Clearway Energy (CWEN) 10-Q 2 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Jul. 31, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	NRG Yield, Inc.
Entity Central Index Key	1,567,683
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Common Class A [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		34,586,250
Common Class B [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		42,738,750
Common Class C [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		69,129,643
Common Class D [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		42,738,750

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Operating Revenues
Total operating revenues		$ 307	$ 288	[1]	$ 532	$ 509	[1]
Operating Costs and Expenses
Cost of operations		74	77	[1]	163	162	[1]
Depreciation and amortization		82	79	[1]	163	156	[1]
General and administrative		6	6	[1]	11	10	[1]
Acquisition-related transaction and integration costs		1	1	[1]	2	2	[1]
Total operating costs and expenses		163	163	[1]	339	330	[1]
Operating Income		144	125	[1]	193	179	[1]
Other Income (Expense)
Equity in earnings of unconsolidated affiliates		29	16	[1]	33	35	[1]
Other income, net		1	1	[1]	2	2	[1]
Loss on debt extinguishment		0	0	[1]	0	(2)	[1]
Interest expense		(71)	(90)	[1]	(126)	(165)	[1]
Total other expense, net		(41)	(73)	[1]	(91)	(130)	[1]
Income Before Income Taxes		103	52	[1]	102	49	[1]
Income tax expense		7	8	[1]	6	7	[1]
Net Income		96	44	[1]	96	42	[1]
Less: Pre-acquisition net income of Drop Down Assets		0	2	[1]	4	15	[1]
Net Income Excluding Pre-acquisition Net Income of Drop Down Assets		96	42	[1]	92	27	[1]
Less: Income (loss) attributable to noncontrolling interests		17	14	[1]	(3)	2	[1]
Net Income Attributable to NRG Yield, Inc.		$ 79	28	[1]	95	25	[1]
Earnings Per Share Attributable to NRG Yield, Inc. Class A and Class C Common Stockholders
Dividends Per Common Share, Cash Paid		$ 0.309
Common Class C [Member]
Other Income (Expense)
Net Income Attributable to NRG Yield, Inc.	[2]	$ 52	$ 18		$ 62	$ 16
Weighted Average Number of Shares Outstanding, Basic	[2]	67	63		66	63
Weighted Average Number of Shares Outstanding, Diluted	[2]	78	74		77	63
Earnings Per Share Attributable to NRG Yield, Inc. Class A and Class C Common Stockholders
Earnings Per Share, Basic	[2]	$ 0.77	$ 0.29		$ 0.94	$ 0.26
Earnings Per Share, Diluted	[2]	0.70	0.28		0.89	0.26
Dividends Per Common Share, Cash Paid		$ 0.309	$ 0.27		$ 0.607	$ 0.53
Common Class A [Member]
Other Income (Expense)
Net Income Attributable to NRG Yield, Inc.	[2]	$ 27	$ 10		$ 33	$ 9
Weighted Average Number of Shares Outstanding, Basic	[2]	35	35		35	35
Weighted Average Number of Shares Outstanding, Diluted	[2]	49	49		49	35
Earnings Per Share Attributable to NRG Yield, Inc. Class A and Class C Common Stockholders
Earnings Per Share, Basic	[2]	$ 0.77	$ 0.29		$ 0.94	$ 0.26
Earnings Per Share, Diluted	[2]	0.61	0.26		0.80	0.26
Dividends Per Common Share, Cash Paid		$ 0.309	$ 0.27		$ 0.607	$ 0.53
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	(a) Basic and diluted earnings per share might not recalculate due to presenting values in millions rather than whole dollars.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	[1]	Jun. 30, 2018	Jun. 30, 2017	[1]
Net income	$ 96	$ 44		$ 96	$ 42
Other Comprehensive Gain (Loss), net of tax
Unrealized gain (loss) on derivatives, net of income tax (expense) benefit of $0, $1, ($3) and $0	7	(6)		24	0
Other comprehensive gain (loss)	7	(6)		24	0
Comprehensive Income	103	38		120	42
Less: Pre-acquisition net income of Drop Down Assets	0	2		4	15
Less: Comprehensive income attributable to noncontrolling interests	21	11		10	2
Comprehensive Income Attributable to NRG Yield, Inc.	$ 82	$ 25		$ 106	$ 25
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gain/loss on derivatives, income tax expense /(benefit)	$ 0	$ 1	$ (3)	$ 0

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Jun. 30, 2018		Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 130,000,000		$ 148,000,000	[1]
Restricted cash	139,000,000		168,000,000	[1]
Accounts receivable — trade	132,000,000		95,000,000	[1]
Inventory	39,000,000		39,000,000	[1]
Notes receivable	6,000,000		13,000,000	[1]
Prepayments and other current assets	26,000,000		19,000,000	[1]
Total current assets	472,000,000		482,000,000	[1]
Property, plant and equipment, net	5,376,000,000		5,410,000,000	[1]
Other Assets
Equity investments in affiliates	1,183,000,000		1,178,000,000	[1]
Intangible assets, net	1,192,000,000		1,228,000,000	[1]
Derivative instruments	23,000,000		1,000,000	[1]
Deferred income taxes	120,000,000		128,000,000	[1]
Other non-current assets	82,000,000		62,000,000	[1]
Total other assets	2,600,000,000		2,597,000,000	[1]
Total Assets	8,448,000,000		8,489,000,000	[1]
Current Liabilities
Current portion of long-term debt	651,000,000	[2]	339,000,000	[1]
Accounts payable — trade	40,000,000		46,000,000	[1]
Accounts payable — affiliate	47,000,000		49,000,000	[1]
Derivative instruments	6,000,000		18,000,000	[1]
Accrued expenses and other current liabilities	60,000,000		88,000,000	[1]
Total current liabilities	804,000,000		540,000,000	[1]
Other Liabilities
Long-term debt	5,244,000,000		5,659,000,000	[1]
Derivative instruments	12,000,000		31,000,000	[1]
Other non-current liabilities	101,000,000		100,000,000	[1]
Total non-current liabilities	5,357,000,000		5,790,000,000	[1]
Total Liabilities	6,161,000,000		6,330,000,000	[1]
Commitments and Contingencies	0		0
Stockholders' Equity
Preferred stock, $0.01 par value; 10,000,000 shares authorized; none issued	0		0	[1]
Class A, Class B, Class C and Class D common stock, $0.01 par value; 3,000,000,000 shares authorized (Class A 500,000,000, Class B 500,000,000, Class C 1,000,000,000, Class D 1,000,000,000); 189,145,393 shares issued and outstanding (Class A 34,586,250, Class B 42,738,750, Class C 69,081,643, Class D 42,738,750) at June 30, 2018 and 184,780,837 shares issued and outstanding (Class A 34,586,250, Class B 42,738,750, Class C 64,717,087, Class D 42,738,750) at December 31, 2017	1,000,000		1,000,000	[1]
Additional paid-in capital	1,859,000,000		1,843,000,000	[1]
Retained earnings (accumulated deficit)	25,000,000		(69,000,000)	[1]
Accumulated other comprehensive loss	(17,000,000)		(28,000,000)	[1]
Noncontrolling interest	419,000,000		412,000,000	[1]
Total Stockholders' Equity	2,287,000,000		2,159,000,000	[1]
Total Liabilities and Stockholders' Equity	$ 8,448,000,000		$ 8,489,000,000	[1]
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	The 2019 Convertible Notes become due in February 2019 and are included in current portion of long-term debt on the Company's consolidated balance sheet as of June 30, 2018.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Common Stock, Par or Stated Value Per Share	$ 0.01
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Commitments and Contingencies	$ 0	$ 0
Common Class A [Member]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Issued	34,586,250	34,586,250
Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Class B [Member]
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Issued	42,738,750	42,738,750
Common Class C [Member]
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Issued	69,081,643	64,717,087
Common Class D [Member]
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Issued	42,738,750	42,738,750

