilities, current 18.0 40.4 Regulatory liabilities, non-current: Estimated costs of removal - regulated property Not Applicable 134.2 136.8 Deferred income taxes payable through rates Ongoing 42.6 45.2 TCJA regulatory liability B Ongoing 1.0 4.5 Transmission formula rate credits B 2024 — 5.4 PJM transmission enhancement settlement B 2025 1.7 3.5 Postretirement benefits B Ongoing 2.6 3.3 Total regulatory liabilities, non-current 182.1 198.7 Total regulatory liabilities $ 200.1 $ 239.1 A – Recovery of incurred costs plus rate of return. B – Recovery of incurred costs without a rate of return. C – Includes costs associated with Smart Grid Phase 2 development for which recovery is not yet determined but is considered probable of occurring in future rate proceedings. D – Recovery not determined, but recovery is probable of occurring in future rate proceedings.
Subsidiaries [Member]
Schedule of Regulatory Assets and Liabilities [Table Text Block]	The following table presents AES Ohio’s Regulatory assets and liabilities: Type of Recovery Amortization Through December 31, $ in millions 2023 2022 Regulatory assets, current: Undercollections to be collected through rate riders A/B 2024 $ 51.7 $ 38.7 Uncollectible expense being recovered in base rates B 2024 1.7 — Vegetation management being recovered in base rates B 2024 2.7 — Rate case expenses being recovered in base rates B 2024 0.5 0.5 Total regulatory assets, current 56.6 39.2 Regulatory assets, non-current: Pension benefits A/B Ongoing 62.6 64.2 Regulatory compliance costs A 2028 45.0 6.4 Energy efficiency D Undetermined 4.1 — Smart grid and AMI costs B/C Ongoing 3.2 2.3 Unamortized loss on reacquired debt B Ongoing 1.1 2.0 Deferred storm costs B Ongoing 2.2 8.7 Deferred rate case costs B 2028 1.5 1.9 Deferred vegetation management B 2028 19.9 21.9 CIS replacement D Undetermined 3.1 1.1 Transmission formula rate debits B 2025 6.7 — Decoupling deferral A 2028 — 13.8 Uncollectible deferral B 2028 6.3 7.5 Total regulatory assets, non-current 155.7 129.8 Total regulatory assets $ 212.3 $ 169.0 Regulatory liabilities, current: Overcollection of costs to be refunded through rate riders A/B 2024 $ 14.7 $ 27.6 Transmission formula rate credits B 2024 3.3 12.8 Total regulatory liabilities, current 18.0 40.4 Regulatory liabilities, non-current: Estimated costs of removal - regulated property Not Applicable 134.2 136.8 Deferred income taxes payable through rates Ongoing 42.6 45.2 TCJA regulatory liability B Ongoing 1.0 4.5 Transmission formula rate credits B 2024 — 5.4 PJM transmission enhancement settlement B 2025 1.7 3.5 Postretirement benefits B Ongoing 2.6 3.3 Total regulatory liabilities, non-current 182.1 198.7 Total regulatory liabilities $ 200.1 $ 239.1 A – Recovery of incurred costs plus rate of return. B – Recovery of incurred costs without a rate of return. C – Includes costs associated with Smart Grid Phase 2 development for which recovery is not yet determined but is considered probable of occurring in future rate proceedings. D – Recovery not determined, but recovery is probable of occurring in future rate proceedings.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Summary of Property, Plant, and Equipment	The following is a summary of DPL’s Property, plant and equipment with corresponding composite depreciation rates at December 31, 2023 and 2022: December 31, 2023 December 31, 2022 $ in millions Composite Rate Composite Rate Regulated: Transmission $ 505.3 2.5% $ 399.2 2.4% Distribution 1,860.9 3.5% 1,658.9 3.7% General 19.3 5.9% 20.7 5.2% Non-depreciable 99.5 N/A 79.4 N/A Total regulated 2,485.0 2,158.2 Unregulated: Other 31.3 4.1% 30.6 3.7% Non-depreciable 5.6 N/A 4.8 N/A Total unregulated 36.9 35.4 Total property, plant and equipment in service $ 2,521.9 3.2% $ 2,193.6 3.3%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Property, Plant and Equipment [Line Items]
Summary of Property, Plant, and Equipment	The following is a summary of AES Ohio’s Property, plant and equipment with corresponding composite depreciation rates at December 31, 2023 and 2022: December 31, 2023 December 31, 2022 $ in millions Composite Rate Composite Rate Regulated: Transmission $ 648.0 2.0% $ 545.3 2.0% Distribution 2,283.4 2.9% 2,093.8 3.1% General 32.2 3.5% 34.2 4.0% Non-depreciable 99.6 N/A 79.4 N/A Total property, plant and equipment in service $ 3,063.2 2.6% $ 2,752.7 2.8%

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Entity Information [Line Items]
Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis	The following table presents the carrying amount, fair value, and fair value hierarchy of our financial liabilities that are not measured at fair value in the Consolidated Balance Sheets as of the periods indicated, but for which fair value is disclosed: Carrying Amount Fair Value at December 31, 2023 Carrying Amount Fair Value at December 31, 2022 $ in millions Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Long-term debt $ 1,837.6 $ — $ 1,706.2 $ 16.8 $ 1,723.0 $ 1,535.9 $ — $ 1,376.4 $ 17.0 $ 1,393.4
Fair Value, Assets Measured on Recurring Basis	The fair value of assets at December 31, 2023 and 2022 and the respective category within the fair value hierarchy for DPL was determined as follows: $ in millions Fair Value at December 31, 2023 Fair Value at December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Master trust assets Money market funds $ 0.6 $ — $ — $ 0.6 $ 0.5 $ — $ — $ 0.5 Mutual funds 7.2 — — 7.2 7.0 — — 7.0 Total assets $ 7.8 $ — $ — $ 7.8 $ 7.5 $ — $ — $ 7.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis	The following table presents the carrying amount, fair value, and fair value hierarchy of our financial liabilities that are not measured at fair value in the Balance Sheets as of the periods indicated, but for which fair value is disclosed: Carrying Amount Fair Value at December 31, 2023 Carrying Amount Fair Value at December 31, 2022 $ in millions Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Long-term debt $ 1,012.5 $ — $ 909.9 $ 16.8 $ 926.7 $ 712.7 $ — $ 610.9 $ 17.0 $ 627.9
Fair Value, Assets Measured on Recurring Basis	The fair value of assets at December 31, 2023 and 2022 and the respective category within the fair value hierarchy for AES Ohio was determined as follows: $ in millions Fair Value at December 31, 2023 Fair Value at December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Money market funds $ 0.6 $ — $ — $ 0.6 $ 0.5 $ — $ — $ 0.5 Mutual funds 7.2 — — 7.2 7.0 — — 7.0 Total assets $ 7.8 $ — $ — $ 7.8 $ 7.5 $ — $ — $ 7.5

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2023
Gains or Losses Recognized in AOCI for the Cash Flow Hedges	The following tables provide information on gains recognized in AOCL for the cash flow hedges for the periods indicated: Years ended December 31, 2023 2022 2021 $ in millions (net of tax) Interest Rate Interest Rate Interest Rate Beginning accumulated derivative gain in AOCL $ 12.0 $ 12.8 $ 13.6 Net gains reclassified to earnings: Interest expense (0.8) (0.8) (0.8) Ending accumulated derivative gain in AOCL $ 11.2 $ 12.0 $ 12.8 Portion expected to be reclassified to earnings in the next twelve months $ (0.8)

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Instrument [Line Items]
Long-term Debt	$ in millions Interest Rate Maturity December 31, 2023 December 31, 2022 AES Ohio debt First Mortgage Bonds 3.95% 2049 $ 425.0 $ 425.0 First Mortgage Bonds 3.20% 2040 140.0 140.0 First Mortgage Bonds 5.70% 2033 107.5 — First Mortgage Bonds 5.19% 2033 100.0 — First Mortgage Bonds 5.49% 2028 92.5 — Tax-exempt First Mortgage Bonds (a) 4.25% 2027 100.0 100.0 Tax-exempt First Mortgage Bonds (b) 4.00% 2027 40.0 40.0 U.S. Government note 4.20% 2061 16.8 17.0 Unamortized deferred financing costs (7.1) (6.9) Unamortized debt discounts (2.2) (2.4) Total long-term debt at AES Ohio 1,012.5 712.7 Senior unsecured bonds 4.125% 2025 415.0 415.0 Senior unsecured bonds 4.35% 2029 400.0 400.0 Note to DPL Capital Trust II (c) 8.125% 2031 15.6 15.6 Unamortized deferred financing costs (4.9) (6.7) Unamortized debt discounts (0.6) (0.7) Total long-term debt 1,837.6 1,535.9 Less: current portion (0.2) (0.2) Long-term debt, net of current portion $ 1,837.4 $ 1,535.7 (a) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of November 1, 2040 but are subject to a mandatory put in June 2027. (b) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of January 1, 2034 but are subject to a mandatory put in June 2027. (c) Note payable to related party. See Note 11. Related Party Transactions for more information.
Long-term Debt Maturities	At December 31, 2023, maturities of long-term debt are summarized as follows: Due during the years ending December 31, $ in millions 2024 $ 0.2 2025 415.2 2026 0.2 2027 140.2 2028 92.7 Thereafter 1,203.9 1,852.4 Unamortized debt discounts (2.8) Deferred financing costs, net (12.0) Total long-term debt $ 1,837.6
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt	$ in millions Interest Rate Maturity December 31, 2023 December 31, 2022 First Mortgage Bonds 3.95% 2049 $ 425.0 $ 425.0 First Mortgage Bonds 3.20% 2040 140.0 140.0 First Mortgage Bonds 5.70% 2033 107.5 — First Mortgage Bonds 5.19% 2033 100.0 — First Mortgage Bonds 5.49% 2028 92.5 — Tax-exempt First Mortgage Bonds (a) 4.25% 2027 100.0 100.0 Tax-exempt First Mortgage Bonds (b) 4.00% 2027 40.0 40.0 U.S. Government note 4.20% 2061 16.8 17.0 Unamortized deferred financing costs (7.1) (6.9) Unamortized debt discounts (2.2) (2.4) Total long-term debt 1,012.5 712.7 Less: current portion (0.2) (0.2) Long-term debt, net of current portion $ 1,012.3 $ 712.5 (a) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of November 1, 2040 but are subject to a mandatory put in June 2027. (b) First mortgage bonds issued to the OAQDA, to secure the loan of proceeds from tax-exempt bonds issued by the OAQDA. The bonds have a final maturity date of January 1, 2034 but are subject to a mandatory put in June 2027. Revolving Credit Agreement AES Ohio entered into a second amendment and restatement of the AES Ohio Credit Agreement on December 22, 2022 with a syndication of bank lenders. The AES Ohio Credit Agreement is an unsecured committed line of credit to be used: (i) to finance capital expenditures; (ii) to refinance certain existing indebtedness, (iii) to support working capital; and (iv) for general corporate purposes. This agreement matures on December 22, 2027, and bears interest at variable rates as described in the agreement. It includes an uncommitted $100.0 million accordion feature to provide AES Ohio with an option to request an increase in the size of the facility, subject to approval by the lenders. The AES Ohio Credit Agreement also includes two one-year extension options, allowing AES Ohio to extend the maturity date subject to approval by the lenders. At December 31, 2023 and 2022, the AES Ohio Credit Agreement had outstanding borrowings of $15.0 million and $120.0 million, respectively.
Long-term Debt Maturities	At December 31, 2023, maturities of long-term debt are summarized as follows: Due during the years ending December 31, $ in millions 2024 $ 0.2 2025 0.2 2026 0.2 2027 140.2 2028 92.7 Thereafter 788.3 1,021.8 Unamortized debt discounts (7.1) Deferred financing costs, net (2.2) Total long-term debt $ 1,012.5