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities
Net income	$ 96	$ 42	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of unconsolidated affiliates	(33)	(35)	[1]
Distributions from unconsolidated affiliates	32	29	[1]
Depreciation and amortization	163	156	[1]
Amortization of financing costs and debt discounts	13	11	[1]
Amortization of intangibles and out-of-market contracts	35	34	[1]
Adjustment for debt extinguishment	0	(2)	[1]
Changes in deferred income taxes	6	7	[1]
Derivative interest (income) expense	(32)	2	[1]
(Gain) loss on disposal of asset components	(1)	4	[1]
Changes in prepaid and accrued liabilities for tolling agreements	(62)	(64)	[1]
Changes in other working capital	(36)	(19)	[1]
Net Cash Provided by Operating Activities	181	169	[1]
Cash Flows from Investing Activities
Acquisition of businesses, net of cash acquired	11	0
Payments for the Drop Down Assets	126	131	[1]
Capital expenditures	(45)	(60)	[1]
Cash receipts from notes receivable	7	9	[1]
Return of investment from unconsolidated affiliates	18	25	[1]
Investments in unconsolidated affiliates	(16)	(33)	[1]
Payments for (Proceeds from) Other Investing Activities	(7)	0	[1]
Net Cash Used in Investing Activities	(166)	(190)	[1]
Cash Flows from Financing Activities
Net contributions from noncontrolling interests	94	15	[1]
Net distributions and return of capital to NRG prior to the acquisition of Drop Down Assets	0	(26)	[1]
Net proceeds from the issuance of common stock	75	16	[1]
Payments of dividends and distributions	(113)	(97)	[1]
Payments of debt issuance costs	5	12	[1]
Proceeds from the revolving credit facility	35	0	[1]
Repayments of Lines of Credit	90	0	[1]
Proceeds from the issuance of long-term debt	227	99	[1]
Payments for long-term debt	(285)	(172)	[1]
Net Cash Used in Financing Activities	(62)	(177)	[1]
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(47)	(198)	[1]
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	316	498	[1]
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 269	$ 300	[1]
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business NRG Yield, Inc., together with its consolidated subsidiaries, or the Company, is a dividend growth-oriented company that has historically served as the primary vehicle through which NRG owns, operates and acquires contracted renewable and conventional generation and thermal infrastructure assets. The Company believes it is well positioned to be a premier company for investors seeking stable and growing dividend income from a diversified portfolio of lower-risk assets. The Company owns a diversified portfolio of contracted renewable and conventional generation and thermal infrastructure assets in the U.S. The Company’s contracted generation portfolio collectively represents 5,118 net MW as of June 30, 2018 . Nearly all of these assets sell substantially all of their output pursuant to long-term offtake agreements with creditworthy counterparties. The weighted average remaining contract duration of these offtake agreements was approximately 15 years as of June 30, 2018 based on CAFD. The Company also owns thermal infrastructure assets with an aggregate steam and chilled water capacity of 1,392 net MWt and electric generation capacity of 133 net MW. These thermal infrastructure assets provide steam, hot and/or chilled water, and, in some instances, electricity to commercial businesses, universities, hospitals and governmental units in multiple locations, principally through long-term contracts or pursuant to rates regulated by state utility commissions. NRG Yield, Inc. consolidates the results of NRG Yield LLC through its controlling interest, with NRG's interest shown as noncontrolling interest in the financial statements. The holders of NRG Yield, Inc.'s outstanding shares of Class A and Class C common stock are entitled to dividends as declared. NRG receives its distributions from NRG Yield LLC through its ownership of NRG Yield LLC Class B and Class D units. The following table represents the structure of the Company as of June 30, 2018 : On February 6, 2018, Global Infrastructure Partners, or GIP, entered into a purchase and sale agreement with NRG, or the NRG Transaction, for the acquisition of NRG's full ownership interests in the Company and NRG's renewable development and operations platform. The NRG Transaction is subject to certain closing conditions, including customary legal and regulatory approvals. As of July 31, 2018, all regulatory approvals have been obtained and the Company expects the NRG Transaction to close in the third quarter of 2018. NRG is currently the Company's controlling stockholder and the Company has been highly dependent on NRG for, among other things, growth opportunities and management and administration services. In connection with the NRG Transaction, the Company entered into a Consent and Indemnity Agreement with NRG and GIP setting forth key terms and conditions of the Company's consent to the NRG Transaction. For further discussion of the NRG Transaction, refer to Item 1 - Business in the Company's 2017 Form 10-K. For risks related to the NRG Transaction and the Company's relationship with NRG see Part I, Item 1A, Risk Factors in the Company's 2017 Form 10-K. As of June 30, 2018 , the Company's operating assets are comprised of the following projects: Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Conventional El Segundo 100 % 550 Southern California Edison 2023 GenConn Devon 50 % 95 Connecticut Light & Power 2040 GenConn Middletown 50 % 95 Connecticut Light & Power 2041 Marsh Landing 100 % 720 Pacific Gas and Electric 2023 Walnut Creek 100 % 485 Southern California Edison 2023 1,945 Utility Scale Solar Agua Caliente 16 % 46 Pacific Gas and Electric 2039 Alpine 100 % 66 Pacific Gas and Electric 2033 Avenal 50 % 23 Pacific Gas and Electric 2031 Avra Valley 100 % 26 Tucson Electric Power 2032 Blythe 100 % 21 Southern California Edison 2029 Borrego 100 % 26 San Diego Gas and Electric 2038 CVSR 100 % 250 Pacific Gas and Electric 2038 Desert Sunlight 250 25 % 63 Southern California Edison 2034 Desert Sunlight 300 25 % 75 Pacific Gas and Electric 2039 Kansas South 100 % 20 Pacific Gas and Electric 2033 Roadrunner 100 % 20 El Paso Electric 2031 TA High Desert 100 % 20 Southern California Edison 2033 Utah Solar Portfolio (b) (e) 50 % 265 PacifiCorp 2036 921 Distributed Solar Apple I LLC Projects 100 % 9 Various 2032 AZ DG Solar Projects 100 % 5 Various 2025 - 2033 SPP Projects 100 % 25 Various 2026 - 2037 Other DG Projects 100 % 13 Various 2023 - 2039 52 Wind Alta I 100 % 150 Southern California Edison 2035 Alta II 100 % 150 Southern California Edison 2035 Alta III 100 % 150 Southern California Edison 2035 Alta IV 100 % 102 Southern California Edison 2035 Alta V 100 % 168 Southern California Edison 2035 Alta X (b) 100 % 137 Southern California Edison 2038 Alta XI (b) 100 % 90 Southern California Edison 2038 Buffalo Bear 100 % 19 Western Farmers Electric Co-operative 2033 Crosswinds (b) (f) 99 % 21 Corn Belt Power Cooperative 2027 Elbow Creek (b) (f) 100 % 122 NRG Power Marketing LLC 2022 Elkhorn Ridge (b) (f) 66.7 % 54 Nebraska Public Power District 2029 Forward (b) (f) 100 % 29 Constellation NewEnergy, Inc. 2022 Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Goat Wind (b) (f) 100 % 150 Dow Pipeline Company 2025 Hardin (b) (f) 99 % 15 Interstate Power and Light Company 2027 Laredo Ridge 100 % 80 Nebraska Public Power District 2031 Lookout (b) (f) 100 % 38 Southern Maryland Electric Cooperative 2030 Odin (b) (f) 99.9 % 20 Missouri River Energy Services 2028 Pinnacle 100 % 55 Maryland Department of General Services and University System of Maryland 2031 San Juan Mesa (b) (f) 75 % 90 Southwestern Public Service Company 2025 Sleeping Bear (b) (f) 100 % 95 Public Service Company of Oklahoma 2032 South Trent 100 % 101 AEP Energy Partners 2029 Spanish Fork (b) (f) 100 % 19 PacifiCorp 2028 Spring Canyon II (b) 90.1 % 29 Platte River Power Authority 2039 Spring Canyon III (b) 90.1 % 25 Platte River Power Authority 2039 Taloga 100 % 130 Oklahoma Gas & Electric 2031 Wildorado (b) (f) 100 % 161 Southwestern Public Service Company 2027 2,200 Thermal NRG Energy Center Dover LLC 100 % 103 NRG Power Marketing LLC 2018 Thermal generation 100 % 30 Various Various 133 Total net generation capacity (c) 5,251 Thermal equivalent MWt (d) 100 % 1,392 Various Various (a) Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018 . (b) Projects are part of tax equity arrangements. (c) The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs. (d) For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers. (e) Represents interests in Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC, all acquired as part of the March 2017 Drop Down Assets (ownership percentage is based upon cash to be distributed). (f) Projects are part of NRG Wind TE Holdco portfolio. In addition to the facilities owned or leased in the table above, the Company entered into partnerships to own or purchase solar power generation projects, as well as other ancillary related assets from a related party via intermediate funds. The Company does not consolidate these partnerships and accounts for them as equity method investments. The Company's net interest in these projects is 268 MW based on cash to be distributed as of June 30, 2018 . For further discussions, see Note 4 , Investments Accounted for by the Equity Method and Variable Interest Entities of this Form 10-Q and Note 5 , Investments Accounted for by the Equity Method and Variable Interest Entities to the consolidated financial statements included in the Company's 2017 Form 10-K. Substantially all of the Company's generation assets are under long-term contractual arrangements for the output or capacity from these assets. The thermal assets are comprised of district energy systems and combined heat and power plants that produce steam, hot water and/or chilled water and, in some instances, electricity at a central plant. Certain district energy systems are subject to rate regulation by state public utility commissions (although they may negotiate certain rates) while the other district energy systems have rates determined by negotiated bilateral contracts. Recast of the Historical Financial Statements As described in Note 3 , Business Acquisitions , on March 30, 2018, the Company acquired 100% of NRG's interests in Buckthorn Renewables, LLC, which owned a 154 MW construction-stage utility-scale solar generation project, or the Buckthorn Solar Drop Down Asset, for cash consideration of approximately $42 million , subject to working capital adjustments, plus assumed non-recourse debt of approximately $183 million and non-controlling interest of $19 million (as of the acquisition date) attributable to the Class A member. On May 31, 2018, $132 million of non-recourse debt was converted to a term loan with an expected maturity of May 2025, and the remainder of the non-recourse debt was repaid with the final proceeds from the Class A member upon the project reaching substantial completion in May 2018. The purchase price was funded with cash on hand and borrowings from the revolving credit facility. The acquisition of the Buckthorn Solar Drop Down Asset was accounted for as a transfer of entities under common control. The accounting guidance requires retrospective combination of the entities for all periods presented as if the combinations had been in effect from the beginning of the financial statement period or from the date the entities were under common control (if later than the beginning of the financial statement period). The recast of the Company's financial statements for the Buckthorn Solar Drop Down Asset did not affect the historical net income attributable to NRG Yield, Inc., weighted average number of shares outstanding, earnings per share or dividends. Additionally, as described in Note 3 , Business Acquisitions , during the year ended December 31, 2017, the Company acquired the November 2017 Drop Down Assets and August 2017 Drop Down Assets from NRG. Similarly to the Buckthorn Solar Drop Down Asset, the Company recast its historical financial statements to combine the entities for the periods presented as if the combinations had been in effect from the beginning of the financial statements period. The recast of the Company's financial statements for the November 2017 Drop Down Assets and August 2017 Drop Down Assets did not affect the historical net income attributable to NRG Yield, Inc., weighted average number of shares outstanding, earnings per share or dividends. The accompanying unaudited interim consolidated financial statements have been prepared in accordance with the SEC’s regulations for interim financial information and with the instructions to Form 10-Q. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The following notes should be read in conjunction with the accounting policies and other disclosures as set forth in the notes to the consolidated financial statements included in the Company's 2017 Form 10-K. Interim results are not necessarily indicative of results for a full year. In the opinion of management, the accompanying unaudited interim consolidated financial statements contain all material adjustments consisting of normal and recurring accruals necessary to present fairly the Company's consolidated financial position as of June 30, 2018 , and the results of operations, comprehensive income (loss) and cash flows for the six months ended June 30, 2018 and 2017 .