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Taxes [Line Items]
Schedule of Unrecognized Tax Benefits Roll Forward	$ in millions 2023 2022 2021 Unrecognized tax benefits at January 1 $ 0.4 $ 0.4 $ 1.4 Gross decreases - prior period tax positions — — (1.0) Unrecognized tax benefits at December 31 $ 0.4 $ 0.4 $ 0.4
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2023, 2022 and 2021 are as follows: Details about AOCL Components Affected line in the Consolidated Statements of Operations Years ended December 31, $ in millions 2023 2022 2021 Gains and losses on cash flow hedges (Note 5): Interest expense, net $ (1.0) $ (1.0) $ (1.0) Income tax effect 0.2 0.2 0.2 Net of income taxes (0.8) (0.8) (0.8) Amortization of unfunded pension and other postretirement obligations (Note 8): Other expense 0.2 1.3 2.5 Income tax effect — (0.3) (0.6) Net of income taxes 0.2 1.0 1.9 Total reclassifications for the period, net of income taxes $ (0.6) $ 0.2 $ 1.1
Components of Income Tax Expense	DPL’s components of income tax expense for both continuing and discontinued operations were as follows: Years ended December 31, $ in millions 2023 2022 2021 Components of tax expense / (benefit) Federal - current $ (20.0) $ (7.6) $ (5.5) State and local - current 0.4 — — Total current (19.6) (7.6) (5.5) Federal - deferred 24.5 (2.1) 4.4 State and local - deferred 1.7 0.1 0.4 Total deferred 26.2 (2.0) 4.8 Tax expense / (benefit) $ 6.6 $ (9.6) $ (0.7)
Schedule of Effective Income Tax Rate Reconciliation	The following table summarizes a reconciliation of the U.S. statutory federal income tax rate to the effective tax rate, as a percentage of total income before taxes: Years ended December 31, 2023 2022 2021 Statutory Federal tax rate 21.0 % 21.0 % 21.0 % State taxes, net of Federal tax benefit 2.5 % (1.6) % 2.8 % AFUDC - equity (0.2) % 2.5 % 3.3 % Depreciation of flow-through differences (7.6) % 43.8 % (29.0) % Amortization of investment tax credits — % 0.1 % (0.6) % Other, net (0.1) % 1.3 % (0.8) % Effective tax rate 15.6 % 67.1 % (3.3) %
Components of Deferred Tax Assets and Liabilities	December 31, $ in millions 2023 2022 Net non-current assets / (liabilities) Depreciation / property basis $ (199.4) $ (185.5) Income taxes recoverable 9.5 9.2 Regulatory assets (39.3) (22.8) Investment tax credit — 0.1 Compensation and employee benefits (3.7) (2.8) Long-term debt 4.9 5.1 Other (a) 0.7 (2.3) Net non-current liabilities $ (227.3) $ (199.0) (a) The Other caption includes deferred tax assets of $35.9 million in 2023 and $36.6 million in 2022 related to state and local tax net operating loss carryforwards, with related valuation allowances of $35.7 million in 2023 and $36.6 million in 2022. These net operating loss carryforwards expire from 2024 to 2038.
Tax expense / (benefit) credited to Accumulated other comprehensive loss	The following table presents the tax expense / (benefit) related to pensions, postemployment benefits, cash flow hedges and financial instruments that were credited to Accumulated other comprehensive loss: Years ended December 31, $ in millions 2023 2022 2021 Tax expense / (benefit) $ (0.6) $ 0.8 $ 2.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Schedule of Unrecognized Tax Benefits Roll Forward	$ in millions 2023 2022 2021 Unrecognized tax benefits at January 1 $ 0.4 $ 0.4 $ 1.4 Gross decreases - prior period tax positions — — (1.0) Unrecognized tax benefits at December 31 $ 0.4 $ 0.4 $ 0.4
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The amounts reclassified out of Accumulated other comprehensive loss by component during the years ended December 31, 2023, 2022 and 2021 are as follows: Details about AOCL Components Affected line in the Statements of Operations Years ended December 31, $ in millions 2023 2022 2021 Amortization of unfunded pension and other postretirement obligations (Note 7): Other expense $ 0.6 $ 3.6 $ 5.0 Income tax effect (0.2) (0.9) (1.1) Total reclassifications for the period, net of income taxes $ 0.4 $ 2.7 $ 3.9
Components of Income Tax Expense	’s components of income tax expense were as follows: Years ended December 31, $ in millions 2023 2022 2021 Components of tax expense / (benefit) Federal - current $ 4.1 $ (0.8) $ 1.1 State and local - current 0.4 — 0.1 Total current 4.5 (0.8) 1.2 Federal - deferred 7.3 (2.4) 4.1 State and local - deferred 1.7 0.1 0.4 Total deferred 9.0 (2.3) 4.5 Tax expense / (benefit) $ 13.5 $ (3.1) $ 5.7
Schedule of Effective Income Tax Rate Reconciliation	Years ended December 31, 2023 2022 2021 Statutory Federal tax rate 21.0 % 21.0 % 21.0 % State taxes, net of Federal tax benefit 1.4 % 1.4 % 1.1 % AFUDC - Equity (0.1) % (2.2) % 1.3 % Amortization of investment tax credits — % (0.1) % (0.2) % Depreciation of flow-through differences (4.3) % (39.4) % (11.7) % Change in tax reserves — % — % (0.1) % Other - net — % (0.3) % (0.6) % Effective tax rate 18.0 % (19.6) % 10.8 %
Components of Deferred Tax Assets and Liabilities	December 31, $ in millions 2023 2022 Net non-current assets / (liabilities) Depreciation / property basis $ (195.3) $ (181.3) Income taxes recoverable 9.5 9.2 Regulatory assets (39.3) (22.8) Investment tax credit — 0.1 Compensation and employee benefits (4.1) (3.1) Operating loss carryforwards 21.0 2.4 Other 2.1 0.6 Net non-current liabilities $ (206.1) $ (194.9)
Tax expense / (benefit) credited to Accumulated other comprehensive loss	Years ended December 31, $ in millions 2023 2022 2021 Tax expense / (benefit) $ (0.3) $ 1.5 $ 2.9

Benefit Plans (Tables)

Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Defined Benefit Plan, Plan Assets, Category	The fair values of our Pension Plans' assets at December 31, 2023 by asset category are as follows: $ in millions Market Value at December 31, 2023 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 84.5 $ — $ 84.5 $ — Debt securities (b) 121.1 — 121.1 — Government debt securities (c) 61.0 — 61.0 — Total common collective trusts 266.6 — 266.6 — Cash and cash equivalents (d) 1.8 1.8 — — Total pension plan assets $ 268.4 $ 1.8 $ 266.6 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost. The fair values of our pension plan assets at December 31, 2022 by asset category are as follows: $ in millions Market Value at December 31, 2022 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 88.5 $ — $ 88.5 $ — Debt securities (b) 125.7 — 125.7 — Government debt securities (c) 58.3 — 58.3 — Total common collective trusts 272.5 — 272.5 — Cash and cash equivalents (d) 1.9 1.9 — — Total pension plan assets $ 274.4 $ 1.9 $ 272.5 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost.
Pension And Postretirement Benefit Plans' Obligations And Assets	The following tables set forth the changes in the Pension Plans' obligations and assets recorded on the Consolidated Balance Sheets at December 31, 2023 and 2022. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $0.9 million, $1.7 million and $1.7 million of costs billed to the Service Company for the years ended December 31, 2023, 2022 and 2021, respectively. $ in millions Years ended December 31, Change in benefit obligation 2023 2022 Benefit obligation at January 1 $ 309.0 $ 416.2 Service cost 3.0 4.9 Interest cost 15.8 9.6 Plan amendments 1.4 — Actuarial loss / (gain) 9.6 (98.0) Benefits paid (40.2) (23.7) Benefit obligation at December 31 298.6 309.0 Change in plan assets Fair value of plan assets at January 1 274.4 363.5 Actual return / (loss) on plan assets 26.5 (73.1) Employer contributions 7.7 7.7 Benefits paid (40.2) (23.7) Fair value of plan assets at December 31 268.4 274.4 Unfunded status of plan $ (30.2) $ (34.6) December 31, Amounts recognized in the Consolidated Balance Sheets 2023 2022 Current liabilities $ (0.2) $ (0.2) Non-current liabilities (30.0) (34.4) Net liability at end of year $ (30.2) $ (34.6) Amounts recognized in Accumulated other comprehensive loss , Regulatory assets, non-current , pre-tax Components: Prior service cost $ 7.7 $ 7.3 Net actuarial loss 78.7 78.6 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 86.4 $ 85.9 Recorded in: Regulatory asset, non-current $ 60.7 $ 62.0 Accumulated other comprehensive loss 25.7 23.9 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 86.4 $ 85.9
Schedule of Net Periodic Benefit Cost / (Income)	The net periodic benefit cost of the Pension Plans was: Years ended December 31, $ in millions 2023 2022 2021 Service cost $ 3.0 $ 4.9 $ 4.5 Interest cost 15.8 9.6 8.2 Expected return on assets (17.6) (15.8) (15.0) Amortization of unrecognized: Actuarial loss 0.6 5.5 9.0 Prior service cost 1.0 1.1 0.9 Net periodic benefit cost $ 2.8 $ 5.3 $ 7.6 Rates relevant to each year's expense calculations Discount rate 5.41 % 2.83 % 2.44 % Expected return on plan assets 5.40 % 4.60 % 4.55 %
Schedule of Allocation of Plan Assets	The following table summarizes our target pension plan allocation: Long-Term Percentage of plan assets as of December 31, Asset category 2023 2022 Equity Securities 32% 32% 32% Debt Securities 68% 67% 67% Cash and Cash Equivalents —% 1% 1%
Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities	The following table presents other changes in Pension Plan assets and benefit obligations recognized in Accumulated other comprehensive loss , Regulatory assets, non-current and Regulatory liabilities, non-current : Years ended December 31, $ in millions 2023 2022 2021 Net actuarial loss / (gain) $ 0.7 $ (9.1) $ (21.7) Plan amendments 1.4 — 2.3 Reversal of amortization item: Net actuarial loss (0.6) (5.5) (9.0) Prior service cost (1.0) (1.1) (0.9) Total recognized in Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ 0.5 $ (15.7) $ (29.3) Total recognized in net periodic benefit cost and Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ 3.3 $ (10.4) $ (21.7)
Weighted Average Assumptions Used to Determine Benefit Obligations	The weighted average assumptions used to determine benefit obligations were: Benefit Obligation Assumptions Pension 2023 2022 2021 Discount rate for obligations 5.14% 5.41% 2.83% Rate of compensation increases 3.21% 3.21% 3.21%
Estimated Future Benefit Payments and Medicare Part D Reimbursements	Benefit payments, which reflect future service, are expected to be paid as follows: Estimated future benefit payments $ in millions due within the following years: Pension 2024 $ 22.4 2025 22.1 2026 22.1 2027 21.9 2028 21.8 2029 - 2033 106.7
Schedule of Unrecognized Tax Benefits Roll Forward	$ in millions 2023 2022 2021 Unrecognized tax benefits at January 1 $ 0.4 $ 0.4 $ 1.4 Gross decreases - prior period tax positions — — (1.0) Unrecognized tax benefits at December 31 $ 0.4 $ 0.4 $ 0.4
Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis	The following table presents the carrying amount, fair value, and fair value hierarchy of our financial liabilities that are not measured at fair value in the Consolidated Balance Sheets as of the periods indicated, but for which fair value is disclosed: Carrying Amount Fair Value at December 31, 2023 Carrying Amount Fair Value at December 31, 2022 $ in millions Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Long-term debt $ 1,837.6 $ — $ 1,706.2 $ 16.8 $ 1,723.0 $ 1,535.9 $ — $ 1,376.4 $ 17.0 $ 1,393.4
Fair Value, Assets Measured on Recurring Basis	The fair value of assets at December 31, 2023 and 2022 and the respective category within the fair value hierarchy for DPL was determined as follows: $ in millions Fair Value at December 31, 2023 Fair Value at December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Master trust assets Money market funds $ 0.6 $ — $ — $ 0.6 $ 0.5 $ — $ — $ 0.5 Mutual funds 7.2 — — 7.2 7.0 — — 7.0 Total assets $ 7.8 $ — $ — $ 7.8 $ 7.5 $ — $ — $ 7.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Schedule of Net Periodic Benefit Cost / (Income)	Years ended December 31, $ in millions 2023 2022 2021 Service cost $ 3.0 $ 4.9 $ 4.5 Interest cost 15.8 9.6 8.2 Expected return on assets (17.6) (15.8) (15.0) Amortization of unrecognized: Actuarial loss 1.1 7.7 11.4 Prior service cost 1.1 1.2 1.1 Net periodic benefit cost $ 3.4 $ 7.6 $ 10.2 Rates relevant to each year's expense calculations Discount rate 5.41 % 2.83 % 2.44 % Expected return on plan assets 5.40 % 4.60 % 4.55 %
Schedule of Allocation of Plan Assets	The following table summarizes our target pension plan allocation: Long-Term Percentage of plan assets as of December 31, Asset category 2023 2022 Equity Securities 32% 32% 32% Debt Securities 68% 67% 67% Cash and Cash Equivalents —% 1% 1%
Weighted Average Assumptions Used to Determine Benefit Obligations	The weighted average assumptions used to determine benefit obligations were: Benefit Obligation Assumptions Pension 2023 2022 2021 Discount rate for obligations 5.14% 5.41% 2.83% Rate of compensation increases 3.21% 3.21% 3.21%
Estimated Future Benefit Payments and Medicare Part D Reimbursements	Benefit payments, which reflect future service, are expected to be paid as follows: Estimated future benefit payments $ in millions due within the following years: Pension 2024 $ 22.4 2025 22.1 2026 22.1 2027 21.9 2028 21.8 2029 - 2033 106.7
Schedule of Unrecognized Tax Benefits Roll Forward	$ in millions 2023 2022 2021 Unrecognized tax benefits at January 1 $ 0.4 $ 0.4 $ 1.4 Gross decreases - prior period tax positions — — (1.0) Unrecognized tax benefits at December 31 $ 0.4 $ 0.4 $ 0.4
Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis	The following table presents the carrying amount, fair value, and fair value hierarchy of our financial liabilities that are not measured at fair value in the Balance Sheets as of the periods indicated, but for which fair value is disclosed: Carrying Amount Fair Value at December 31, 2023 Carrying Amount Fair Value at December 31, 2022 $ in millions Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Long-term debt $ 1,012.5 $ — $ 909.9 $ 16.8 $ 926.7 $ 712.7 $ — $ 610.9 $ 17.0 $ 627.9
Fair Value, Assets Measured on Recurring Basis	The fair value of assets at December 31, 2023 and 2022 and the respective category within the fair value hierarchy for AES Ohio was determined as follows: $ in millions Fair Value at December 31, 2023 Fair Value at December 31, 2022 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Money market funds $ 0.6 $ — $ — $ 0.6 $ 0.5 $ — $ — $ 0.5 Mutual funds 7.2 — — 7.2 7.0 — — 7.0 Total assets $ 7.8 $ — $ — $ 7.8 $ 7.5 $ — $ — $ 7.5
Pension [Member]
Pension And Postretirement Benefit Plans' Obligations And Assets	The following tables set forth the changes in the Pension Plans' obligations and assets recorded on the Consolidated Balance Sheets at December 31, 2023 and 2022. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $0.9 million, $1.7 million and $1.7 million of costs billed to the Service Company for the years ended December 31, 2023, 2022 and 2021, respectively. $ in millions Years ended December 31, Change in benefit obligation 2023 2022 Benefit obligation at January 1 $ 309.0 $ 416.2 Service cost 3.0 4.9 Interest cost 15.8 9.6 Plan amendments 1.4 — Actuarial loss / (gain) 9.6 (98.0) Benefits paid (40.2) (23.7) Benefit obligation at December 31 298.6 309.0 Change in plan assets Fair value of plan assets at January 1 274.4 363.5 Actual return / (loss) on plan assets 26.5 (73.1) Employer contributions 7.7 7.7 Benefits paid (40.2) (23.7) Fair value of plan assets at December 31 268.4 274.4 Unfunded status of plan $ (30.2) $ (34.6) December 31, Amounts recognized in the Consolidated Balance Sheets 2023 2022 Current liabilities $ (0.2) $ (0.2) Non-current liabilities (30.0) (34.4) Net liability at end of year $ (30.2) $ (34.6) Amounts recognized in Accumulated other comprehensive loss , Regulatory assets, non-current , pre-tax Components: Prior service cost $ 7.7 $ 7.3 Net actuarial loss 78.7 78.6 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 86.4 $ 85.9 Recorded in: Regulatory asset, non-current $ 60.7 $ 62.0 Accumulated other comprehensive loss 25.7 23.9 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 86.4 $ 85.9
Fair Value Measurements for Plan Assets	The fair values of our Pension Plans' assets at December 31, 2023 by asset category are as follows: $ in millions Market Value at December 31, 2023 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 84.5 $ — $ 84.5 $ — Debt securities (b) 121.1 — 121.1 — Government debt securities (c) 61.0 — 61.0 — Total common collective trusts 266.6 — 266.6 — Cash and cash equivalents (d) 1.8 1.8 — — Total pension plan assets $ 268.4 $ 1.8 $ 266.6 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost. The fair values of our Pension Plans' assets at December 31, 2022 by asset category are as follows: $ in millions Market Value at December 31, 2022 Quoted prices Significant Significant Asset category (Level 1) (Level 2) (Level 3) Common collective trusts Equities (a) $ 88.5 $ — $ 88.5 $ — Debt securities (b) 125.7 — 125.7 — Government debt securities (c) 58.3 — 58.3 — Total common collective trusts 272.5 — 272.5 — Cash and cash equivalents (d) 1.9 1.9 — — Total pension plan assets $ 274.4 $ 1.9 $ 272.5 $ — (a) This category represents investments that invest in equity securities of U.S. companies of any market capitalization and other investments (i.e.: futures, swaps, currency forwards) of foreign, emerging markets and seeks to provide long-term total return, which includes capital appreciation and income. The funds are valued using the net asset value method. (b) This category represents investments that invest in high quality issues within the U.S. corporate bond markets and global high yield bonds and emerging markets debt denominated in local currency. The funds seek to provide current income and long-term capital preservation along with access to higher yielding, relatively liquid fixed income securities. The funds are valued using the net asset value method. (c) This category represents investments that invest in U.S. treasury strips, U.S. government agency obligations, and U.S. treasury obligations. The funds seek investment returns over the long term and are valued using the net asset value method. (d) This category represents an investment that seeks to maximize current income on cash reserves to the extent consistent with principal preservation and maintenance of liquidity from a portfolio of obligations of the U.S. Government, its agencies or municipalities, and related money market instruments. Principal preservation is a primary objective. The fund is valued at cost.
Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Pension And Postretirement Benefit Plans' Obligations And Assets	The following tables set forth the changes in the Pension Plans' obligations and assets recorded on the Balance Sheets at December 31, 2023 and 2022. The amounts presented in the following tables for pension obligations include the collective bargaining plan formula, traditional management plan formula and cash balance plan formula and the SERP in the aggregate and have not been adjusted for $0.9 million, $1.7 million and $1.7 million of costs billed to the Service Company for the years ended December 31, 2023, 2022 and 2021, respectively, or $0.2 million, $0.9 million and $1.9 million of costs billed to AES Ohio Generation for the years ended December 31, 2023, 2022 and 2021, respectively. $ in millions Years ended December 31, Change in benefit obligation 2023 2022 Benefit obligation at January 1 $ 309.0 $ 416.2 Service cost 3.0 4.9 Interest cost 15.8 9.6 Plan amendments 1.4 — Actuarial loss / (gain) 9.6 (98.0) Benefits paid (40.2) (23.7) Benefit obligation at December 31 298.6 309.0 Change in plan assets Fair value of plan assets at January 1 274.4 363.5 Actual return / (loss) on plan assets 26.5 (73.1) Employer contributions 7.7 7.7 Benefits paid (40.2) (23.7) Fair value of plan assets at December 31 268.4 274.4 Unfunded status of plan $ (30.2) $ (34.6) December 31, Amounts recognized in the Balance Sheets 2023 2022 Current liabilities $ (0.2) $ (0.2) Non-current liabilities (30.0) (34.4) Net liability at end of year $ (30.2) $ (34.6) Amounts recognized in Accumulated other comprehensive loss , Regulatory assets, non-current , pre-tax Components: Prior service cost $ 7.6 $ 7.3 Net actuarial loss 102.3 102.7 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 109.9 $ 110.0 Recorded in: Regulatory assets, non-current $ 60.7 $ 62.0 Accumulated other comprehensive loss 49.2 48.0 Accumulated other comprehensive loss, Regulatory assets, pre-tax $ 109.9 $ 110.0
Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities	Years ended December 31, $ in millions 2023 2022 2021 Net actuarial loss / (gain) $ 0.7 $ (9.1) $ (21.7) Plan amendments 1.4 — 2.3 Reversal of amortization item: Net actuarial loss (1.1) (7.7) (11.4) Prior service cost (1.1) (1.2) (1.1) Total recognized in Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ (0.1) $ (18.0) $ (31.9) Total recognized in net periodic benefit cost and Accumulated other comprehensive loss, Regulatory assets and Regulatory liabilities $ 3.3 $ (10.4) $ (21.7)

Contractual Obligations, Comm_2

Contractual Obligations, Commercial Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Schedule Of Contractual Obligations And Commercial Commitments	We enter into various contractual obligations and other commercial commitments that may affect the liquidity of our operations. At December 31, 2023, these include: Payments due in: $ in millions Total Less than 2 - 3 4 - 5 More than Electricity purchase commitments $ 569.3 $ 365.8 $ 203.5 $ — $ — Purchase orders and other contractual obligations $ 421.1 $ 318.3 $ 83.4 $ 19.4 $ —
THE DAYTON POWER AND LIGHT COMPANY [Member]
Schedule Of Contractual Obligations And Commercial Commitments	We enter into various contractual obligations and other commercial commitments that may affect the liquidity of our operations. At December 31, 2023, these include: Payments due in: $ in millions Total Less than 2 - 3 4 - 5 More than Electricity purchase commitments $ 569.3 $ 365.8 $ 203.5 $ — $ — Purchase orders and other contractual obligations $ 419.4 $ 316.6 $ 83.4 $ 19.4 $ —

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2023
Entity Information [Line Items]
Schedule of Related Party Transactions [Table Text Block]	The following table provides a summary of our related party transactions: Years ended December 31, $ in millions 2023 2022 2021 The following transactions are included in Operation and Maintenance on the Consolidated Statements of Operations: Net charges from the Service Company $ 48.3 $ 39.9 $ 34.9 Services provided by AES and other AES affiliates $ 16.8 $ 16.5 $ 15.5 Services provided by other related parties $ 1.7 $ 2.5 $ 1.6 Balances with related parties (included in Accounts Receivable, net and A ccounts Payable ): At December 31, 2023 At December 31, 2022 Net payable to the Service Company $ (3.9) $ (9.8) Net receivable from AES and other AES affiliates $ — $ 0.3
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Schedule of Related Party Transactions [Table Text Block]	The following table provides a summary of our related party transactions: Years ended December 31, $ in millions 2023 2022 2021 The following transactions are included in Operation and Maintenance on the Statements of Operations: Net charges from the Service Company $ 47.5 $ 39.2 $ 33.9 Services provided by AES and other AES affiliates $ 32.2 $ 28.1 $ 21.9 Services provided by other related parties $ 1.7 $ 2.5 $ 1.6 Balances with related parties (include in Accounts Receivable, net and Accounts Payable ): At December 31, 2023 At December 31, 2022 Net payable to the Service Company $ (3.9) $ (9.8) Net receivable from AES and other AES affiliates $ 2.4 $ 1.2

Business Segments Business Segm

Business Segments Business Segments (Tables)	12 Months Ended
	Dec. 31, 2023
Segment Reporting Information [Line Items]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	The following tables present financial information for DPL’s reportable business segment: $ in millions Utility Other Adjustments and Eliminations DPL Consolidated Year ended December 31, 2023 Revenue from external customers $ 851.3 $ 9.7 $ — $ 861.0 Intersegment revenue 0.7 4.4 (5.1) — Total revenue $ 852.0 $ 14.1 $ (5.1) $ 861.0 Depreciation and amortization $ 80.7 $ 1.4 $ — $ 82.1 Interest expense $ 25.8 $ 37.8 $ — $ 63.6 Income / (loss) from continuing operations before income tax $ 74.9 $ (32.6) $ — $ 42.3 Cash capital expenditures $ 384.3 $ 3.6 $ — $ 387.9 $ in millions Utility Other Adjustments and Eliminations DPL Consolidated Year ended December 31, 2022 Revenue from external customer $ 859.3 $ 9.7 $ — $ 869.0 Intersegment revenue 0.8 3.6 (4.4) — Total revenue $ 860.1 $ 13.3 $ (4.4) $ 869.0 Depreciation and amortization $ 78.7 $ 1.3 $ — $ 80.0 Interest expense $ 28.8 $ 39.0 $ — $ 67.8 Income / (loss) from continuing operations before income tax $ 15.8 $ (30.1) $ — $ (14.3) Cash capital expenditures $ 283.7 $ 3.6 $ — $ 287.3 $ in millions Utility Other Adjustments and Eliminations DPL Consolidated Year ended December 31, 2021 Revenue from external customer $ 663.0 $ 9.7 $ — $ 672.7 Intersegment revenue 0.7 3.5 (4.2) — Total revenue $ 663.7 $ 13.2 $ (4.2) $ 672.7 Depreciation and amortization $ 74.6 $ 1.5 $ — $ 76.1 Interest expense $ 24.2 $ 38.7 $ — $ 62.9 Income / (loss) from continuing operations before income tax $ 52.8 $ (30.4) $ — $ 22.4 Cash capital expenditures $ 189.3 $ 2.0 $ — $ 191.3 Total Assets December 31, 2023 December 31, 2022 December 31, 2021 Utility $ 2,871.0 $ 2,405.9 $ 2,162.6 All Other (a) 35.2 16.5 9.2 DPL Consolidated $ 2,906.2 $ 2,422.4 $ 2,171.8 (a) "All Other" includes Eliminations for all periods presented.