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions. These estimates and assumptions impact the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could be different from these estimates. Accumulated Depreciation, Accumulated Amortization The following table presents the accumulated depreciation included in the property, plant and equipment, net, and accumulated amortization included in intangible assets, net, respectively, as of June 30, 2018 and December 31, 2017 : June 30, 2018 December 31, 2017 (In millions) Property, Plant and Equipment Accumulated Depreciation $ 1,428 $ 1,285 Intangible Assets Accumulated Amortization 272 237 Noncontrolling Interests Stockholders' equity represents the equity associated with the Class A and Class C common stockholders, the equity associated with the Class B and Class D common stockholder, NRG, and the third-party interests under certain tax equity arrangements are classified as noncontrolling interests. The following table reflects the changes in the Company's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 as previously reported (a) $ 391 Net Assets of Buckthorn Solar Drop Down Asset as of December 31, 2017 21 Balance as of December 31, 2017 as recast $ 412 Capital contributions from tax equity investors, net of distributions 109 Payment for the Buckthorn Solar Drop Down Asset (42 ) Non cash distributions to NRG in connection with the UPMC Thermal Project Asset Acquisition (13 ) Pre-acquisition net income of the Buckthorn Solar Drop Down Asset 4 Comprehensive income 10 Non-cash adjustment for change in tax basis of assets 2 Distributions to NRG, net (63 ) Balance as of June 30, 2018 $ 419 (a) As previously reported in the Company's Form 10-K for the year ended December 31, 2017. NRG Yield LLC Distributions to NRG The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the six months ended June 30, 2018 : Second Quarter 2018 First Quarter 2018 Distributions per Class B Unit $ 0.309 $ 0.298 Distributions per Class D Unit $ 0.309 $ 0.298 On July 24, 2018 , NRG Yield LLC declared a distribution on its Class A, Class B, Class C and Class D units of $0.320 per unit payable on September 18, 2018 to unit holders of record as of September 4, 2018 . Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606, Revenue from Contracts with Customers, or Topic 606, using the modified retrospective method applied to contracts which were not completed as of the adoption date, with no adjustment required to the financial statements upon adoption. Following the adoption of the new standard, the Company’s revenue recognition of its contracts with customers remains materially consistent with its historical practice. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company's policies with respect to its various revenue streams are detailed below. In general, the Company applies the invoicing practical expedient to recognize revenue for the revenue streams detailed below, except in circumstances where the invoiced amount does not represent the value transferred to the customer. Thermal Revenues Steam and chilled water revenue is recognized as the Company transfers the product to the customer, based on customer usage as determined by meter readings taken at month-end. Some locations read customer meters throughout the month, and recognize estimated revenue for the period between meter read date and month-end. For thermal contracts, the Company’s performance obligation to deliver steam and chilled water is satisfied over time and revenue is recognized based on the invoiced amount. The Thermal Business subsidiaries collect and remit state and local taxes associated with sales to their customers, as required by governmental authorities. These taxes are presented on a net basis in the income statement. As contracts for steam and chilled water are long-term contracts, the Company has performance obligations under these contracts that have not yet been satisfied. These performance obligations have transaction prices that are both fixed and variable, and that vary based on the contract duration, customer type, inception date and other contract-specific factors. For the fixed price contracts, the Company cannot accurately estimate the amount of its unsatisfied performance obligations as it will vary based on customer usage, which will depend on factors such as weather and customer activity. Power Purchase Agreements, or PPAs The majority of the Company’s revenues are obtained through PPAs or other contractual agreements. Energy, capacity and where applicable, renewable attributes, from the majority of the Company’s renewable energy assets and certain conventional energy plants is sold through long-term PPAs and tolling agreements to a single counterparty, which is often a utility or commercial customer. The majority of these PPAs are accounted for as leases. ASC 840 requires the minimum lease payments received to be amortized over the term of the lease and contingent rentals are recorded when the achievement of the contingency becomes probable. Judgment is required by management in determining the economic life of each generating facility, in evaluating whether certain lease provisions constitute minimum payments or represent contingent rent and other factors in determining whether a contract contains a lease and whether the lease is an operating lease or capital lease. Renewable Energy Credits, or RECs As stated above, renewable energy credits, or RECs, are usually sold through long-term PPAs. Revenue from the sale of self-generated RECs is recognized when related energy is generated and simultaneously delivered even in cases where there is a certification lag as it has been deemed to be perfunctory. In a bundled contract to sell energy, capacity and/or self-generated RECs, all performance obligations are deemed to be delivered at the same time and hence, timing of recognition of revenue for all performance obligations is the same and occurs over time. In such cases, it is often unnecessary to allocate transaction price to multiple performance obligations. Sale of Emission Allowances The Company records its bank of emission allowances as part of intangible assets. From time to time, management may authorize the transfer of emission allowances in excess of usage from the Company's emission bank to intangible assets held-for-sale for trading purposes. The Company records the sale of emission allowances on a net basis within operating revenue in the Company's consolidated statements of operations. Disaggregated Revenues The following tables represent the Company’s disaggregation of revenue from contracts with customers for the three and six months ended June 30, 2018 , along with the reportable segment for each category: Three months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Total Energy revenue (a) $ 2 $ 193 $ 43 $ 238 Capacity revenue (a) 85 — 2 87 Contract amortization (2 ) (16 ) — (18 ) Total operating revenue 85 177 45 307 Less: Lease revenue (87 ) (179 ) (1 ) (267 ) Less: Contract amortization 2 16 — 18 Total revenue from contracts with customers $ — $ 14 $ 44 $ 58 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 2 $ 179 $ 1 $ 182 Capacity Revenue 85 — — 85 87 179 1 267 Six months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Total Energy revenue (b) $ 3 $ 306 $ 89 $ 398 Capacity revenue (b) 164 — 5 169 Contract amortization (3 ) (31 ) (1 ) (35 ) Total operating revenue 164 275 93 532 Less: Lease revenue (167 ) (280 ) (1 ) (448 ) Less: Contract amortization 3 31 1 35 Total revenue from contracts with customers $ — $ 26 $ 93 $ 119 (b) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 3 $ 280 $ 1 $ 284 Capacity Revenue 164 — — 164 167 280 1 448 Contract Amortization Assets and liabilities recognized from power sales agreements assumed through acquisitions related to the sale of electric capacity and energy in future periods for which the fair value has been determined to be significantly less (more) than market are amortized to revenue over the term of each underlying contract based on actual generation and/or contracted volumes or on a straight-line basis, where applicable. Contract Balances The following table reflects the contract assets and liabilities included on the Company’s balance sheet as of June 30, 2018 : (In millions) June 30, 2018 Accounts receivable, net - Contracts with customers $ 29 Accounts receivable, net - Leases 103 Total accounts receivable, net $ 132 Income Taxes NRG Yield, Inc. is included in certain NRG consolidated unitary state tax return filings which is reflected in NRG Yield, Inc.'s state effective tax rate. If NRG Yield, Inc. filed under a separate standalone methodology, there would be an additional state tax expense of approximately $2 million as of June 30, 2018 due to a change in the NRG Yield, Inc. state effective tax rate. Reclassifications Certain prior-year amounts have been reclassified for comparative purposes. Recent Accounting Developments - Not Yet Adopted ASU 2016-02 — In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), or Topic 842, with the objective to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and to improve financial reporting by expanding the related disclosures. The guidance in Topic 842 provides that a lessee that may have previously accounted for a lease as an operating lease under current GAAP should recognize the assets and liabilities that arise from a lease on the balance sheet. In addition, Topic 842 expands the required quantitative and qualitative disclosures with regards to lease arrangements. The Company will adopt the standard effective January 1, 2019 and expects to elect certain of the practical expedients permitted, including the expedient that permits the Company to retain its existing lease assessment and classification. The Company is currently working through an adoption plan and evaluating the anticipated impact on the Company's results of operations, cash flows and financial position. While the Company is currently evaluating the impact the new guidance will have on its financial position and results of operations, the Company expects to recognize lease liabilities and right of use assets. The extent of the increase to assets and liabilities associated with these amounts remains to be determined pending the Company’s review of its existing lease contracts and service contracts which may contain embedded leases. While this review is still in process, the Company believes the adoption of Topic 842 may be material to its financial statements. The Company is continuing to monitor potential changes to Topic 842 that have been proposed by the FASB and will assess any necessary changes to the implementation as the guidance is updated.