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2023
Disaggregation of Revenue [Table Text Block]	DPL's revenue from contracts with customers was $861.6 million, $861.4 million and $667.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. The following table presents our revenue from contracts with customers and other revenue by segment for the years ended December 31, 2023, 2022 and 2021: $ in millions Utility Other Adjustments and Eliminations Total Year ended December 31, 2023 Retail revenue Retail revenue from contracts with customers Residential revenue $ 478.9 $ — $ — $ 478.9 Commercial revenue 162.1 — — 162.1 Industrial revenue 66.6 — — 66.6 Governmental revenue 24.3 — — 24.3 Other (a) 13.0 — — 13.0 Total retail revenue from contracts with customers 744.9 — — 744.9 Wholesale revenue Wholesale revenue from contracts with customers 15.8 — (0.7) 15.1 RTO ancillary revenue 88.4 0.1 — 88.5 Capacity revenue 3.5 — — 3.5 Miscellaneous revenue Miscellaneous revenue from contracts with customers (b) — 9.6 — 9.6 Miscellaneous revenue (0.6) 4.4 (4.4) (0.6) Total revenue $ 852.0 $ 14.1 $ (5.1) $ 861.0 $ in millions Utility Other Adjustments and Eliminations Total Year ended December 31, 2022 Retail revenue Retail revenue from contracts with customers Residential revenue $ 467.3 $ — $ — $ 467.3 Commercial revenue 166.0 — — 166.0 Industrial revenue 74.3 — — 74.3 Governmental revenue 24.1 — — 24.1 Other (a) 11.9 — — 11.9 Total retail revenue from contracts with customers 743.6 — — 743.6 Wholesale revenue Wholesale revenue from contracts with customers 41.0 — (0.8) 40.2 RTO ancillary revenue 63.6 0.1 — 63.7 Capacity revenue 4.3 — — 4.3 Miscellaneous revenue Miscellaneous revenue from contracts with customers (b) — 9.6 — 9.6 Miscellaneous revenue 7.6 3.6 (3.6) 7.6 Total revenue $ 860.1 $ 13.3 $ (4.4) $ 869.0 $ in millions Utility Other Adjustments and Eliminations Total Year ended December 31, 2021 Retail revenue Retail revenue from contracts with customers Residential revenue $ 364.9 $ — $ — $ 364.9 Commercial revenue 122.6 — — 122.6 Industrial revenue 57.5 — — 57.5 Governmental revenue 26.1 — — 26.1 Other (a) 12.2 — — 12.2 Total retail revenue from contracts with customers 583.3 — — 583.3 Wholesale revenue Wholesale revenue from contracts with customers 19.5 — (0.7) 18.8 RTO ancillary revenue 49.9 0.1 — 50.0 Capacity revenue 5.9 — — 5.9 Miscellaneous revenue Miscellaneous revenue from contracts with customers (b) — 9.6 — 9.6 Miscellaneous revenue 5.1 3.5 (3.5) 5.1 Total revenue $ 663.7 $ 13.2 $ (4.2) $ 672.7 (a) "Other" primarily includes operation and maintenance service revenue, billing service fees from CRES providers and other miscellaneous retail revenue from contracts with customers. (b) Miscellaneous revenue from contracts with customers primarily includes revenue for various services provided by Miami Valley Lighting.
THE DAYTON POWER AND LIGHT COMPANY [Member]
Disaggregation of Revenue [Table Text Block]	's revenue from contracts with customers was $852.6 million, $852.5 million and $658.6 million for the years ended December 31, 2023, 2022 and 2021, respectively. The following table presents our revenue from contracts with customers and other revenue for the years ended December 31, 2023, 2022 and 2021: Years ended December 31, $ in millions 2023 2022 2021 Retail revenue Retail revenue from contracts with customers Residential revenue $ 478.9 $ 467.3 $ 364.9 Commercial revenue 162.1 166.0 122.6 Industrial revenue 66.6 74.3 57.5 Governmental revenue 24.3 24.1 26.1 Other (a) 13.0 11.9 12.2 Total retail revenue from contracts with customers 744.9 743.6 583.3 Wholesale revenue Wholesale revenue from contracts with customers 15.8 41.0 19.5 RTO ancillary revenue 88.4 63.6 49.9 Capacity revenue 3.5 4.3 5.9 Miscellaneous revenue (0.6) 7.6 5.1 Total revenue $ 852.0 $ 860.1 $ 663.7 (a)

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2023
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Summary of Balance Sheet and Profit and Loss Information for Discontinued Operations	The following table summarizes the revenue, operating costs, other expenses and income tax of discontinued operations for the period indicated: $ in millions 2021 Revenue $ 1.4 Operating costs and other expenses (2.4) Loss from discontinued operations (1.0) Income tax benefit from discontinued operations (0.2) Net loss from discontinued operations $ (0.8)

Overview and Summary of Signi_4

Overview and Summary of Significant Accounting Policies (Accounting for Taxes Collected from Customers and Remitted to Governmental Authorities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Excise Taxes Collected	$ 46.6	$ 49.2	$ 48.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
Excise Taxes Collected	$ 46.6	$ 49.2	$ 48.7

Overview and Summary of Signi_5

Overview and Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) mi² customer	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Significant Accounting Policies [Line Items]
Other Investments	$ 0.1	$ 0.2
Cash and Cash Equivalents, at Carrying Value	41	30.5
Restricted Cash and Cash Equivalents, Current	0.1	0.1
Capitalized Software, estimated amortization expense for year after next	$ 6.3
Service area, square miles | mi²	6,000
Capitalized interest for unregulated generation property	$ 6.5	$ 1.3	$ 1.6
Straight-line depreciation average annual composite basis (percent)	3.20%	3.30%	3.70%
Depreciation and amortization	$ 82.1	$ 80	$ 76.1
Insurance and claims costs	1.8	1.6
Insurance costs below coverage thresholds of third-party providers	8	7.8
Capitalized Computer Software, Amortization	4.1	3.3	3.2
Capitalized Software, estimated amortization over remaining useful life	28.7
Capitalized Software, estimated amortization expense for next twelve months	6.3
Capitalized Software, estimated amortization expense for three years in the future	5.9
Capitalized Software, estimated amortization expense for four years in the future	5.3
Capitalized Software, estimated amortization expense for five years in the future	4.9
Restricted Cash and Cash Equivalents	41.1	30.6	26.7	$ 25.5
Carrying Value	2,221	1,885
Other Assets, Noncurrent	52.4	40.3
Customer receivables	71	61.3
Unbilled revenue	19.4	24
Accounts Receivable, Allowance for Credit Loss	(0.9)	(0.5)
Accounts receivable, net	92.5	91.9
Accounts Receivable, Allowance for Credit Loss, Current	0.9	0.5	0.3
Accounts Receivable, Credit Loss Expense (Reversal)	5.4	2.5
Accounts Receivable, Allowance for Credit Loss, Writeoff	(6)	(4.1)
Accounts Receivable, Allowance for Credit Loss, Recovery	1	1.8
Other income	(56.8)	(63.6)	(62.9)
Income Tax Expense (Benefit)	6.6	(9.6)	(0.5)
Interest expense	63.6	67.8	62.9
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	(0.8)	(0.8)	(0.8)
Accumulated other comprehensive income/(loss)	(4.6)	(2.4)	(4.8)
Other comprehensive income before reclassifications	(1.6)	2.2
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	0.6	(0.2)
Other Comprehensive Income (Loss), Net of Tax	(2.2)	2.4	7.5
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	(0.8)	(0.8)	(0.8)
Other Comprehensive Income (Loss), Defined Benefit Plan, Transition Asset (Obligation), Reclassification Adjustment from AOCI, after Tax	(0.2)	(1)	(1.9)
Allowance for Funds Used During Construction, Equity Portion	5	5.7	2.1
Capitalized Computer Software, Gross	146.5	105
Capitalized Computer Software, Accumulated Amortization	(32.5)	(36.1)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Significant Accounting Policies [Line Items]
Accumulated other comprehensive income/(loss)	(15.8)	(14.4)	(17.6)
Other comprehensive income before reclassifications	(1.6)	2.2
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent		(1)
Other Comprehensive Income (Loss), Net of Tax	(1.4)	3.2
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Significant Accounting Policies [Line Items]
Accumulated other comprehensive income/(loss)	11.2	12	12.8
Other comprehensive income before reclassifications	0	0
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent		0.8
Other Comprehensive Income (Loss), Net of Tax	(0.8)	(0.8)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Significant Accounting Policies [Line Items]
Net income (loss)	(0.6)	0.2	1.1
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Significant Accounting Policies [Line Items]
Other income	0.2	1.3	2.5
Income Tax Expense (Benefit)	0	0.3	0.6
Net income (loss)	0.2	1	1.9
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Significant Accounting Policies [Line Items]
Income Tax Expense (Benefit)	(0.2)	(0.2)	(0.2)
Interest expense	1	1	1
Related Party
Significant Accounting Policies [Line Items]
Other	0.8	3.2
Nonrelated Party
Significant Accounting Policies [Line Items]
Other	2.2	3.9
Prepaid Implementation Costs for Software as a Service
Significant Accounting Policies [Line Items]
Other Assets, Noncurrent	14.8	12.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Cash and Cash Equivalents, at Carrying Value	15.5	19.7
Restricted Cash and Cash Equivalents, Current	0.1	0.1
Payments of Ordinary Dividends, Common Stock	83		52
Capitalized Software, estimated amortization expense for year after next	$ 5.6
Approximate number of retail customers | customer	539,000
Service area, square miles | mi²	6,000
Capitalized interest for unregulated generation property	$ 6.5	$ 1.3	$ 1.6
Straight-line depreciation average annual composite basis (percent)	2.60%	2.80%	2.80%
Depreciation and amortization	$ 80.7	$ 78.7	$ 74.6
Insurance costs below coverage thresholds of third-party providers	3.5	3.2
Capitalized Computer Software, Amortization	3.9	3.1	3
Capitalized Software, estimated amortization over remaining useful life	25.4
Capitalized Software, estimated amortization expense for next twelve months	5.6
Capitalized Software, estimated amortization expense for three years in the future	5.2
Capitalized Software, estimated amortization expense for four years in the future	4.6
Capitalized Software, estimated amortization expense for five years in the future	4.4
Restricted Cash and Cash Equivalents	15.6	19.8	14.5	$ 11.8
Carrying Value	2,195.9	1,861.5
Other Assets, Noncurrent	52.9	40.4
Customer receivables	70	60.6
Unbilled revenue	19.4	24
Accounts Receivable, Allowance for Credit Loss	(0.9)	(0.5)
Accounts receivable, net	93.1	92.3
Accounts Receivable, Allowance for Credit Loss, Current	0.9	0.5	0.3
Accounts Receivable, Credit Loss Expense (Reversal)	5.4	2.5
Accounts Receivable, Allowance for Credit Loss, Writeoff	(6)	(4.1)
Accounts Receivable, Allowance for Credit Loss, Recovery	1	1.8
Other income	(20)	(27)	(26.7)
Income Tax Expense (Benefit)	13.5	(3.1)	5.7
Interest expense	25.8	28.8	24.2
Accumulated other comprehensive income/(loss)	(27.9)	(26.8)	(31.8)
Other comprehensive income before reclassifications	(1.5)	2.3
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent		(2.7)
Other Comprehensive Income (Loss), Net of Tax	(1.1)	5	10.3
Other Comprehensive Income (Loss), Defined Benefit Plan, Transition Asset (Obligation), Reclassification Adjustment from AOCI, after Tax	(0.4)	(2.7)	(3.9)
Allowance for Funds Used During Construction, Equity Portion	5	5.7	2.1
Capitalized Computer Software, Gross	142.2	101.5
Capitalized Computer Software, Accumulated Amortization	(30.8)	(34.3)
THE DAYTON POWER AND LIGHT COMPANY [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Significant Accounting Policies [Line Items]
Net income (loss)	0.4	2.7	3.9
THE DAYTON POWER AND LIGHT COMPANY [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Significant Accounting Policies [Line Items]
Other income	0.6	3.6	5
Income Tax Expense (Benefit)	0.2	0.9	1.1
THE DAYTON POWER AND LIGHT COMPANY [Member] | Related Party
Significant Accounting Policies [Line Items]
Other	2.4	4.4
THE DAYTON POWER AND LIGHT COMPANY [Member] | Nonrelated Party
Significant Accounting Policies [Line Items]
Other	2.2	3.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Prepaid Implementation Costs for Software as a Service
Significant Accounting Policies [Line Items]
Other Assets, Noncurrent	14.8	12.5
Note to DPL Capital Trust II Maturing in 2031 - 8.125% [Member]
Significant Accounting Policies [Line Items]
Note payable to trust	15.6	15.6
Electric Generation, Transmission and Distribution Equipment [Member]
Significant Accounting Policies [Line Items]
Depreciation and amortization	78	76.7	72.9
Electric Generation, Transmission and Distribution Equipment [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Significant Accounting Policies [Line Items]
Depreciation and amortization	$ 76.8	$ 75.6	$ 71.6

Regulatory Matters (Details)

Regulatory Matters (Details) - USD ($) $ in Millions				12 Months Ended			60 Months Ended
	Jul. 01, 2025	Apr. 10, 2023	Dec. 14, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2028
Regulatory assets earning a return				$ 9.3
Regulatory Assets, Noncurrent				155.7	$ 129.8
Regulatory Assets, Current				56.6	39.2
Regulatory Assets				212.3	169
Regulatory Liability, Noncurrent				182.1	198.7
Regulatory Liability, Current				18	40.4
Regulatory Liabilities				200.1	239.1
DRO Vegetation Management Cost Baseline				20
DRO Vegetation Management Cost Deferral Cap				7.5
RSC Rider				$ 79
Return on Equity SEET Threshold				9.85%
Cash Contribution from Parent Company				$ 260		$ 150
Equity Contribution from Parent				239	0	132.5
Revenue Increase - Distribution Rate Case			$ 75.6
Return on Equity - Distribution Rate Case			9.999%
Cost of Long-term Debt - Distribution Rate Case			4.40%
Rate Base - Distribution Rate Case			$ 783.5
Capital Structure - Equity - Distribution Rate Case			53.87%
Capital Structure - Long-term Debt - Distribution Rate Case			46.13%
Maximum Regulatory compliance cost to be accrued							$ 4
Maximum CIS Replacement cost deferral				8.8
Vegetation Management and Other [Member]
Regulatory Assets, Noncurrent				$ 19.9
Undercollections to be collected [Member]
Regulatory Assets Type of Recovery				A/B
Regulatory Current Asset, End Date for Recovery				2024
Regulatory Assets, Current				$ 51.7	38.7
Amounts being recovered through base rates [Member]
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				2024
Regulatory Assets, Current				$ 1.7	0
Pension Costs [Member]
Regulatory Assets Type of Recovery				A/B
Regulatory Current Asset, End Date for Recovery				Ongoing
Regulatory Assets, Noncurrent				$ 62.6	64.2
Deferred Regulatory Compliance Costs [Member]
Regulatory Assets Type of Recovery				A
Regulatory Current Asset, End Date for Recovery				2028
Regulatory Assets, Noncurrent				$ 45	6.4
Ccem Smart Grid And Advanced Metering Infrastructure Cost [Member]
Regulatory Assets Type of Recovery				B/C
Regulatory Current Asset, End Date for Recovery				Ongoing
Regulatory Assets, Noncurrent				$ 3.2	2.3
Loss on Reacquired Debt [Member]
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				Ongoing
Regulatory Assets, Noncurrent				$ 1.1	2
Storm Costs [Member]
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				Ongoing
Regulatory Assets, Noncurrent				$ 2.2	8.7
Vegetation Management [Member]
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				2028
Regulatory Assets, Noncurrent					21.9
Decoupling Deferral and Other [Member] [Domain]
Regulatory Assets Type of Recovery				A
Regulatory Current Asset, End Date for Recovery				2028
Regulatory Assets, Noncurrent				$ 0	13.8
Uncollectible and Other [Member] [Domain]
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				2028
Regulatory Assets, Noncurrent				$ 6.3	7.5
Storm Costs
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				2028
Regulatory Assets, Noncurrent				$ 1.5	1.9
Energy Efficiency
Regulatory Assets Type of Recovery				D
Regulatory Current Asset, End Date for Recovery				Undetermined
Regulatory Assets, Noncurrent				$ 4.1	0
Transmission Formula Rate Debits
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				2025
Regulatory Assets, Noncurrent				$ 6.7	0
CIS Replacement Costs
Regulatory Assets Type of Recovery				D
Regulatory Current Asset, End Date for Recovery				Undetermined
Regulatory Assets, Noncurrent				$ 3.1	1.1
Vegetation management costs recovered in base rates
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				2024
Regulatory Assets, Current				$ 2.7	0
Rate case expenses recovered through base rates
Regulatory Assets Type of Recovery				B
Regulatory Current Asset, End Date for Recovery				2024
Regulatory Assets, Current				$ 0.5	0.5
Subsidiaries [Member]
Regulatory assets earning a return				9.3
Regulatory Assets, Noncurrent				155.7	129.8
Regulatory Assets, Current				56.6	39.2
Regulatory Assets				212.3	169
Regulatory Liability, Noncurrent				182.1	198.7
Regulatory Liability, Current				18	40.4
Regulatory Liabilities				200.1	239.1
TCJA Yearly Refund to Customers Per DRO				4
DRO Vegetation Management Cost Baseline				20
DRO Vegetation Management Cost Deferral Cap				7.5
RSC Rider				$ 79
Return on Equity SEET Threshold				9.85%
Equity Contribution from Parent				$ 260	0	$ 150
Revenue Increase - Distribution Rate Case			$ 75.6
Return on Equity - Distribution Rate Case			9.999%
Cost of Long-term Debt - Distribution Rate Case			4.40%
Rate Base - Distribution Rate Case			$ 783.5
Capital Structure - Equity - Distribution Rate Case			53.87%
Capital Structure - Long-term Debt - Distribution Rate Case			46.13%
Return on Equity - ESP 4		9.999%
Recovery - ESP 4		$ 66
Deferral of Purchased Power Costs - ESP 4				28.3
Deferral of Carrying Costs - ESP 4				10.7
Maximum CIS Replacement cost deferral				8.8
Subsidiaries [Member] | Vegetation Management and Other [Member]
Regulatory Assets, Noncurrent				$ 19.9
Subsidiaries [Member] | Undercollections to be collected [Member]
Regulatory Assets Type of Recovery				A/B
Regulatory Assets, Current				$ 51.7	38.7
Subsidiaries [Member] | Amounts being recovered through base rates [Member]
Regulatory Assets Type of Recovery				B
Regulatory Assets, Current				$ 1.7	0
Subsidiaries [Member] | Pension Costs [Member]
Regulatory Assets Type of Recovery				A/B
Regulatory Assets, Noncurrent				$ 62.6	64.2
Subsidiaries [Member] | Deferred Regulatory Compliance Costs [Member]
Regulatory Assets Type of Recovery				A
Regulatory Assets, Noncurrent				$ 45	6.4
Subsidiaries [Member] | Ccem Smart Grid And Advanced Metering Infrastructure Cost [Member]
Regulatory Assets Type of Recovery				B/C
Regulatory Assets, Noncurrent				$ 3.2	2.3
Subsidiaries [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets Type of Recovery				B
Regulatory Assets, Noncurrent				$ 1.1	2
Subsidiaries [Member] | Storm Costs [Member]
Regulatory Assets Type of Recovery				B
Regulatory Assets, Noncurrent				$ 2.2	8.7
Subsidiaries [Member] | Vegetation Management [Member]
Regulatory Assets Type of Recovery				B
Regulatory Assets, Noncurrent					21.9
Subsidiaries [Member] | Decoupling Deferral and Other [Member] [Domain]
Regulatory Assets Type of Recovery				A
Regulatory Assets, Noncurrent				$ 0	13.8
Subsidiaries [Member] | Uncollectible and Other [Member] [Domain]
Regulatory Assets Type of Recovery				B
Regulatory Assets, Noncurrent				$ 6.3	7.5
Subsidiaries [Member] | Storm Costs
Regulatory Assets Type of Recovery				B
Subsidiaries [Member] | Energy Efficiency
Regulatory Assets Type of Recovery				D
Regulatory Assets, Noncurrent				$ 4.1	0
Subsidiaries [Member] | Transmission Formula Rate Debits
Regulatory Assets Type of Recovery				B
Regulatory Assets, Noncurrent				$ 6.7	0
Subsidiaries [Member] | CIS Replacement Costs
Regulatory Assets Type of Recovery				D
Regulatory Assets, Noncurrent				$ 3.1	1.1
Subsidiaries [Member] | Vegetation management costs recovered in base rates
Regulatory Assets Type of Recovery				B
Regulatory Assets, Current				$ 2.7	0
Subsidiaries [Member] | Rate case expenses recovered through base rates
Regulatory Assets Type of Recovery				B
Regulatory Assets, Current				$ 0.5	0.5
Postretirement Benefit Costs [Member]
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Amortization Through				Ongoing
Regulatory Liability, Noncurrent				$ 2.6	3.3
Postretirement Benefit Costs [Member] | Subsidiaries [Member]
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 2.6	3.3
PJM transmission enhancement settlement repayment amount [Member]
Regulatory Current Asset, End Date for Recovery				2025
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 1.7	3.5
PJM transmission enhancement settlement repayment amount [Member] | Subsidiaries [Member]
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 1.7	3.5
Deferred Income Tax Charge [Member]
Regulatory Liability, Amortization Through				Ongoing
Regulatory Liability, Noncurrent				$ 42.6	45.2
Deferred Income Tax Charge [Member] | Subsidiaries [Member]
Regulatory Liability, Noncurrent				$ 42.6	45.2
TCJA Regulatory Liability [Member] [Domain]
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Amortization Through				Ongoing
Regulatory Liability, Noncurrent				$ 1	4.5
TCJA Regulatory Liability [Member] [Domain] | Subsidiaries [Member]
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 1	4.5
Removal Costs [Member]
Regulatory Liability, Noncurrent				134.2	136.8
Removal Costs [Member] | Subsidiaries [Member]
Regulatory Liability, Noncurrent				$ 134.2	136.8
Overcollection of costs to be refunded [Member]
Regulatory Current Asset, End Date for Recovery				2024
Regulatory Liabilities Type of Recovery				A/B
Regulatory Liability, Noncurrent				$ 14.7	27.6
Overcollection of costs to be refunded [Member] | Subsidiaries [Member]
Regulatory Liabilities Type of Recovery				A/B
Regulatory Liability, Noncurrent				$ 14.7	27.6
Transmission Formula Rate Credits
Regulatory Current Asset, End Date for Recovery				2024
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 3.3	12.8
Transmission Formula Rate Credits | Subsidiaries [Member]
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 3.3	12.8
Transmission Formula Rate Credits, Noncurrent
Regulatory Current Asset, End Date for Recovery				2024
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 0	5.4
Transmission Formula Rate Credits, Noncurrent | Subsidiaries [Member]
Regulatory Liabilities Type of Recovery				B
Regulatory Liability, Noncurrent				$ 0	$ 5.4
Forecast [Member]
TCJA Yearly Refund to Customers Per DRO				4
Estimated Smart Grid Phase 2 costs	$ 683
Forecast [Member] | Subsidiaries [Member]
TCJA Yearly Refund to Customers Per DRO				$ 4
Estimated Smart Grid Phase 2 costs	$ 683

Regulatory Matters (Details)_2

Regulatory Matters (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Regulatory Assets, Noncurrent	$ 155.7	$ 129.8
RSC Rider	79
THE DAYTON POWER AND LIGHT COMPANY [Member]
Regulatory Assets, Noncurrent	155.7	$ 129.8
RSC Rider	$ 79

Property, Plant and Equipment w

Property, Plant and Equipment with Corresponding Depreciation Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service	$ 2,521.9	$ 2,193.6
Total property, plant and equipment in service, Composite Rate	3.20%	3.30%	3.70%
Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	$ 505.3	$ 399.2
Distribution	1,860.9	1,658.9
General	19.3	20.7
Non-depreciable	99.5	79.4
Total property, plant and equipment in service	$ 2,485	$ 2,158.2
Transmission, Composite Rate	2.50%	2.40%
Distribution, Composite Rate	3.50%	3.70%
General, Composite Rate	5.90%	5.20%
Unregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Non-depreciable	$ 5.6	$ 4.8
Total property, plant and equipment in service	36.9	35.4
Other	$ 31.3	$ 30.6
Other, Composite Rate	4.10%	3.70%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service	$ 3,063.2	$ 2,752.7
Total property, plant and equipment in service, Composite Rate	2.60%	2.80%	2.80%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	$ 648	$ 545.3
Distribution	2,283.4	2,093.8
General	32.2	34.2
Non-depreciable	$ 99.6	$ 79.4
Transmission, Composite Rate	2%	2%
Distribution, Composite Rate	2.90%	3.10%
General, Composite Rate	3.50%	4%

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value and Cost of Non-Derivative Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Carrying Value [Member] | Debt [Member]
Long-term Debt	$ 1,837.6	$ 1,535.9
Carrying Value [Member] | Debt [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Long-term Debt	1,012.5	712.7
Fair Value [Member] | Money Market Funds [Member]
Total Master Trust Assets, Fair Value	0.6	0.5
Fair Value [Member] | Money Market Funds [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	$ 0.6	$ 0.5

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unrealized Gain (Loss) on Investments	$ 0.5	$ (1.5)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Investments	0.5	(1.5)
Entity Information [Line Items]
Unrealized Gain (Loss) on Investments	0.5	(1.5)
Fair Value, Inputs, Level 1 [Member]
Total Liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Total Liabilities	1,706.2	1,376.4
Fair Value, Inputs, Level 3 [Member]
Total Liabilities	16.8	17
THE DAYTON POWER AND LIGHT COMPANY [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Unrealized Gain (Loss) on Investments	0.5	(1.5)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gain (Loss) on Investments	0.5	(1.5)
Entity Information [Line Items]
Unrealized Gain (Loss) on Investments	0.5	$ (1.5)
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member]
Total Liabilities	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member]
Total Liabilities	909.9
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member]
Total Liabilities	$ 16.8

Fair Value Measurements (Fair_2

Fair Value Measurements (Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 2,221	$ 1,885
THE DAYTON POWER AND LIGHT COMPANY [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value	$ 2,195.9	$ 1,861.5