Business Acquisitions Business

Business Acquisitions Business Acquisitions (Notes)	6 Months Ended
	Jun. 30, 2018
Business Acquisitions [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	Business Acquisitions 2018 Acquisitions UPMC Thermal Project Asset Acquisition — On June 19, 2018, upon reaching substantial completion, the Company acquired from NRG the UPMC Thermal Project for cash consideration of $84 million , subject to working capital adjustments. The Company also recorded a payable of $4 million to be paid to NRG upon final completion of the project pursuant to the EPC agreement, as discussed in Note 12 , Related Party Transactions . The project adds 73 MWt of thermal equivalent capacity and 7.5 MW of emergency backup thermal capacity to the Company's portfolio. The transaction is reflected in the Company's Thermal segment. The acquisition was funded with the proceeds from the sale of the Series E Notes and Series F Notes, as further described in Note 7 , Long-term Debt . The assets transferred to the Company relate to interests under common control by NRG and were recorded at book value in accordance with ASC 805-50, Business Combinations - Related Issues . The difference between the purchase price and book value of the assets was recorded as a distribution to NRG and decreased the balance of its noncontrolling interest. The acquisition was determined to be an asset acquisition and not a business combination, therefore no recast of the historical financial information was deemed necessary. Central CA Fuel Cell 1, LLC — On April 18, 2018 , the Company acquired the Central CA Fuel Cell 1, LLC project in Tulare, California from FuelCell Energy Finance, Inc., for cash consideration of $11 million , subject to working capital adjustments. The project adds 2.8 MW of thermal capacity to the Company's portfolio, with a 20 -year PPA contract with the City of Tulare. The transaction is reflected in the Company's Thermal segment. Buckthorn Solar Drop Down Asset — On March 30, 2018 , the Company acquired 100% of NRG's interests in Buckthorn Renewables, LLC, which owned a 154 MW construction-stage utility-scale solar generation project located in Texas, or the Buckthorn Solar Drop Down Asset, for cash consideration of approximately $42 million , subject to working capital adjustments. The Company also assumed non-recourse debt of $ 183 million and non-controlling interest of $19 million (as of acquisition date) attributable to the Class A member, as further described below. The Company converted $132 million of non-recourse debt to a term loan and the remainder of the outstanding debt was paid down with the contribution from the Class A member in the amount of $80 million upon the project reaching substantial completion in May 2018. The purchase price for the Buckthorn Solar Drop Down Asset was funded with cash on hand and borrowings from the Company's revolving credit facility. The assets and liabilities transferred to the Company relate to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combinations - Related Issues . The difference between the cash paid and historical value of the entities' equity was recorded as a distribution to NRG and decreased the balance of its noncontrolling interest. Since the transaction constituted a transfer of net assets under common control, the guidance requires retrospective combination of the entities for all periods presented as if the combination had been in effect since the inception of common control. Buckthorn Solar Portfolio, LLC, a wholly owned subsidiary of Buckthorn Renewables, LLC, is the Class B member in a tax equity partnership, Buckthorn Holdings, LLC, the owner of the Buckthorn Solar Drop Down Asset. The Class A member is a tax equity investor, or TE investor, who receives 99% of allocations of taxable income and other items through the six month anniversary of the placed in service date, at which time the allocations change to 67% through the last calendar year before the flip point, and then back to 99% through the flip point (which occurs when the TE Investor obtains a specified return on its initial investment), at which time the allocations to the TE Investor change to 5% for all the periods thereafter. Before the flip point, the TE investor would receive a priority distribution of distributable cash, as defined, plus a percentage of remaining distributable cash after the priority distribution subject to a percentage cap. The project sells power under a 25-year PPA to the City of Georgetown, Texas, which commenced in July 2018. The following is a summary of net assets transferred in connection with the acquisition of the Buckthorn Solar Drop Down Asset as of March 31, 2018: (In millions) Assets: Current assets $ 20 Property, plant and equipment 212 Non-current assets 3 Total assets 235 Liabilities: Debt (Current and non-current) (a) 176 Other current and non-current liabilities 15 Total liabilities 191 Less: noncontrolling interest 19 Net assets acquired $ 25 (a) Net of $7 million of net debt issuance costs. 2017 Acquisitions November 2017 Drop Down Assets — On November 1, 2017, the Company acquired a 38 MW solar portfolio primarily comprised of assets from NRG's Solar Power Partners (SPP) funds and other projects developed by NRG , for cash consideration of $74 million , including working capital adjustments, plus assumed non-recourse debt of $26 million . The purchase price for the November 2017 Drop Down Assets was funded with cash on hand. The assets and liabilities transferred to the Company relate to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combinations - Related Issues . The difference between the cash paid and historical value of the entities' equity was recorded as a contribution from NRG and increased the balance of its noncontrolling interest. Since the transaction constituted a transfer of net assets under common control, the guidance requires retrospective combination of the entities for all periods presented as if the combination has been in effect since the inception of common control. August 2017 Drop Down Assets — On August 1, 2017, the Company acquired the remaining 25% interest in NRG Wind TE Holdco, a portfolio of 12 wind projects, from NRG for total cash consideration of $44 million , including working capital adjustments. The purchase agreement also included potential additional payments to NRG dependent upon actual energy prices for merchant periods beginning in 2027, which were estimated and accrued as contingent consideration in the amount of $8 million . The Company originally acquired 75% of NRG Wind TE Holdco on November 3, 2015, or November 2015 Drop Down Assets, which were consolidated with 25% of the net assets recorded as noncontrolling interest. The assets and liabilities transferred to the Company related to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combination - Related Issues. As the Company had reflected NRG's 25% ownership of NRG Wind TE Holdco in noncontrolling interest, the difference between the cash paid of $44 million , net of the contingent consideration of $8 million , and the historical value of the remaining 25% of $87 million as of July 31, 2017, was recorded as an adjustment to NRG's noncontrolling interest. Since the transaction constituted a transfer of entities under common control, the accounting guidance requires retrospective combination of the entities for all periods presented as if the combination has been in effect from the beginning of the financial statement period or from the date the entities were under common control (if later than the beginning of the financial statement period). The following tables present a summary of the Company's historical information combining the financial information for the Buckthorn Solar Drop Down Asset, November 2017 Drop Down Assets and August 2017 Drop Down Assets transferred in connection with the acquisition: Three months ended June 30, 2017 As Previously Reported (a) Buckthorn Solar Drop Down Asset November 2017 Drop Down Assets August 2017 Drop Down Assets As Currently Reported (In millions) Total operating revenues $ 284 $ — $ 4 $ — $ 288 Operating income 122 — 3 — 125 Net income (loss) 45 (3 ) 2 — 44 Less: Pre-acquisition net (loss) income of Drop Down Assets — (3 ) 2 3 2 Less: Income (loss) attributable to noncontrolling interests 17 — — (3 ) 14 Net income attributable to NRG Yield, Inc. 28 — — — 28 Six months ended June 30, 2017 As Previously Reported (a) Buckthorn Solar Drop Down Asset November 2017 Drop Down Assets August 2017 Drop Down Assets As Currently Reported (In millions) Total operating revenues $ 502 $ — $ 7 $ — $ 509 Operating income 176 — 3 — 179 Net income (loss) 44 (3 ) 1 — 42 Less: Pre-acquisition net income (loss) of Drop Down Assets 12 (3 ) 1 5 15 Less: Income (loss) attributable to noncontrolling interests 7 — — (5 ) 2 Net income attributable to NRG Yield, Inc. 25 — — — 25 (a) As previously reported in the Company's Form 10-Q for the quarter ended June 30, 2017. March 2017 Drop Down Assets — On March 27, 2017, the Company acquired the following interests from NRG: (i) Agua Caliente Borrower 2 LLC, which owns a 16% interest (approximately 31% of NRG's 51% interest) in the Agua Caliente solar farm, one of the ROFO Assets, representing ownership of approximately 46 net MW of capacity and (ii) NRG's interests in the Utah Solar Portfolio. Agua Caliente is located in Yuma County, AZ and sells power subject to a 25 -year PPA with Pacific Gas and Electric, with 22 years remaining on that contract. The seven utility-scale solar farms in the Utah Solar Portfolio are owned by the following entities: Four Brothers Capital, LLC, Iron Springs Capital, LLC, and Granite Mountain Capital, LLC. These utility-scale solar farms achieved commercial operations in 2016, sell power subject to 20 -year PPAs with PacifiCorp, a subsidiary of Berkshire Hathaway and are part of a tax equity structure with Dominion Solar Projects III, Inc., or Dominion, through which the Company is entitled to receive 50% of cash to be distributed, as further described below. The Company paid cash consideration of $128 million , which includes $3 million of final net working capital adjustment received by the Company from NRG. The acquisition of the March 2017 Drop Down Assets was funded with cash on hand. The Company recorded the acquired interests as equity method investments. The Company also assumed non-recourse debt of $41 million and $287 million on Agua Caliente Borrower 2 LLC and the Utah Solar Portfolio, respectively, as well as its pro-rata share of non-recourse project-level debt of Agua Caliente Solar LLC, as further described in Note 4 , Investments Accounted for by the Equity Method and Variable Interest Entities . The assets and liabilities transferred to the Company relate to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combination - Related Issues. The difference between the cash paid and the historical value of the entities' equity of $8 million was recorded as an adjustment to NRG's noncontrolling interest. Since the transaction constituted a transfer of entities under common control, the accounting guidance requires retrospective combination of the entities for all periods presented as if the combination has been in effect from the beginning of the financial statement period or from the date the entities were under common control (if later than the beginning of the financial statement period).

Variable Interest Entities

Variable Interest Entities	6 Months Ended
	Jun. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments Accounted for by the Equity Method and Variable Interest Entities	Investments Accounted for by the Equity Method and Variable Interest Entities Entities that are Consolidated The Company has a controlling financial interest in certain entities which have been identified as VIEs under ASC 810, Consolidations, or ASC 810. These arrangements are primarily related to tax equity arrangements entered into with third parties in order to monetize certain tax credits associated with wind facilities, as further described in Note 5 , Investments Accounted for by the Equity Method and Variable Interest Entities , to the consolidated financial statements included in the Company's 2017 Form 10-K. Buckthorn Renewables, LLC — As described in Note 3 , Business Acquisitions , on March 30, 2018, the Company acquired 100% of NRG’s interest in a 154 MW construction-stage utility-scale solar generation project, Buckthorn Renewables, LLC, which owns 100% interest in Buckthorn Solar Portfolio, LLC, which in turn owns 100% of the Class B membership interests in Buckthorn Holdings, LLC for total consideration of approximately $42 million , subject to working capital adjustments. The Company also assumed non-recourse debt of $ 183 million and non-controlling interest of $19 million attributable to the Class A member, as further described below. On May 31, 2018, $132 million of non-recourse debt was converted to a term loan with an expected maturity of May 2025, and the remainder of the non-recourse debt was repaid with final proceeds from the Class A member upon the project reaching substantial completion in May 2018. Buckthorn Holdings, LLC is a tax equity fund, which is a variable interest entity that is consolidated by Buckthorn Solar Portfolio, LLC. The Company is the primary beneficiary, through its position as managing member, and indirectly consolidates Buckthorn Holdings, LLC through Buckthorn Solar Portfolio, LLC. The Class A member is a tax equity investor who made its initial capital contribution of $19 million on March 30, 2018, which is reflected as noncontrolling interest on the Company’s consolidated balance sheet. The project achieved substantial completion in May 2018, at which time the remaining contributions in the amount of $80 million were funded. The Company utilizes the HLBV method to determine the net income or loss allocated to the tax equity investor noncontrolling interest. The Company recorded $51 million of loss attributable to its non-controlling interest in Buckthorn Renewables, LLC during the period ended June 30, 2018 . Summarized financial information for the Company's consolidated VIEs consisted of the following as of June 30, 2018 : (In millions) NRG Wind TE Holdco Alta Wind TE Holdco Spring Canyon Buckthorn Renewables, LLC Other current and non-current assets $ 163 $ 23 $ 1 $ 24 Property, plant and equipment 362 423 93 226 Intangible assets 2 256 — — Total assets 527 702 94 250 Current and non-current liabilities 184 9 4 141 Total liabilities 184 9 4 141 Noncontrolling interest 10 72 48 48 Net assets less noncontrolling interests $ 333 $ 621 $ 42 $ 61 Entities that are not Consolidated The Company has interests in entities that are considered VIEs under ASC 810, but for which it is not considered the primary beneficiary. The Company accounts for its interests in these entities under the equity method of accounting, as further described in Note 5 , Investments Accounted for by the Equity Method and Variable Interest Entities , to the consolidated financial statements included in the Company's 2017 Form 10-K. The Company's maximum exposure to loss as of June 30, 2018 , is limited to its equity investment in the unconsolidated entities, as further summarized in the table below: (In millions) Maximum exposure to loss Four Brothers Solar, LLC $ 209 GenConn Energy LLC 100 NRG DGPV Holdco 1 LLC 81 Granite Mountain Holdings, LLC 76 NRG DGPV Holdco 3 LLC 75 NRG DGPV Holdco 2 LLC 61 Iron Springs Holdings, LLC 53 NRG RPV Holdco 1 LLC 46 NRG DGPV Holdco 1 LLC — The Company invested $4 million of cash during the six months ended June 30, 2018 into DGPV Holdco 1 LLC and recorded $3 million due to NRG in accounts payable - affiliate as of June 30, 2018 to be funded in tranches as the project milestones are completed. The Company owns approximately 52 MW of distributed solar capacity, based on cash to be distributed, with a weighted average remaining contract life of approximately 18 years as of June 30, 2018 . NRG DGPV Holdco 3 LLC — The Company invested $12 million of cash during the six months ended June 30, 2018 into DGPV Holdco 3 LLC and recorded $10 million due to NRG in accounts payable - affiliate as of June 30, 2018 to be funded in tranches as the project milestones are completed. The Company owns approximately 59 MW of distributed solar capacity, based on cash to be distributed, with a weighted average remaining contract life of approximately 21 years as of June 30, 2018 . Utah Solar Portfolio — As described in Note 3 , Business Acquisitions , on March 27, 2017, as part of the March 2017 Drop Down Assets acquisition, the Company acquired from NRG 100% of the Class A equity interests in the Utah Solar Portfolio, comprised of Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC. The Class B interests of the Utah Solar Portfolio are owned by a tax equity investor, who receives 99% of allocations of taxable income and other items until the flip point, which occurs when the tax equity investor obtains a specified return on its initial investment, at which time the allocations to the tax equity investor change to 50% . The Company generally receives 50% of distributable cash throughout the term of the tax-equity arrangements. The three entities comprising the Utah Solar Portfolio are VIEs. As the Company is not the primary beneficiary, the Company uses the equity method of accounting to account for its interests in the Utah Solar Portfolio. The Company utilizes the HLBV method to determine its share of the income or losses in the investees. Non-recourse project-level debt of unconsolidated affiliates Agua Caliente Financing — As described in Note 3 , Business Acquisitions , on March 27, 2017, the Company acquired a 16% interest in the Agua Caliente solar facility through its acquisition of Agua Caliente Borrower 2 LLC. As of June 30, 2018 , Agua Caliente Solar LLC, the direct owner of the Agua Caliente solar facility, had $812 million outstanding under the Agua Caliente financing agreement with the Federal Financing Bank, or FFB, borrowed to finance the costs of constructing the facility. The Company's pro-rata share of the Agua Caliente financing arrangement was $130 million as of June 30, 2018 . Amounts borrowed under the Agua Caliente financing agreement accrue interest at a fixed rate based on U.S. Treasury rates plus a spread of 0.375% , mature in 2037 and are secured by the assets of Agua Caliente Solar LLC. The loans provided by the FFB are guaranteed by the U.S. DOE.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair Value Accounting under ASC 820 ASC 820 establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows: • Level 1—quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date. • Level 2—inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. • Level 3—unobservable inputs for the asset or liability only used when there is little, if any, market activity for the asset or liability at the measurement date. In accordance with ASC 820, the Company determines the level in the fair value hierarchy within which each fair value measurement in its entirety falls, based on the lowest level input that is significant to the fair value measurement. For cash and cash equivalents, restricted cash, accounts receivable, accounts receivable — affiliate, accounts payable, current portion of the accounts payable — affiliates, accrued expenses and other liabilities, the carrying amounts approximate fair value because of the short-term maturity of those instruments and are classified as Level 1 within the fair value hierarchy. The estimated carrying amounts and fair values of the Company’s recorded financial instruments not carried at fair market value are as follows: As of June 30, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable $ 6 $ 6 $ 13 $ 13 Liabilities: Long-term debt, including current portion (a) $ 5,957 $ 5,936 $ 6,066 $ 6,099 (a) Excludes deferred financing costs, which are recorded as a reduction to long-term debt on the Company's consolidated balance sheets. The fair value of the Company's publicly-traded long-term debt is based on quoted market prices and is classified as Level 2 within the fair value hierarchy. The fair value of debt securities, non-publicly traded long-term debt and certain notes receivable of the Company are based on expected future cash flows discounted at market interest rates, or current interest rates for similar instruments with equivalent credit quality and are classified as Level 3 within the fair value hierarchy. The following table presents the level within the fair value hierarchy for long-term debt, including current portion as of June 30, 2018 and December 31, 2017 : As of June 30, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 1,456 $ 4,480 $ 1,502 $ 4,597 Recurring Fair Value Measurements The Company records its derivative assets and liabilities at fair value on its consolidated balance sheet. The following table presents assets and liabilities measured and recorded at fair value on the Company's consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of June 30, 2018 As of December 31, 2017 Fair Value (a) Fair Value (a) (In millions) Level 2 Level 2 Derivative assets: Commodity contracts $ — $ 1 Interest rate contracts 24 1 Total assets 24 2 Derivative liabilities: Commodity contracts 1 1 Interest rate contracts 17 48 Total liabilities $ 18 $ 49 (a) There were no derivative assets or liabilities classified as Level 1 or Level 3 as of June 30, 2018 and December 31, 2017 . Derivative Fair Value Measurements The Company's contracts are non-exchange-traded and valued using prices provided by external sources. For the Company’s energy markets, management receives quotes from multiple sources. To the extent that multiple quotes are received, the prices reflect the average of the bid-ask mid-point prices obtained from all sources believed to provide the most liquid market for the commodity. The fair value of each contract is discounted using a risk free interest rate. In addition, a credit reserve is applied to reflect credit risk, which is, for interest rate swaps, calculated based on credit default swaps using the bilateral method. For commodities, to the extent that the net exposure under a specific master agreement is an asset, the Company uses the counterparty’s default swap rate. If the net exposure under a specific master agreement is a liability, the Company uses NRG's default swap rate. For interest rate swaps and commodities, the credit reserve is added to the discounted fair value to reflect the exit price that a market participant would be willing to receive to assume the liabilities or that a market participant would be willing to pay for the assets. As of June 30, 2018 , the credit reserve was $1 million in interest expense . It is possible that future market prices could vary from those used in recording assets and liabilities and such variations could be material. Concentration of Credit Risk In addition to the credit risk discussion in Note 2 , Summary of Significant Accounting Policies , to the consolidated financial statements included in the Company's 2017 Form 10-K, the following is a discussion of the concentration of credit risk for the Company's financial instruments. Credit risk relates to the risk of loss resulting from non-performance or non-payment by counterparties pursuant to the terms of their contractual obligations. The Company monitors and manages credit risk through credit policies that include: (i) an established credit approval process; (ii) daily monitoring of counterparties' credit limits; (iii) the use of credit mitigation measures such as margin, collateral, prepayment arrangements, or volumetric limits; (iv) the use of payment netting agreements; and (v) the use of master netting agreements that allow for the netting of positive and negative exposures of various contracts associated with a single counterparty. Risks surrounding counterparty performance and credit could ultimately impact the amount and timing of expected cash flows. The Company seeks to mitigate counterparty risk by having a diversified portfolio of counterparties. Counterparty credit exposure includes credit risk exposure under certain long-term agreements, including solar and other PPAs. As external sources or observable market quotes are not available to estimate such exposure, the Company estimates the exposure related to these contracts based on various techniques including, but not limited to, internal models based on a fundamental analysis of the market and extrapolation of observable market data with similar characteristics. Based on these valuation techniques, as of June 30, 2018 , credit risk exposure to these counterparties attributable to the Company's ownership interests was approximately $2.6 billion for the next five years . The majority of these power contracts are with utilities with strong credit quality and public utility commission or other regulatory support. However, such regulated utility counterparties can be impacted by changes in government regulations, which the Company is unable to predict.

Accounting for Derivative Instr

Accounting for Derivative Instruments and Hedging Activities	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Accounting for Derivative Instruments and Hedging Activities	Accounting for Derivative Instruments and Hedging Activities This footnote should be read in conjunction with the complete description under Note 7 , Accounting for Derivative Instruments and Hedging Activities , to the consolidated financial statements included in the Company's 2017 Form 10-K. Energy-Related Commodities As of June 30, 2018 , the Company had energy-related derivative instruments extending through 2020. At June 30, 2018 , these contracts were not designated as cash flow or fair value hedges. Interest Rate Swaps As of June 30, 2018 , the Company had interest rate derivative instruments on non-recourse debt extending through 2041, a portion of which are designated as cash flow hedges. Volumetric Underlying Derivative Transactions The following table summarizes the net notional volume buy of the Company's open derivative transactions broken out by commodity: Total Volume June 30, 2018 December 31, 2017 Commodity Units (In millions) Natural Gas MMBtu 1 2 Interest Dollars $ 1,972 $ 2,050 Fair Value of Derivative Instruments The following table summarizes the fair value within the derivative instrument valuation on the balance sheet: Fair Value Derivative Assets (a) Derivative Liabilities June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 (In millions) Derivatives Designated as Cash Flow Hedges: Interest rate contracts current $ 1 $ — $ 1 $ 4 Interest rate contracts long-term 9 1 5 9 Total Derivatives Designated as Cash Flow Hedges 10 1 6 13 Derivatives Not Designated as Cash Flow Hedges: Interest rate contracts current — — 4 13 Interest rate contracts long-term 14 — 7 22 Commodity contracts current — 1 1 1 Total Derivatives Not Designated as Cash Flow Hedges 14 1 12 36 Total Derivatives $ 24 $ 2 $ 18 $ 49 (a) Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of June 30, 2018 and December 31, 2017 . The Company has elected to present derivative assets and liabilities on the balance sheet on a trade-by-trade basis and does not offset amounts at the counterparty master agreement level. As of June 30, 2018 and December 31, 2017 , there was no outstanding collateral paid or received. The following tables summarize the offsetting of derivatives by the counterparty master agreement level as of June 30, 2018 and December 31, 2017 : As of June 30, 2018 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts (a) : (In millions) Derivative liabilities $ (1 ) $ — $ (1 ) Total commodity contracts (1 ) — (1 ) Interest rate contracts: Derivative assets 24 (2 ) 22 Derivative liabilities (17 ) 2 (15 ) Total interest rate contracts 7 — 7 Total derivative instruments $ 6 $ — $ 6 (a) There were no commodity contracts classified as derivative assets as of June 30, 2018 . As of December 31, 2017 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts: (In millions) Derivative assets $ 1 $ — $ 1 Derivative liabilities (1 ) — (1 ) Total commodity contracts — — — Interest rate contracts: Derivative assets 1 (1 ) — Derivative liabilities (48 ) 1 (47 ) Total interest rate contracts (47 ) — (47 ) Total derivative instruments $ (47 ) $ — $ (47 ) Accumulated Other Comprehensive Loss The following table summarizes the effects on the Company’s accumulated OCL balance attributable to interest rate swaps designated as cash flow hedge derivatives, net of tax: Three months ended June 30, Six months ended June 30, 2018 2017 2018 2017 (In millions) Accumulated OCL beginning balance $ (43 ) $ (64 ) $ (60 ) $ (70 ) Reclassified from accumulated OCL to income due to realization of previously deferred amounts 2 2 6 6 Mark-to-market of cash flow hedge accounting contracts 5 (8 ) 18 (6 ) Accumulated OCL ending balance, net of income tax benefit of $6 and $16, respectively (36 ) (70 ) (36 ) (70 ) Accumulated OCL attributable to noncontrolling interests (19 ) (42 ) (19 ) (42 ) Accumulated OCL attributable to NRG Yield, Inc. $ (17 ) $ (28 ) $ (17 ) $ (28 ) Losses expected to be realized from OCL during the next 12 months, net of income tax benefit of $1 $ 9 $ 9 The Company's regression analysis for Marsh Landing, Walnut Creek and Avra Valley interest rate swaps, while positively correlated, no longer contain matching terms for cash flow hedge accounting. As a result, the Company voluntarily de-designated the Marsh Landing, Walnut Creek and Avra Valley cash flow hedges as of April 28, 2017, and will prospectively mark these derivatives to market through the income statement. Impact of Derivative Instruments on the Statements of Operations The Company has interest rate derivative instruments that are not designated as cash flow hedges. The effect of interest rate hedges is recorded to interest expense. For the three months ended June 30, 2018 and 2017 , the impact to the consolidated statements of income was a gain of $7 million and a loss of $13 million , respectively. For the six months ended June 30, 2018 and 2017 , the impact to the consolidated statements of operations was a gain of $31 million and a loss of $9 million , respectively. A portion of the Company’s derivative commodity contracts relates to its Thermal Business for the purchase of fuel commodities based on the forecasted usage of the thermal district energy centers. Realized gains and losses on these contracts are reflected in the fuel costs that are permitted to be billed to customers through the related customer contracts or tariffs and, accordingly, no gains or losses are reflected in the consolidated statements of income for these contracts. See Note 5 , Fair Value of Financial Instruments , for a discussion regarding concentration of credit risk.