Fair Value Measurements (Fair_3

Fair Value Measurements (Fair Value of Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Inputs, Level 1 [Member]
Total Assets	$ 7.8	$ 7.5
Total Liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Assets	7.8	7.5
Debt Instrument, Fair Value Disclosure		0
Total Liabilities	0
Fair Value, Inputs, Level 2 [Member]
Total Assets	0	0
Total Liabilities	1,706.2	1,376.4
Fair Value, Inputs, Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Assets	0	0
Debt Instrument, Fair Value Disclosure		610.9
Total Liabilities	909.9
Fair Value, Inputs, Level 3 [Member]
Total Assets	0	0
Total Liabilities	16.8	17
Fair Value, Inputs, Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Assets	0	0
Debt Instrument, Fair Value Disclosure		17
Total Liabilities	16.8
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Total Master Trust Assets, Fair Value	0.6	0.5
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.6	0.5
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Total Master Trust Assets, Fair Value	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Mutual Fund | Fair Value, Inputs, Level 1 [Member]
Total Master Trust Assets, Fair Value	7.2	7
Mutual Fund | Fair Value, Inputs, Level 1 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	7.2	7
Mutual Fund | Fair Value, Inputs, Level 2 [Member]
Total Master Trust Assets, Fair Value	0	0
Mutual Fund | Fair Value, Inputs, Level 2 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Mutual Fund | Fair Value, Inputs, Level 3 [Member]
Total Master Trust Assets, Fair Value	0	0
Mutual Fund | Fair Value, Inputs, Level 3 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0	0
Carrying Value [Member] | Debt [Member]
Long-term Debt	1,837.6	1,535.9
Carrying Value [Member] | Debt [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Long-term Debt	1,012.5	712.7
Fair Value [Member]
Total Assets	7.8	7.5
Total Liabilities	1,723	1,393.4
Fair Value [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Assets	7.8	7.5
Total Liabilities	926.7
Fair Value [Member] | Money Market Funds [Member]
Total Master Trust Assets, Fair Value	0.6	0.5
Fair Value [Member] | Money Market Funds [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	0.6	0.5
Fair Value [Member] | Debt [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument, Fair Value Disclosure		627.9
Fair Value [Member] | Mutual Fund
Total Master Trust Assets, Fair Value	7.2	7
Fair Value [Member] | Mutual Fund | THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	$ 7.2	$ 7

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities (Gains or Losses Recognized in AOCI for the Cash Flow Hedges) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	$ 11.2	$ 12	$ 12.8
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax	(0.8)	(0.8)	(0.8)
Interest Rate Contract [Member]
Portion expected to be reclassified to earnings in the next twelve months	$ (0.8)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax		$ 12	$ 12.8	$ 13.6

Debt (Long-term Debt) (Details)

Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Unamortized Deferred Financing Costs	$ (4.9)	$ (6.7)
Debt Instrument, Unamortized Discount	(2.8)
Debt Instrument, Unamortized Discount (Premium), Net	(0.6)	(0.7)
Total long-term debt at subsidiary	1,012.5	712.7
Less: current portion	(0.2)	(0.2)
Long-term debt, net of current portion	1,837.4	1,535.7
Long-Term Debt, Maturity, Year Two	415.2
Long-Term Debt, Maturity, Year Three	0.2
Long-Term Debt, Maturity, Year Four	140.2
Long-Term Debt, Maturity, Year Five	92.7
Long-Term Debt, Maturity, after Year Five	1,203.9
Total Maturities Before Unamortized Adjustments	1,852.4
Unamortized Deferred Financing Costs, Consolidated	(12)
Long Term Debt Maturities Repayments Of Principal, Total	1,837.6
Current portion - long-term debt	0.2
4.35% Senior Notes due 2029 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	400	400
U.S. Government note maturing in 2061 - 4.20% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 16.8	17
Ten Year Senior Unsecured Bonds At 435 Maturing At April 15 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.35%
Ten Year Senior Unsecured Notes At725 Maturing At October152025
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.125%
Note to DPL Capital Trust II Maturing in 2031 - 8.125% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 15.6	15.6
Debt Instrument, Interest Rate, Stated Percentage	8.125%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Unamortized Deferred Financing Costs		(6.9)
Debt Instrument, Unamortized Discount	$ (7.1)	(2.4)
Debt Instrument, Unamortized Discount (Premium), Net	(2.2)	(2.4)
Less: current portion	(0.2)	(0.2)
Long-term debt, net of current portion	1,012.3	712.5
Long-Term Debt, Maturity, Year Two	0.2
Long-Term Debt, Maturity, Year Three	0.2
Long-Term Debt, Maturity, Year Four	140.2
Long-Term Debt, Maturity, Year Five	92.7
Long-Term Debt, Maturity, after Year Five	788.3
Total Maturities Before Unamortized Adjustments	1,021.8
Unamortized Deferred Financing Costs, Consolidated	(2.2)
Long Term Debt Maturities Repayments Of Principal, Total	1,012.5
Current portion - long-term debt	$ 0.2
THE DAYTON POWER AND LIGHT COMPANY [Member] | 3.20% First Mortgage Bonds due 2040 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	3.20%
THE DAYTON POWER AND LIGHT COMPANY [Member] | 4.25% Tax-exempt First Mortgage Bonds due 2027
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	4.25%
Long-term Debt, Gross	$ 100	100
THE DAYTON POWER AND LIGHT COMPANY [Member] | 4.00% Tax-exempt First Mortgage Bonds due 2027
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	4%
Long-term Debt, Gross	$ 40	40
THE DAYTON POWER AND LIGHT COMPANY [Member] | 3.2% Senior Notes due 2049
Debt Instrument [Line Items]
Long-term Debt, Gross	140	140
THE DAYTON POWER AND LIGHT COMPANY [Member] | U.S. Government note maturing in 2061 - 4.20% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 16.8	17
Debt Instrument, Interest Rate, Stated Percentage	4.20%
THE DAYTON POWER AND LIGHT COMPANY [Member] | 3.95% Senior Notes due 2049 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	3.95%
Long-term Debt, Gross	$ 425	$ 425
Debt Instrument, Interest Rate, Stated Percentage	3.95%
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.49% Tax-exempt First Mortgage Bonds due 2028
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	5.49%
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.70% Tax-exempt First Mortgage Bonds due 2033
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	5.70%
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.19% Tax-exempt First Mortgage Bonds due 2033
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	5.19%
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.70% Senior Notes due 2033
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 107.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.19% Senior Notes due 2033
Debt Instrument [Line Items]
Long-term Debt, Gross	100
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.49% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 92.5

Debt (Narrative) (Details)

Debt (Narrative) (Details)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Debt Covenant, Total Debt to Total Capitalization Ratio, Maximum	0.67
Long-term Line of Credit		$ 35,000,000
Issuance of long-term debt	$ 300,000,000	140,000,000	$ 0
Debt Covenant, Interest Coverage Ratio, Minimum	2.50
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Unamortized Deferred Financing Costs (Subsidiary)	$ (7,100,000)	(6,900,000)
Long-term Line of Credit	15,000,000	120,000,000
Issuance of long-term debt	300,000,000	140,000,000	$ 0
3.95% Senior Notes due 2049 [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 425,000,000	425,000,000
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	3.95%
Note to DPL Capital Trust II Maturing in 2031 - 8.125% [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 15,600,000	15,600,000
Revolving Credit Facility [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Covenant, Total Debt to Total Capitalization Ratio, Maximum	0.67
Uncommitted Accordion Feature	$ 100,000,000
3.2% Senior Notes due 2049 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	140,000,000	140,000,000
Five Year Senior Unsecured Notes At 4125 Maturing on July12025
Debt Instrument [Line Items]
Long-term Debt, Gross	415,000,000	415,000,000
4.25% Tax-exempt First Mortgage Bonds due 2027 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 100,000,000	100,000,000
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	4.25%
4.00% Tax-exempt First Mortgage Bonds due 2027 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 40,000,000	$ 40,000,000
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	4%
Tax-exempt First Mortgage Bonds due 2027 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Issuance of long-term debt	$ 140,000,000
Long-term Debt, Gross	$ 140,000,000
5.49% Tax-exempt First Mortgage Bonds due 2028 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	5.49%
5.70% Tax-exempt First Mortgage Bonds due 2033 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	5.70%
5.19% Tax-exempt First Mortgage Bonds due 2033 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	5.19%
First Mortgage Bonds due 2028 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Issuance of long-term debt	$ 92,500,000
First Mortgage Bonds due 2033 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Issuance of long-term debt	107,500,000
5.19% First Mortgage Bonds due 2033 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Issuance of long-term debt	$ 100,000,000
3.20% Tax-exempt First Mortgage Bonds due 2033
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	3.20%
3.20% Tax-exempt First Mortgage Bonds due 2033 | THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31)	3.20%

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 35.9	$ 36.6
Deferred tax assets related to state and local tax net operating loss carryforwards, net of related valuation allowances	35.7	36.6
Unrecognized Tax Benefits	0.4	0.4	$ 0.4	$ 1.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	0	0	(1)
Unrecognized tax benefits anticipated to result in a decrease of unrecognized tax benefits with 12 months of the balance sheet date, minimum	0
Cash Contribution from Parent Company	260		150
Payment against tax receivable balance from Parent	21		17.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits	0.4	0.4	0.4	$ 1.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	$ 0	$ 0	$ (1)

Income Taxes (Effective and Sta

Income Taxes (Effective and Statutory Rate Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Entity Information [Line Items]
Non-cash capital contribution			$ 132.5
Statutory Federal tax rate	21%	21%	21%
State taxes, net of Federal tax benefit	2.50%	(1.60%)	2.80%
Depreciation of flow-through differences	(0.20%)	2.50%	3.30%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation and Amortization, Percent	(7.60%)	43.80%	(29.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	0%	0.10%	(0.60%)
Other, net	(0.10%)	1.30%	(0.80%)
Effective tax rate	15.60%	67.10%	(3.30%)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Entity Information [Line Items]
Statutory Federal tax rate	21%	21%	21%
State taxes, net of Federal tax benefit	1.40%	1.40%	1.10%
Depreciation of flow-through differences	(0.10%)	(2.20%)	1.30%
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Percent	0%	(0.10%)	(0.20%)
Effective Income Tax Rate Reconciliation, Depreciation of flow-through years	(4.30%)	(39.40%)	(11.70%)
Effective Income Tax Rate Reconciliation, Change in Tax Reserves, Percent	0%	0%	(0.10%)
Other, net	0%	(0.30%)	(0.60%)
Effective tax rate	18%	(19.60%)	10.80%

Income Taxes (Tax or Benefit cr

Income Taxes (Tax or Benefit credited to AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Tax expense/ (benefit)	$ (0.6)	$ 0.8	$ 2.2
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Tax expense/ (benefit)	$ (0.3)	$ 1.5	$ 2.9

Income Taxes (Components of Def

Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Depreciation / property basis	$ (199.4)	$ (185.5)
Income taxes recoverable	9.5	9.2
Deferred Tax Liabilities, Regulatory Assets and Liabilities	(39.3)	(22.8)
Investment tax credit	0	0.1
Compensation and employee benefits	(3.7)	(2.8)
Long-term debt	4.9	5.1
Other	0.7	(2.3)
Deferred Income Tax Liabilities, Net	(227.3)	(199)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Depreciation / property basis	(195.3)	(181.3)
Income taxes recoverable	9.5	9.2
Deferred Tax Liabilities, Regulatory Assets and Liabilities	(39.3)	(22.8)
Investment tax credit	0	0.1
Compensation and employee benefits	4.1	3.1
Other	2.1	0.6
Deferred Income Tax Liabilities, Net	(206.1)	(194.9)
Operating Loss Carryforwards	$ 21	$ 2.4

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Contingency [Line Items]
Unrecognized tax benefits anticipated to result in a decrease of unrecognized tax benefits with 12 months of the balance sheet date, minimum	$ 0
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	0.4	$ 0.4	$ 1.4
Balance at end of year	0.4	0.4	0.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	0	0	(1)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	0.4	0.4	1.4
Balance at end of year	0.4	0.4	0.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	$ 0	$ 0	$ (1)

Income Taxes (Components of Inc

Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Federal - Current	$ (20)	$ (7.6)	$ (5.5)
State and Local - Current	0.4	0	0
Total Current	(19.6)	(7.6)	(5.5)
Federal - Deferred	24.5	(2.1)	4.4
State and Local - Deferred	1.7	0.1	0.4
Total Deferred	26.2	(2)	4.8
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	6.6	(9.6)	(0.7)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Federal - Current	4.1	(0.8)	1.1
State and Local - Current	0.4	0	0.1
Total Current	4.5	(0.8)	1.2
Federal - Deferred	7.3	(2.4)	4.1
State and Local - Deferred	1.7	0.1	0.4
Total Deferred	9	(2.3)	4.5
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	$ 13.5	$ (3.1)	$ 5.7

Benefit Plans (Weighted Average

Benefit Plans (Weighted Average Assumptions Used to Determine Benefit Obligations) (Details) - Pension [Member]	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Discount rate for obligations	5.14%	5.41%	2.83%
Rate of compensation increases	3.21%	3.21%	3.21%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for obligations	5.14%	5.41%	2.83%
Rate of compensation increases	3.21%	3.21%	3.21%