Long-term Debt

Long-term Debt	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt This footnote should be read in conjunction with the complete description under Note 10 , Long-term Debt , to the consolidated financial statements included in the Company's 2017 Form 10-K. Long-term debt consisted of the following: June 30, 2018 December 31, 2017 June 30, 2018, interest rate % (a) Letters of Credit Outstanding at June 30, 2018 (In millions, except rates) 2019 Convertible Notes $ 345 $ 345 3.500 $ — 2020 Convertible Notes 288 288 3.250 — 2024 Senior Notes 500 500 5.375 — 2026 Senior Notes 350 350 5.000 — NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2023 (b) — 55 L+1.75 67 Project-level debt: Agua Caliente Borrower 2, due 2038 40 41 5.430 17 Alpine, due 2022 133 135 L+1.750 16 Alta Wind I - V lease financing arrangements, due 2034 and 2035 901 926 5.696 - 7.015 102 Buckthorn Solar, due 2025 132 169 L+1.750 16 CVSR, due 2037 731 746 2.339 - 3.775 — CVSR Holdco Notes, due 2037 188 194 4.680 13 El Segundo Energy Center, due 2023 369 400 L+1.75 - L+2.375 138 Energy Center Minneapolis Series C Notes, due 2025 — 83 5.950 — Energy Center Minneapolis Series D Notes, due 2031 125 125 3.550 — Energy Center Minneapolis Series E, F, G, H Notes 203 — various — Laredo Ridge, due 2028 92 95 L+1.875 10 Marsh Landing, due 2023 305 318 L+2.125 65 Tapestry, due 2021 155 162 L+1.625 20 Utah Solar Portfolio, due 2022 273 278 various 13 Viento, due 2023 154 163 L+3.00 26 Walnut Creek, due 2023 254 267 L+1.625 93 Other 432 443 various 36 Subtotal project-level debt: 4,487 4,545 Total debt 5,970 6,083 Less current maturities (c) (651 ) (339 ) Less net debt issuance costs (62 ) (68 ) Less discounts (d) (13 ) (17 ) Total long-term debt $ 5,244 $ 5,659 (a) As of June 30, 2018 , L+ equals 3 month LIBOR plus x%, except for Viento, due 2023 where L+ equals 6 month LIBOR plus 3.00% and Buckthorn Solar and Utah Solar Portfolio, where L+ equals 1 month LIBOR plus x%. (b) Applicable rate is determined by the borrower leverage ratio, as defined in the credit agreement. (c) The 2019 Convertible Notes become due in February 2019 and are included in current portion of long-term debt on the Company's consolidated balance sheet as of June 30, 2018 . Upon conversion of the 2019 Convertible Notes, pursuant to a notice delivered by the Company to the holders of the 2019 Convertible Notes on July 26, 2018, the Company will settle all conversions through the payment of cash, as described in the 2019 Convertible Notes indenture. (d) Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes. The financing arrangements listed above contain certain covenants, including financial covenants that the Company is required to be in compliance with during the term of the respective arrangement. As of June 30, 2018 , the Company was in compliance with all of the required covenants. The discussion below describes material changes to or additions of long-term debt for the six months ended June 30, 2018 . NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility As of June 30, 2018 , there were no outstanding borrowings under the revolving credit facility and the Company had $67 million of letters of credit outstanding. On April 30, 2018, the Company closed on the refinancing of the revolving credit facility, which extended the maturity of the facility to April 28, 2023, and decreased the Company's overall cost of borrowing from L+ 2.50% to L+ 1.75% . The facility will continue to be used for general corporate purposes including financing of future acquisitions and posting letters of credit. On February 6, 2018, NRG Yield Operating LLC and NRG Yield LLC amended the revolving credit facility to modify the "change of control" provisions to permit the consummation of the NRG Transaction, and also to permit NRG Yield Operating LLC, NRG Yield LLC and certain subsidiaries to incur up to $1.5 billion of unsecured indebtedness in order to repurchase or make other required cash payments, in each case if applicable, with respect to NRG Yield Operating LLC’s outstanding senior notes and NRG Yield's outstanding convertible notes in connection with the NRG Transaction. Project - level Debt Energy Center Minneapolis Series E, F, G, H Notes On June 19, 2018, NRG Energy Center Minneapolis LLC, a subsidiary of the Company, entered into an amended and restated Thermal note purchase and private shelf agreement under which it authorized the issuance of the Series E Notes, Series F Notes, Series G Notes, and Series H Notes, as further described in the table below: (in millions) Amount Interest Rate Energy Center Minneapolis Series E Notes, due 2033 $ 70 4.80 % Energy Center Minneapolis Series F Notes, due 2033 10 4.60 % Energy Center Minneapolis Series G Notes, due 2035 83 5.90 % Energy Center Minneapolis Series H Notes, due 2037 40 4.83 % Total proceeds $ 203 Repayment of Energy Center Minneapolis Series C Notes, due 2025 (83 ) 5.95 % Net borrowings $ 120 The proceeds from the sale of the Series E Notes and the Series F Notes were utilized to finance the acquisition of the UPMC Thermal Project as described in Note 3 , Business Acquisitions . The Series G Notes were used to refinance the Series C Notes as noted above in the table. The Series H Notes were used to make a dividend to NRG Yield Operating LLC. The amended and restated Thermal note purchase and private shelf agreement also established a private shelf facility for the future issuance of notes in the amount of $40 million . Buckthorn Solar Drop Down Asset Debt As part of the Buckthorn Solar Drop Down Asset acquisition, as further described in Note 3 , Business Acquisitions , the Company assumed non-recourse debt of $183 million relating to Buckthorn Solar Portfolio, LLC as of the date of the acquisition, March 30, 2018. The assumed debt consisted of a Construction Loan and an Investment Tax Credits, or ITC, Bridge Loan, both at an interest rate of LIBOR plus 1.75% . On May 31, 2018, $132 million of non-recourse debt was converted to a term loan with an expected maturity of May 2025, and the remainder of the non-recourse debt was repaid with the final proceeds from the Class A member upon the project reaching substantial completion in May 2018. Buckthorn Solar entered into a series of fixed for floating interest rate swaps that would fix the interest rate for a minimum of 80% of the outstanding notional amount. All interest rate swap payments by Buckthorn Solar and its counterparties are made quarterly and LIBOR is determined in advance of each interest period.

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic earnings per common share is computed by dividing net income by the weighted average number of common shares outstanding. Shares issued during the year are weighted for the portion of the year that they were outstanding. Diluted earnings per share is computed in a manner consistent with that of basic earnings per share while giving effect to all potentially dilutive common shares that were outstanding during the period. The reconciliation of the Company's basic and diluted earnings per share is shown in the following tables: Three months ended June 30, 2018 2017 (In millions, except per share data) (a) Common Class A Common Class C Common Class A Common Class C Basic earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 27 $ 52 $ 10 $ 18 Weighted average number of common shares outstanding — basic 35 67 35 63 Earnings per weighted average common share — basic $ 0.77 $ 0.77 $ 0.29 $ 0.29 Diluted earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 30 $ 55 $ 13 $ 21 Weighted average number of common shares outstanding — diluted 49 78 49 74 Earnings per weighted average common share — diluted $ 0.61 $ 0.70 $ 0.26 $ 0.28 Six months ended June 30, 2018 2017 (In millions, except per share data) (a) Common Class A Common Class C Common Class A Common Class C Basic earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 33 $ 62 $ 9 $ 16 Weighted average number of common shares outstanding — basic 35 66 35 63 Earnings per weighted average common share — basic $ 0.94 $ 0.94 $ 0.26 $ 0.26 Diluted earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 40 $ 68 $ 9 $ 16 Weighted average number of common shares outstanding — diluted 49 77 35 63 Earnings per weighted average common share — diluted $ 0.80 $ 0.89 $ 0.26 $ 0.26 (a) Basic and diluted earnings per share might not recalculate due to presenting values in millions rather than whole dollars. The following table summarizes the Company's outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company's diluted earnings per share: Three months ended June 30, Six months ended June 30, 2018 2017 2018 2017 (In millions of shares) 2019 Convertible Notes - Common Class A — — — 15 2020 Convertible Notes - Common Class C — — — 10

Changes in Capital Structure

Changes in Capital Structure	6 Months Ended
	Jun. 30, 2018
Changes in Capital Structure [Abstract]
Partners' Capital Notes Disclosure [Text Block]	Changes in Capital Structure At-the-Market Equity Offering Program, or the ATM Program NRG Yield, Inc. is party to an equity distribution agreement with Barclays Capital Inc., Credit Suisse Securities (USA) LLC, J.P. Morgan Securities LLC and RBC Capital Markets, LLC, as sales agents. Pursuant to the terms of the equity distribution agreement, NRG Yield, Inc. may offer and sell shares of its Class C common stock par value $0.01 per share, from time to time through the sales agents up to an aggregate sales price of $150 million through an at-the-market equity offering program, or the ATM Program. NRG Yield, Inc. may also sell shares of its Class C common stock to any of the sales agents, as principals for its own account, at a price agreed upon at the time of sale. The Company sold a total of 4,392,583 shares of Class C common stock for gross proceeds of $77 million during the period ended June 30, 2018 , $1 million of which was received in July of 2018. The Company incurred commission fees of $762 thousand during the period ended June 30, 2018 . As of July 3, 2018, approximately $38 million of Class C common stock remains available for issuance under the ATM Program. As a result of the Company's sale of shares of Class C common stock under the ATM Program, the public shareholders of Class A and Class C common stock increased their economic and voting interests in NRG Yield, Inc. to 54.8% , and 45.0% , respectively, as of June 30, 2018 . Dividends to Class A and Class C common stockholders The following table lists the dividends paid on the Company's Class A common stock and Class C common stock during the six months ended June 30, 2018 : Second Quarter 2018 First Quarter 2018 Dividends per Class A share $ 0.309 $ 0.298 Dividends per Class C share $ 0.309 $ 0.298 Dividends on the Class A common stock and Class C common stock are subject to available capital, market conditions, and compliance with associated laws, regulations and other contractual obligations. The Company expects that, based on current circumstances, comparable cash dividends will continue to be paid in the foreseeable future. On July 24, 2018 , the Company declared quarterly dividends on its Class A common stock and Class C common stock of $0.320 per share payable on September 18, 2018 , to stockholders of record as of September 4, 2018 . The Company also has authorized 10 million shares of preferred stock, par value $0.01 per share. None of the shares of preferred stock have been issued.

Segment Reporting

Segment Reporting	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company’s segment structure reflects how management currently operates and allocates resources. The Company's businesses are segregated based on conventional power generation, renewable businesses which consist of solar and wind, and the thermal and chilled water business. The Corporate segment reflects the Company's corporate costs. The Company's chief operating decision maker, its Chief Executive Officer, evaluates the performance of its segments based on operational measures including adjusted earnings before interest, taxes, depreciation and amortization, or Adjusted EBITDA, and CAFD, as well as economic gross margin and net income (loss). Three months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 85 $ 177 $ 45 $ — $ 307 Cost of operations 10 33 31 — 74 Depreciation and amortization 24 52 6 — 82 General and administrative — — — 6 6 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 51 92 8 (7 ) 144 Equity in earnings of unconsolidated affiliates 2 27 — — 29 Other income, net 1 — — — 1 Interest expense (13 ) (35 ) (2 ) (21 ) (71 ) Income (loss) before income taxes 41 84 6 (28 ) 103 Income tax expense — — — 7 7 Net Income (Loss) $ 41 $ 84 $ 6 $ (35 ) $ 96 Total Assets $ 1,828 $ 5,937 $ 512 $ 171 $ 8,448 Three months ended June 30, 2017 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 83 $ 165 $ 40 $ — $ 288 Cost of operations 15 35 27 — 77 Depreciation and amortization 26 48 5 — 79 General and administrative — — — 6 6 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 42 82 8 (7 ) 125 Equity in earnings of unconsolidated affiliates 3 13 — — 16 Other income, net — — — 1 1 Interest expense (14 ) (53 ) (2 ) (21 ) (90 ) Income (loss) before income taxes 31 42 6 (27 ) 52 Income tax expense — — — 8 8 Net Income (Loss) $ 31 $ 42 $ 6 $ (35 ) $ 44 Six months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 164 $ 275 $ 93 $ — $ 532 Cost of operations 32 67 64 — 163 Depreciation and amortization 50 102 11 — 163 General and administrative — — — 11 11 Acquisition-related transaction and integration costs — — — 2 2 Operating income (loss) 82 106 18 (13 ) 193 Equity in earnings of unconsolidated affiliates 5 28 — — 33 Other income, net 1 1 — — 2 Interest expense (20 ) (59 ) (4 ) (43 ) (126 ) Income (loss) before income taxes 68 76 14 (56 ) 102 Income tax expense — — — 6 6 Net Income (Loss) $ 68 $ 76 $ 14 $ (62 ) $ 96 Total Assets $ 1,828 $ 5,937 $ 512 $ 171 $ 8,448 Six months ended June 30, 2017 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 158 $ 267 $ 84 $ — $ 509 Cost of operations 37 68 57 — 162 Depreciation and amortization 50 96 10 — 156 General and administrative — — — 10 10 Acquisition-related transaction and integration costs — — — 2 2 Operating income (loss) 71 103 17 (12 ) 179 Equity in earnings of unconsolidated affiliates 6 29 — — 35 Other income, net — 1 — 1 2 Loss on debt extinguishment — (2 ) — — (2 ) Interest expense (26 ) (92 ) (5 ) (42 ) (165 ) Income (loss) before income taxes 51 39 12 (53 ) 49 Income tax expense — — — 7 7 Net Income (Loss) $ 51 $ 39 $ 12 $ (60 ) $ 42

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Effective Tax Rate The income tax provision consisted of the following: Three months ended June 30, Six months ended June 30, 2018 2017 2018 2017 (In millions, except percentages) (In millions, except percentages) Income before income taxes $ 103 $ 52 $ 102 $ 49 Income tax expense 7 8 6 7 Effective income tax rate 6.8 % 15.4 % 5.9 % 14.3 % For the three and six months ended June 30, 2018 and 2017 , the overall effective tax rate was different than the statutory rate of 21% and 35% , respectively, primarily due to production and investment tax credits generated from certain wind and solar assets, respectively, and earnings allocated to NRG resulting from its interest in NRG Yield LLC. For tax purposes, NRG Yield LLC is treated as a partnership; therefore, the Company and NRG each record their respective share of taxable income or loss.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions Disclosure	Related Party Transactions In addition to the transactions and relationships described elsewhere in the notes to the consolidated financial statements, NRG or certain subsidiaries of NRG provide services to the Company's project entities. Amounts due to NRG or its subsidiaries are recorded as accounts payable - affiliate and amounts due to the Company from NRG subsidiaries are recorded as accounts receivable - affiliate on the Company's consolidated balance sheet. The disclosures below summarize the Company's material related party transactions with NRG and its subsidiaries that are included in the Company's operating revenues and operating costs. Power Purchase Agreements (PPAs) between the Company and NRG Power Marketing Elbow Creek and Dover are parties to PPAs with NRG Power Marketing and generate revenue under the PPAs, which are recorded to operating revenues in the Company's consolidated statements of operations. For the three and six months ended June 30, 2018 , Elbow Creek and Dover, collectively, generated revenues of $3 million and $6 million , respectively. For the three and six months ended June 30, 2017 , Elbow Creek and Dover, collectively, generated revenue of $3 million and $7 million , respectively. Energy Marketing Services Agreement by and between Thermal entities and NRG Power Marketing NRG Energy Center Dover LLC, NRG Energy Center Minneapolis, NRG Energy Center Phoenix LLC, and NRG Energy Center Paxton LLC, or Thermal entities, which are subsidiaries of the Company, are parties to Energy Marketing Services Agreements with NRG Power Marketing, a wholly-owned subsidiary of NRG. Under the agreements, NRG Power Marketing procures fuel and fuel transportation for the operation of the Thermal entities. For each of the three and six months ended June 30, 2018 and 2017 , the Thermal entities purchased $2 million and $6 million for each period in each year, respectively, of natural gas from NRG Power Marketing. Operation and Maintenance (O&M) Services Agreements by and between the Company's subsidiaries and NRG Certain of the Company's subsidiaries are party to O&M Services Agreements with NRG, pursuant to which NRG subsidiaries provide necessary and appropriate services to operate and maintain the subsidiaries' plant operations, businesses and thermal facilities. NRG is reimbursed for the provided services, as well as for all reasonable and related expenses and expenditures, and payments to third parties for services and materials rendered to or on behalf of the parties to the agreements. NRG is not entitled to any management fee or mark-up under the agreements. The fees incurred under these agreements were $10 million and $20 million for each of the three and six months ended June 30, 2018 , respectively. For the three and six months ended June 30, 2017 , the fees incurred were $9 million and $19 million , respectively. The Company had $9 million and $13 million due to NRG for the services performed under the O&M Agreements in accounts payable — affiliate as of June 30, 2018 and December 31, 2017 , respectively. O&M Services Agreements by and between GenConn and NRG GenConn incurs fees under two O&M agreements with wholly-owned subsidiaries of NRG. For the three and six months ended June 30, 2018 and 2017 , the aggregate fees incurred under the agreements were $2 million and $3 million for each period in each year, respectively. Administrative Services Agreement by and between Marsh Landing and NRG West Coast LLC Marsh Landing is a party to an administrative services agreement with NRG West Coast LLC, a wholly owned subsidiary of NRG. The Company reimbursed costs under this agreement of $6 million and $9 million for each of the three and six months ended June 30, 2018 , respectively. The Company reimbursed costs under the agreement of $3 million and $6 million for the three and six months ended June 30, 2017 , respectively. There was a balance of $1 million due to NRG West Coast LLC in accounts payable—affiliate as of June 30, 2018 and December 31, 2017 . Administrative Services Agreements by and between the Company and NRG Renew Operation & Maintenance LLC Various wholly-owned subsidiaries of the Company in the Renewables segment are party to administrative services agreements with NRG Renew Operation & Maintenance LLC, or RENOM, a wholly-owned subsidiary of NRG, which provides O&M services to these subsidiaries. The Company incurred total expenses for these services of $8 million and $15 million for the three and six months ended June 30, 2018 , respectively. The Company incurred total expenses for these services of $6 million and $12 million for the three and six months ended June 30, 2017 , respectively. There was a balance of $4 million and $5 million due to RENOM as of June 30, 2018 and December 31, 2017 , respectively. Management Services Agreement by and between the Company and NRG NRG provides the Company with various operational, management, and administrative services, which include human resources, accounting, tax, legal, information systems, treasury, and risk management, as set forth in the Management Services Agreement. As of June 30, 2018 , the base management fee was approximately $9 million per year, subject to an inflation-based adjustment annually at an inflation factor based on the year-over-year U.S. consumer price index. The fee is also subject to adjustments following the consummation of future acquisitions and as a result of a change in the scope of services provided under the Management Services Agreement. Costs incurred under this agreement were $3 million and $5 million for the three and six months ended June 30, 2018 , respectively. Costs incurred under this agreement for the three and six months ended June 30, 2017 were $4 million and $6 million , respectively. The costs incurred under the Management Services Agreement included certain direct expenses incurred by NRG on behalf of the Company in addition to the base management fee. EPC Agreement by and between NECP and NRG NRG Business Services LLC, a subsidiary of NRG, and NECP, a wholly owned subsidiary of the Company, entered into an EPC agreement for the construction of a 73 MWt district energy system for NECP to provide 150 kpph of steam, 6,750 tons of chilled water and 7.5 MW of emergency backup power service to UPMC Mercy. The initial term of the energy services agreement with UPMC Mercy will be for a period of twenty years from the service commencement date. On June 19, 2018, as discussed in Note 3 , Business Acquisitions , NECP purchased the UPMC Thermal Project assets from NRG Business Services LLC for cash consideration of $84 million , subject to working capital adjustments. The Company also recorded a payable of $4 million to be paid to NRG upon final completion of the project, which is included in accounts payable - affiliate as of June 30, 2018 .

Contingencies (Notes)

Contingencies (Notes)	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies Disclosure [Text Block]	Contingencies This note should be read in conjunction with the complete description under Note 16 , Commitments and Contingencies , to the Company's 2017 Form 10-K. The Company's material legal proceedings are described below. The Company believes that it has valid defenses to these legal proceedings and intends to defend them vigorously. The Company records reserves for estimated losses from contingencies when information available indicates that a loss is probable and the amount of the loss, or range of loss, can be reasonably estimated. As applicable, the Company has established an adequate reserve for the matters discussed below. In addition, legal costs are expensed as incurred. Management assesses such matters based on current information and makes a judgment concerning its potential outcome, considering the nature of the claim, the amount and nature of damages sought, and the probability of success. The Company is unable to predict the outcome of the legal proceedings below or reasonably estimate the scope or amount of any associated costs and potential liabilities. As additional information becomes available, management adjusts its assessment and estimates of such contingencies accordingly. Because litigation is subject to inherent uncertainties and unfavorable rulings or developments, it is possible that the ultimate resolution of the Company's liabilities and contingencies could be at amounts that are different from its currently recorded reserves and that such difference could be material. In addition to the legal proceedings noted below, the Company and its subsidiaries are party to other litigation or legal proceedings arising in the ordinary course of business. In management's opinion, the disposition of these ordinary course matters will not materially adversely affect the Company's consolidated financial position, results of operations, or cash flows. Braun v. NRG Yield, Inc. — On April 19, 2016, plaintiffs filed a putative class action lawsuit against NRG Yield, Inc., the current and former members of its board of directors individually, and other parties in California Superior Court in Kern County, California. Plaintiffs allege various violations of the Securities Act due to the defendants’ alleged failure to disclose material facts related to low wind production prior to the NRG Yield, Inc.'s June 22, 2015 Class C common stock offering. Plaintiffs seek compensatory damages, rescission, attorney’s fees and costs. The defendants filed demurrers and a motion challenging jurisdiction on October 18, 2016. On July 30, 2018, the plaintiffs filed an opposition to the defendants’ motion to quash service of the summons and an opposition to the defendants’ demurrer. GenOn Noteholders' Lawsuit — On December 13, 2016, certain indenture trustees for an ad hoc group of holders, or the Noteholders, of the GenOn Energy, Inc., or GenOn, 7.875% Senior Notes due 2017, 9.500% Notes due 2018, and 9.875% Notes due 2020, and the GenOn Americas Generation, LLC 8.50% Senior Notes due 2021 and 9.125% Senior Notes due 2031, along with certain of the Noteholders, filed a complaint in the Superior Court of the State of Delaware against NRG and GenOn alleging certain claims related to the Services Agreement between NRG and GenOn. On April 30, 2017, the Noteholders filed an amended complaint that asserts additional claims of fraudulent transfer, insider preference and breach of fiduciary duties. In addition to NRG and GenOn, the amended complaint names NRG Yield LLC and certain current and former officers and directors of GenOn as defendants. The plaintiffs, among other things, generally seek return of all monies paid under the Services Agreement and any other damages that the court deems appropriate. On April 28, 2017, the bondholders filed an amended complaint adding the GenOn directors and officers as defendants and asserting claims that they breached certain fiduciary duties. Plaintiffs specifically allege that the transfer of Marsh Landing to NRG Yield LLC constituted a fraudulent transfer. On June 12, 2017, certain GenOn entities, NRG and certain holders of the GenOn and GenOn Americas Generation, LLC senior notes entered into a restructuring support and lock-up agreement. On July 13, 2018, NRG and GenOn executed a term sheet that resolves and releases the GenOn Noteholder litigation.