Benefit Plans (Pension and Post

Benefit Plans (Pension and Postretirement Benefit Plans' Obligations and Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	$ 9.6	$ 98
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Noncurrent liabilities	(37.7)	(41.8)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(7.2)
Noncurrent liabilities	(37.7)	(41.8)
Postretirement [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Funded (Unfunded) Status of Plan		7
Postretirement [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Funded (Unfunded) Status of Plan	7.2	7
Pension [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1	309	416.2
Service cost	3	4.9	$ 4.5
Interest cost	15.8	9.6	8.2
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	9.6	(98)
Benefit obligation at December 31	298.6	309	416.2
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1	274.4	363.5
Actual return / (loss) on plan assets	26.5	(73.1)
Contributions to plan assets	7.7	7.7
Fair value of plan assets at December 31	268.4	274.4	363.5
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(30.2)	(34.6)
Current liabilities	(0.2)	(0.2)
Noncurrent liabilities	(30)	(34.4)
Net asset / (liability) at December 31	(30.2)	(34.6)
Prior service cost	7.7	7.3
Net actuarial loss	78.7	78.6
Accumulated other comprehensive income, regulatory assets and regulatory liabilities, pre-tax	86.4	85.9
Defined Benefit Plan, Plan Assets, Benefits Paid	40.2	23.7
Defined Benefit Plan, Benefit Obligation, Benefits Paid	40.2	23.7
Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1	309	416.2
Service cost	3	4.9	4.5
Interest cost	15.8	9.6	8.2
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	9.6	(98)
Benefit obligation at December 31	298.6	309	416.2
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1	274.4	363.5
Actual return / (loss) on plan assets	26.5	(73.1)
Contributions to plan assets	7.7	7.7
Fair value of plan assets at December 31	268.4	274.4	$ 363.5
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(30.2)	(34.6)
Current liabilities	(0.2)	(0.2)
Noncurrent liabilities	(30)	(34.4)
Net asset / (liability) at December 31	(30.2)	(34.6)
Prior service cost	7.6	7.3
Net actuarial loss	102.3	102.7
Accumulated other comprehensive income, regulatory assets and regulatory liabilities, pre-tax	109.9	110
Defined Benefit Plan, Plan Assets, Benefits Paid	40.2	23.7
Defined Benefit Plan, Benefit Obligation, Benefits Paid	40.2	23.7
Regulatory Asset [Member] | Pension [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Accumulated other comprehensive income, regulatory assets and regulatory liabilities, pre-tax	60.7	62
Regulatory Asset [Member] | Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Accumulated other comprehensive income, regulatory assets and regulatory liabilities, pre-tax	60.7	62
Accumulated Other Comprehensive Income/(Loss) [Member] | Pension [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Accumulated other comprehensive income, regulatory assets and regulatory liabilities, pre-tax	25.7	23.9
Accumulated Other Comprehensive Income/(Loss) [Member] | Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Accumulated other comprehensive income, regulatory assets and regulatory liabilities, pre-tax	$ 49.2	$ 48

Benefit Plans (Narrative) (Deta

Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		$ 9,600,000	$ 98,000,000
Defined Benefit Plan, Amount Billed to Service Company		$ 900,000	1,700,000	$ 1,700,000
Defined contribution plan, maximum annual contributions per employee (percent)		85%
Employer contributions to defined contribution plan		$ 3,500,000	3,300,000	3,300,000
Accumulated benefit obligation for our defined benefit pension plans		290,000,000	301,300,000
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		(1,300,000)	2,100,000	6,400,000
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amount Billed to Service Company		$ 900,000	1,700,000	1,700,000
Defined contribution plan, maximum annual contributions per employee (percent)		85%
Employer contributions to defined contribution plan		$ 3,500,000	3,300,000	3,300,000
Accumulated benefit obligation for our defined benefit pension plans		290,000,000	301,300,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan		(7,200,000)
Defined Benefit Plan, Amount Billed to AES Ohio Generation		200,000	900,000	1,900,000
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		$ (1,200,000)	2,200,000	6,400,000
Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan employee vested percentage		100%
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent)		100%
Defined Benefit Plan [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan employee vested percentage		100%
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent)		100%
Management Employees [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan employee vested percentage		100%
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent)		100%
Cash Balance Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan employee vested percentage		100%
Defined benefit plan, percent forfeited if terminated, other than by death or disability, prior to full vesting (percent)		100%
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		$ 9,600,000	(98,000,000)
Payment for Pension Benefits		$ 7,500,000	$ 7,500,000	$ 9,800,000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		5.40%	4.60%	4.55%
Discount rate for obligations		5.14%	5.41%	2.83%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		5.41%	2.83%	2.44%
Defined Benefit Plan, Plan Assets, Amount		$ 268,400,000	$ 274,400,000	$ 363,500,000
Service cost		3,000,000	4,900,000	4,500,000
Interest cost		15,800,000	9,600,000	8,200,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan		$ (30,200,000)	(34,600,000)
Defined benefit plan, amortization period for underfunding excess		7 years
Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)		$ 9,600,000	(98,000,000)
Payment for Pension Benefits		$ 7,500,000	$ 7,500,000	$ 9,800,000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		5.40%	4.60%	4.55%
Discount rate for obligations		5.14%	5.41%	2.83%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		5.41%	2.83%	2.44%
Defined Benefit Plan, Plan Assets, Amount		$ 268,400,000	$ 274,400,000	$ 363,500,000
Service cost		3,000,000	4,900,000	4,500,000
Interest cost		15,800,000	9,600,000	$ 8,200,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan		$ (30,200,000)	(34,600,000)
Defined benefit plan, amortization period for underfunding excess		7 years
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded (Unfunded) Status of Plan			7,000,000
Postretirement [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funded (Unfunded) Status of Plan		$ 7,200,000	$ 7,000,000
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated contribution to the defined benefit plans next year		$ 200,000
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		32%
Equity Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		32%
Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.15%
Decrease in pension cost due to change in return on assets	$ (2,900,000)
Decrease in pension cost due to change in discount rate	$ (300,000)
Forecast [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.15%
Decrease in pension cost due to change in return on assets	$ (2,900,000)
Decrease in pension cost due to change in discount rate	(300,000)
Forecast [Member] | Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits	7,500,000
Service cost	5,100,000
Defined Benefit Plan, Plan Assets, Administration Expense	1,600,000
Forecast [Member] | Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits	7,500,000
Service cost	5,100,000
Defined Benefit Plan, Plan Assets, Administration Expense	$ 1,600,000
Forecast [Member] | SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	100%
Forecast [Member] | SERP [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	100%
Estimated contribution to the defined benefit plans next year	$ 200,000
Increase in Expected Rate of Return [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in Expected rate of return on plan assets	1%
Increase in Expected Rate of Return [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in Expected rate of return on plan assets	1%
Expected Increase in Discount Rate [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in discount rate for plan assets	0.25%
Expected Increase in Discount Rate [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in discount rate for plan assets	0.25%
Non-union Participant [Member] | First 1% of Eligible Compensation [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution (percent)		100%
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent)		1%
Non-union Participant [Member] | First 1% of Eligible Compensation [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution (percent)		100%
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent)		1%
Non-union Participant [Member] | Next 5% of Eligible Compensation [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution (percent)		50%
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent)		5%
Non-union Participant [Member] | Next 5% of Eligible Compensation [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution (percent)		50%
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent)		5%
Union Participant [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent)		150%
Defined contribution plan, employer matching contribution cap		$ 2,750
Union Participant [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of employees' gross pay (percent)		150%
Defined contribution plan, employer matching contribution cap		$ 2,750
Minimum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		30%
Minimum [Member] | Equity Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		30%
Minimum [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		60%
Minimum [Member] | Fixed Income Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		60%
Maximum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		40%
Maximum [Member] | Equity Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		40%
Maximum [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		70%
Maximum [Member] | Fixed Income Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		70%

Benefit Plans (Net Periodic Ben

Benefit Plans (Net Periodic Benefit Cost (Income)) (Details) - Pension [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Service cost	$ 3	$ 4.9	$ 4.5
Interest cost	15.8	9.6	8.2
Expected return on assets	(17.6)	(15.8)	(15)
Actuarial gain / (loss)	0.6	5.5	9
Prior service cost	1	1.1	0.9
Net Periodic benefit cost / (income) before adjustments	$ 2.8	$ 5.3	$ 7.6
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.41%	2.83%	2.44%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.40%	4.60%	4.55%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Service cost	$ 3	$ 4.9	$ 4.5
Interest cost	15.8	9.6	8.2
Expected return on assets	(17.6)	(15.8)	(15)
Actuarial gain / (loss)	1.1	7.7	11.4
Prior service cost	1.1	1.2	1.1
Net Periodic benefit cost / (income) before adjustments	$ 3.4	$ 7.6	$ 10.2
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.41%	2.83%	2.44%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.40%	4.60%	4.55%

Benefit Plans (Weighted Avera_2

Benefit Plans (Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost (Income)) (Details) - Pension [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.41%	2.83%	2.44%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.40%	4.60%	4.55%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	5.41%	2.83%	2.44%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.40%	4.60%	4.55%

Benefit Plans (Estimated Future

Benefit Plans (Estimated Future Benefit Payments and Medicare Part D Reimbursements) (Details) - Pension [Member] $ in Millions	Dec. 31, 2023 USD ($)
2016	$ 22.4
2017	22.1
2018	22.1
2019	21.9
2020	21.8
2021 - 2025	106.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
2016	22.4
2017	22.1
2018	22.1
2019	21.9
2020	21.8
2021 - 2025	$ 106.7

Benefit Plans (Fair Value Measu

Benefit Plans (Fair Value Measurements for Pension Plan Assets) (Details) - Pension [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	$ 268.4	$ 274.4	$ 363.5
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	1.8	1.9
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	266.6	272.5
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	0	0
Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	266.6	272.5
Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	0	0
Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	266.6	272.5
Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	0	0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	268.4	274.4	$ 363.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	1.8	1.9
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	266.6	272.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	0	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	266.6	272.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	0	0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	266.6	272.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Pension Plan Assets	0	0
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	121.1	125.7
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	121.1	125.7
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	121.1	125.7
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	121.1	125.7
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	84.5	88.5
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	84.5	88.5
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	84.5	88.5
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	84.5	88.5
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	1.8	1.9
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	1.8	1.9
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	1.8	1.9
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	1.8	1.9
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	61	58.3
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	61	58.3
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	61	58.3
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	0	0
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	61	58.3
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Equity Securities	$ 0	$ 0

Benefit Plans (Other Changes in

Benefit Plans (Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Prior service cost for the period, net of income tax benefit/(expense)	$ (0.3)	$ 0.1	$ 0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost for the period, net of income tax benefit/(expense)	(0.3)	0.1	0
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Reversal of amortization item, Net actuarial (gain) / loss	(0.6)	(5.5)	(9)
Reversal of amortization item, Prior service cost / (credit)	(1)	(1.1)	(0.9)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	0.5	(15.7)	(29.3)
Total recognized in net periodic benefit cost and Accumulated other comprehensive income, Regulatory assets and Regulatory liabilities	3.3	(10.4)	(21.7)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0.7	(9.1)	(21.7)
Prior service cost for the period, net of income tax benefit/(expense)	1.4	0	2.3
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	1.4	0
Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Reversal of amortization item, Net actuarial (gain) / loss	(1.1)	(7.7)	(11.4)
Reversal of amortization item, Prior service cost / (credit)	(1.1)	(1.2)	(1.1)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	(0.1)	(18)	(31.9)
Total recognized in net periodic benefit cost and Accumulated other comprehensive income, Regulatory assets and Regulatory liabilities	3.3	(10.4)	(21.7)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0.7	(9.1)	(21.7)
Prior service cost for the period, net of income tax benefit/(expense)	1.4	0	$ 2.3
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	$ 1.4	$ 0

Benefit Plans (Defined Benefits

Benefit Plans (Defined Benefits Plan Assets, Target Allocations) (Details)	Dec. 31, 2023	Dec. 31, 2022
Equity Securities [Member]
Target Allocation	32%
Percentage of plan assets	32%	32%
Debt Securities [Member]
Target Allocation	68%
Percentage of plan assets	67%	67%
Cash and Cash Equivalents [Member]
Target Allocation	0%
Percentage of plan assets	1%	1%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Equity Securities [Member]
Target Allocation	32%
Percentage of plan assets	32%	32%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Debt Securities [Member]
Target Allocation	68%
Percentage of plan assets	67%	67%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Cash and Cash Equivalents [Member]
Target Allocation	0%
Percentage of plan assets	1%	1%

Equity (Narrative) (Details)

Equity (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Equity Contribution from Parent	$ (239)	$ 0	$ (132.5)
Retained earnings / (deficit)	$ (2,686.9)	$ (2,722.6)
Common stock, shares authorized	1,500	1,500
Common stock, shares outstanding	1	1
Non-cash capital contribution			132.5
Cash Contribution from Parent Company	$ 260		150
Payment against tax receivable balance from Parent	21		17.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Equity Contribution from Parent	(260)	$ 0	(150)
Retained earnings / (deficit)	$ 29.3	$ (5.4)
Common stock, shares authorized	50,000,000
Common stock, shares outstanding	41,172,173	41,172,173
Dividends, Common Stock, Cash	$ 83	$ (64)	42
Payments of Ordinary Dividends, Common Stock	83		52
Other Paid-In Capital [Member]
Class of Stock [Line Items]
Equity Contribution from Parent	(239)		(132.5)
Other Paid-In Capital [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Equity Contribution from Parent	260		150
Dividends, Common Stock, Cash	56.3	49	42
Payments of Ordinary Dividends, Common Stock	$ 83	64	52
Dividends, Common Stock		$ 64	$ 42

Contractual Obligations, Comm_3

Contractual Obligations, Commercial Commitments and Contingencies (Schedule Of Contractual Obligations And Commercial Commitments) (Details) $ in Millions	Dec. 31, 2023 USD ($)
Electricity Purchase Commitments [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Electricity Purchase Commitments	$ 569.3
Electricity Purchase Agreements Less Than 1 Year	365.8
Electricity Purchase Agreements in Years 2 and 3	203.5
Electricity Purchase Agreements in Years 4 and 5	0
Electricity Purchase Agreements, After Year 5	0
Electricity Purchase Commitments [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Electricity Purchase Commitments	569.3
Electricity Purchase Agreements Less Than 1 Year	365.8
Electricity Purchase Agreements in Years 2 and 3	203.5
Electricity Purchase Agreements in Years 4 and 5	0
Electricity Purchase Agreements, After Year 5	0
Other Intangible Assets [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Total Purchase orders and other contractual obligations	421.1
Purchase orders and other contractual obligations, Less than 1 year	318.3
Purchase orders and other contractual obligations, 2 - 3 years	83.4
Purchase orders and other contractual obligations, 4 - 5 years	19.4
Purchase orders and other contractual obligations, More than 5 years	0
Other Intangible Assets [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Total Purchase orders and other contractual obligations	419.4
Purchase orders and other contractual obligations, Less than 1 year	316.6
Purchase orders and other contractual obligations, 2 - 3 years	83.4
Purchase orders and other contractual obligations, 4 - 5 years	19.4
Purchase orders and other contractual obligations, More than 5 years	$ 0

Contractual Obligations, Comm_4

Contractual Obligations, Commercial Commitments and Contingencies (Narrative) (Details) - THE DAYTON POWER AND LIGHT COMPANY [Member] $ in Millions	Dec. 31, 2023 USD ($)
Debt Obligation on 4.9% Equity Ownership [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Equity ownership interest	4.90%
Equity ownership interest aggregate cost	$ 52.5
Electric Generation Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Debt obligation	$ 1,100

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Schedule of Related Party Transactions	The following table provides a summary of our related party transactions: Years ended December 31, $ in millions 2023 2022 2021 The following transactions are included in Operation and Maintenance on the Consolidated Statements of Operations: Net charges from the Service Company $ 48.3 $ 39.9 $ 34.9 Services provided by AES and other AES affiliates $ 16.8 $ 16.5 $ 15.5 Services provided by other related parties $ 1.7 $ 2.5 $ 1.6 Balances with related parties (included in Accounts Receivable, net and A ccounts Payable ): At December 31, 2023 At December 31, 2022 Net payable to the Service Company $ (3.9) $ (9.8) Net receivable from AES and other AES affiliates $ — $ 0.3
Other Investments	$ 0.1	$ 0.2
Accounts payable	$ 163.9	129.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Schedule of Related Party Transactions	The following table provides a summary of our related party transactions: Years ended December 31, $ in millions 2023 2022 2021 The following transactions are included in Operation and Maintenance on the Statements of Operations: Net charges from the Service Company $ 47.5 $ 39.2 $ 33.9 Services provided by AES and other AES affiliates $ 32.2 $ 28.1 $ 21.9 Services provided by other related parties $ 1.7 $ 2.5 $ 1.6 Balances with related parties (include in Accounts Receivable, net and Accounts Payable ): At December 31, 2023 At December 31, 2022 Net payable to the Service Company $ (3.9) $ (9.8) Net receivable from AES and other AES affiliates $ 2.4 $ 1.2
Accounts payable	$ 163.8	129.5
Note to DPL Capital Trust II Maturing in 2031 - 8.125% [Member]
Related Party Transaction [Line Items]
Note payable to trust	15.6	15.6
Service Company
Related Party Transaction [Line Items]
Accounts payable	3.9	9.8
Service Company | THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Accounts payable	3.9	9.8
Affiliated Entity
Related Party Transaction [Line Items]
Accounts and Other Receivables, Net, Current	0	0.3
Affiliated Entity | THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Accounts and Other Receivables, Net, Current	2.4	1.2
Service Company
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	48.3	39.9	$ 34.9
Service Company | THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	47.5	39.2	33.9
Affiliated Entity
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	16.8	16.5	15.5
Affiliated Entity | THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	32.2	28.1	21.9
Other related party
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	1.7	2.5	$ 1.6
Other related party | THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 1.7	$ 2.5

Business Segments (Segment Fina

Business Segments (Segment Financial Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
External customer revenues	$ 861	$ 869	$ 672.7
Total revenue	861	869	672.7
Fuel Costs	0	0.1	0.5
Depreciation and amortization	82.1	80	76.1
Interest expense	63.6	67.8	62.9
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	42.3	(14.3)	22.4
Net loss from continuing operations	35.7	(4.7)	22.9
Discontinued operations, net of tax	0	0	(0.8)
Cash capital expenditures	387.9	287.3	191.3
Total assets (end of year)	2,906.2	2,422.4	2,171.8
Revenues	861	869	672.7
Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	0	0	0
Utility [Member]
Segment Reporting Information [Line Items]
Revenues	852	860.1	663.7
Operating Segments [Member] | Utility [Member]
Segment Reporting Information [Line Items]
External customer revenues	851.3	859.3	663
Total revenue	852	860.1	663.7
Depreciation and amortization	80.7	78.7	74.6
Interest expense	25.8	28.8	24.2
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	74.9	15.8	52.8
Cash capital expenditures	384.3	283.7	189.3
Total assets (end of year)		2,405.9	2,162.6
Operating Segments [Member] | Utility [Member] | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	0.7	0.8	0.7
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
External customer revenues	9.7	9.7	9.7
Total revenue	14.1	13.3	13.2
Depreciation and amortization	1.4	1.3	1.5
Interest expense	37.8	39	38.7
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(32.6)	(30.1)	(30.4)
Cash capital expenditures	3.6	3.6	2
Total assets (end of year)	35.2	16.5	9.2
Corporate, Non-Segment [Member] | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	4.4	3.6	3.5
Consolidation, Eliminations [Member]
Segment Reporting Information [Line Items]
External customer revenues	0	0	0
Total revenue	(5.1)	(4.4)	(4.2)
Depreciation and amortization	0	0	0
Interest expense	0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	0	0	0
Cash capital expenditures	0	0	0
Intersegment Eliminations | Intersegment revenue
Segment Reporting Information [Line Items]
Revenues	(5.1)	(4.4)	(4.2)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Segment Reporting Information [Line Items]
Fuel Costs	0	0	0.5
Depreciation and amortization	80.7	78.7	74.6
Interest expense	25.8	28.8	24.2
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	74.9	15.8	52.8
Total assets (end of year)	2,871	2,405.9
Revenues	$ 852	$ 860.1	$ 663.7

Business Segments (Narrative) (

Business Segments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2023 mi² segement customer
Segment Reporting Information [Line Items]
Service area, square miles	6,000
THE DAYTON POWER AND LIGHT COMPANY [Member]
Segment Reporting Information [Line Items]
Number of Operating Segments | segement	1
Approximate number of retail customers | customer	539,000
Service area, square miles	6,000

Revenue (Details)

Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue from Contract with Customer, Excluding Assessed Tax	$ 861.6	$ 861.4	$ 667.6
Revenues	861	869	672.7
RTO Revenue	88.5	63.7	50
RTO Capacity Revenue	3.5	4.3	5.9
Contract with Customer, Asset, before Allowance for Credit Loss	90.4	85.3
Utility [Member]
Revenues	852	860.1	663.7
RTO Revenue	88.4	63.6	49.9
RTO Capacity Revenue	3.5	4.3	5.9
Corporate and Other
Revenues	14.1	13.3	13.2
RTO Revenue	0.1	0.1	0.1
RTO Capacity Revenue	0	0	0
Adjustments and Eliminations
Revenues	(5.1)	(4.4)	(4.2)
RTO Revenue	0	0	0
RTO Capacity Revenue	0	0	0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	852.6	852.5	658.6
Revenues	852	860.1	663.7
RTO Revenue	88.4	63.6	49.9
RTO Capacity Revenue	3.5	4.3	5.9
Contract with Customer, Asset, before Allowance for Credit Loss	89.4	84.6
Wholesale Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	15.1	40.2	18.8
Wholesale Revenue [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	15.8	41	19.5
Wholesale Revenue [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Wholesale Revenue [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	(0.7)	(0.8)	(0.7)
Wholesale Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	15.8	41	19.5
Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	9.6	9.6	9.6
Other non-606 revenue	(0.6)	7.6	5.1
Other Revenues [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Other non-606 revenue	(0.6)	7.6	5.1
Other Revenues [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	9.6	9.6	9.6
Other non-606 revenue	4.4	3.6	3.5
Other Revenues [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Other non-606 revenue	(4.4)	(3.6)	(3.5)
Other Revenues [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Other non-606 revenue	(0.6)	7.6	5.1
Retail Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	744.9	743.6	583.3
Retail Revenue [Member] | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	478.9	467.3	364.9
Retail Revenue [Member] | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	162.1	166	122.6
Retail Revenue [Member] | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	66.6	74.3	57.5
Retail Revenue [Member] | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	24.3	24.1	26.1
Retail Revenue [Member] | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	13	11.9	12.2
Retail Revenue [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	744.9	743.6	583.3
Retail Revenue [Member] | Utility [Member] | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	478.9	467.3	364.9
Retail Revenue [Member] | Utility [Member] | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	162.1	166	122.6
Retail Revenue [Member] | Utility [Member] | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	66.6	74.3	57.5
Retail Revenue [Member] | Utility [Member] | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	24.3	24.1	26.1
Retail Revenue [Member] | Utility [Member] | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	13	11.9	12.2
Retail Revenue [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Corporate and Other | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Corporate and Other | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Corporate and Other | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Corporate and Other | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Corporate and Other | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Adjustments and Eliminations | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Adjustments and Eliminations | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Adjustments and Eliminations | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Adjustments and Eliminations | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | Adjustments and Eliminations | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Retail Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 744.9	$ 743.6	$ 583.3

Discontinued Operations (Detail

Discontinued Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property, Plant and Equipment, Additions	$ 0	$ 0.6	$ 3.9
Proceeds from disposal and sale of business interests	0	0.5	0
Revenues			1.4
Cost of revenues			(2.4)
Loss from discontinued operations before income tax	0	0	(1)
Income tax benefit from discontinued operations	0	0	(0.2)
Net loss from discontinued operations	$ 0	0	(0.8)
Cash Provided by (Used in) Operating Activities, Discontinued Operations			(0.8)
Cash Provided by (Used in) Investing Activities, Discontinued Operations			$ (1.6)
Conesville [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property, Plant and Equipment, Additions		$ 4

Dispositions (Details)

Dispositions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ 42.3	$ (14.3)	$ 22.4
Payments for Removal Costs	0	0.6	3.9
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ 74.9	$ 15.8	$ 52.8

Schedule II Valuation And Qua_2

Schedule II Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	$ 0.9	$ 0.5	$ 0.3
Accounts Receivable, Credit Loss Expense (Reversal)	5.4	2.5
Accounts Receivable, Allowance for Credit Loss, Writeoff	(6)	(4.1)
Accounts Receivable, Allowance for Credit Loss, Recovery	1	1.8
THE DAYTON POWER AND LIGHT COMPANY [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	0.9	0.5	0.3
Accounts Receivable, Credit Loss Expense (Reversal)	5.4	2.5
Accounts Receivable, Allowance for Credit Loss, Writeoff	(6)	(4.1)
Accounts Receivable, Allowance for Credit Loss, Recovery	1	1.8
Provision for Uncollectible Accounts [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	0.5	0.3	2.8
Additions	5.4	5	(0.4)
Deductions	2.5	2.3	2.1
Balance at End of Period	0.9	0.5	0.3
Provision for Uncollectible Accounts [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	0.5	0.3	2.8
Additions	5.4	2.5	(0.4)
Deductions	5	2.3	2.1
Balance at End of Period	0.9	0.5	0.3
Valuation Allowance For Deferred Tax Assets [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	36.6	37.1	39
Additions	0.7	0	1.5
Deductions	1.6	0.5	3.4
Balance at End of Period	$ 35.7	$ 36.6	$ 37.1