Summary of Significant Accoun21

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606, Revenue from Contracts with Customers, or Topic 606, using the modified retrospective method applied to contracts which were not completed as of the adoption date, with no adjustment required to the financial statements upon adoption. Following the adoption of the new standard, the Company’s revenue recognition of its contracts with customers remains materially consistent with its historical practice. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company's policies with respect to its various revenue streams are detailed below. In general, the Company applies the invoicing practical expedient to recognize revenue for the revenue streams detailed below, except in circumstances where the invoiced amount does not represent the value transferred to the customer. Thermal Revenues Steam and chilled water revenue is recognized as the Company transfers the product to the customer, based on customer usage as determined by meter readings taken at month-end. Some locations read customer meters throughout the month, and recognize estimated revenue for the period between meter read date and month-end. For thermal contracts, the Company’s performance obligation to deliver steam and chilled water is satisfied over time and revenue is recognized based on the invoiced amount. The Thermal Business subsidiaries collect and remit state and local taxes associated with sales to their customers, as required by governmental authorities. These taxes are presented on a net basis in the income statement. As contracts for steam and chilled water are long-term contracts, the Company has performance obligations under these contracts that have not yet been satisfied. These performance obligations have transaction prices that are both fixed and variable, and that vary based on the contract duration, customer type, inception date and other contract-specific factors. For the fixed price contracts, the Company cannot accurately estimate the amount of its unsatisfied performance obligations as it will vary based on customer usage, which will depend on factors such as weather and customer activity. Power Purchase Agreements, or PPAs The majority of the Company’s revenues are obtained through PPAs or other contractual agreements. Energy, capacity and where applicable, renewable attributes, from the majority of the Company’s renewable energy assets and certain conventional energy plants is sold through long-term PPAs and tolling agreements to a single counterparty, which is often a utility or commercial customer. The majority of these PPAs are accounted for as leases. ASC 840 requires the minimum lease payments received to be amortized over the term of the lease and contingent rentals are recorded when the achievement of the contingency becomes probable. Judgment is required by management in determining the economic life of each generating facility, in evaluating whether certain lease provisions constitute minimum payments or represent contingent rent and other factors in determining whether a contract contains a lease and whether the lease is an operating lease or capital lease. Renewable Energy Credits, or RECs As stated above, renewable energy credits, or RECs, are usually sold through long-term PPAs. Revenue from the sale of self-generated RECs is recognized when related energy is generated and simultaneously delivered even in cases where there is a certification lag as it has been deemed to be perfunctory. In a bundled contract to sell energy, capacity and/or self-generated RECs, all performance obligations are deemed to be delivered at the same time and hence, timing of recognition of revenue for all performance obligations is the same and occurs over time. In such cases, it is often unnecessary to allocate transaction price to multiple performance obligations. Sale of Emission Allowances The Company records its bank of emission allowances as part of intangible assets. From time to time, management may authorize the transfer of emission allowances in excess of usage from the Company's emission bank to intangible assets held-for-sale for trading purposes. The Company records the sale of emission allowances on a net basis within operating revenue in the Company's consolidated statements of operations. Disaggregated Revenues The following tables represent the Company’s disaggregation of revenue from contracts with customers for the three and six months ended June 30, 2018 , along with the reportable segment for each category: Three months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Total Energy revenue (a) $ 2 $ 193 $ 43 $ 238 Capacity revenue (a) 85 — 2 87 Contract amortization (2 ) (16 ) — (18 ) Total operating revenue 85 177 45 307 Less: Lease revenue (87 ) (179 ) (1 ) (267 ) Less: Contract amortization 2 16 — 18 Total revenue from contracts with customers $ — $ 14 $ 44 $ 58 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 2 $ 179 $ 1 $ 182 Capacity Revenue 85 — — 85 87 179 1 267 Six months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Total Energy revenue (b) $ 3 $ 306 $ 89 $ 398 Capacity revenue (b) 164 — 5 169 Contract amortization (3 ) (31 ) (1 ) (35 ) Total operating revenue 164 275 93 532 Less: Lease revenue (167 ) (280 ) (1 ) (448 ) Less: Contract amortization 3 31 1 35 Total revenue from contracts with customers $ — $ 26 $ 93 $ 119 (b) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 3 $ 280 $ 1 $ 284 Capacity Revenue 164 — — 164 167 280 1 448 Contract Amortization Assets and liabilities recognized from power sales agreements assumed through acquisitions related to the sale of electric capacity and energy in future periods for which the fair value has been determined to be significantly less (more) than market are amortized to revenue over the term of each underlying contract based on actual generation and/or contracted volumes or on a straight-line basis, where applicable. Contract Balances The following table reflects the contract assets and liabilities included on the Company’s balance sheet as of June 30, 2018 : (In millions) June 30, 2018 Accounts receivable, net - Contracts with customers $ 29 Accounts receivable, net - Leases 103 Total accounts receivable, net $ 132
Income Tax, Policy [Policy Text Block]	Income Taxes NRG Yield, Inc. is included in certain NRG consolidated unitary state tax return filings which is reflected in NRG Yield, Inc.'s state effective tax rate. If NRG Yield, Inc. filed under a separate standalone methodology, there would be an additional state tax expense of approximately $2 million as of June 30, 2018 due to a change in the NRG Yield, Inc. state effective tax rate.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions. These estimates and assumptions impact the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could be different from these estimates.
Noncontrolling Interest Disclosure [Text Block]	Noncontrolling Interests Stockholders' equity represents the equity associated with the Class A and Class C common stockholders, the equity associated with the Class B and Class D common stockholder, NRG, and the third-party interests under certain tax equity arrangements are classified as noncontrolling interests. The following table reflects the changes in the Company's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 as previously reported (a) $ 391 Net Assets of Buckthorn Solar Drop Down Asset as of December 31, 2017 21 Balance as of December 31, 2017 as recast $ 412 Capital contributions from tax equity investors, net of distributions 109 Payment for the Buckthorn Solar Drop Down Asset (42 ) Non cash distributions to NRG in connection with the UPMC Thermal Project Asset Acquisition (13 ) Pre-acquisition net income of the Buckthorn Solar Drop Down Asset 4 Comprehensive income 10 Non-cash adjustment for change in tax basis of assets 2 Distributions to NRG, net (63 ) Balance as of June 30, 2018 $ 419 (a) As previously reported in the Company's Form 10-K for the year ended December 31, 2017. NRG Yield LLC Distributions to NRG The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the six months ended June 30, 2018 : Second Quarter 2018 First Quarter 2018 Distributions per Class B Unit $ 0.309 $ 0.298 Distributions per Class D Unit $ 0.309 $ 0.298 On July 24, 2018 , NRG Yield LLC declared a distribution on its Class A, Class B, Class C and Class D units of $0.320 per unit payable on September 18, 2018 to unit holders of record as of September 4, 2018 .
Distributions [Policy Text Block]	NRG Yield LLC Distributions to NRG The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the six months ended June 30, 2018 : Second Quarter 2018 First Quarter 2018 Distributions per Class B Unit $ 0.309 $ 0.298 Distributions per Class D Unit $ 0.309 $ 0.298 On July 24, 2018 , NRG Yield LLC declared a distribution on its Class A, Class B, Class C and Class D units of $0.320 per unit payable on September 18, 2018 to unit holders of record as of September 4, 2018
Recent Accounting Developments	Recent Accounting Developments - Not Yet Adopted ASU 2016-02 — In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), or Topic 842, with the objective to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and to improve financial reporting by expanding the related disclosures. The guidance in Topic 842 provides that a lessee that may have previously accounted for a lease as an operating lease under current GAAP should recognize the assets and liabilities that arise from a lease on the balance sheet. In addition, Topic 842 expands the required quantitative and qualitative disclosures with regards to lease arrangements. The Company will adopt the standard effective January 1, 2019 and expects to elect certain of the practical expedients permitted, including the expedient that permits the Company to retain its existing lease assessment and classification. The Company is currently working through an adoption plan and evaluating the anticipated impact on the Company's results of operations, cash flows and financial position. While the Company is currently evaluating the impact the new guidance will have on its financial position and results of operations, the Company expects to recognize lease liabilities and right of use assets. The extent of the increase to assets and liabilities associated with these amounts remains to be determined pending the Company’s review of its existing lease contracts and service contracts which may contain embedded leases. While this review is still in process, the Company believes the adoption of Topic 842 may be material to its financial statements. The Company is continuing to monitor potential changes to Topic 842 that have been proposed by the FASB and will assess any necessary changes to the implementation as the guidance is updated.

Segment Reporting Segment Repor

Segment Reporting Segment Reporting (Policies)	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Segment Reporting, Policy [Policy Text Block]	The Company’s segment structure reflects how management currently operates and allocates resources. The Company's businesses are segregated based on conventional power generation, renewable businesses which consist of solar and wind, and the thermal and chilled water business. The Corporate segment reflects the Company's corporate costs. The Company's chief operating decision maker, its Chief Executive Officer, evaluates the performance of its segments based on operational measures including adjusted earnings before interest, taxes, depreciation and amortization, or Adjusted EBITDA, and CAFD, as well as economic gross margin and net income (loss).

Nature of Business Nature of Bu

Nature of Business Nature of Business (Tables)	6 Months Ended
	Jun. 30, 2018
Nature of Business Disclosure [Abstract]
IPO of NRG Yield	The following table represents the structure of the Company as of June 30, 2018 :
Schedule of Ownership	As of June 30, 2018 , the Company's operating assets are comprised of the following projects: Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Conventional El Segundo 100 % 550 Southern California Edison 2023 GenConn Devon 50 % 95 Connecticut Light & Power 2040 GenConn Middletown 50 % 95 Connecticut Light & Power 2041 Marsh Landing 100 % 720 Pacific Gas and Electric 2023 Walnut Creek 100 % 485 Southern California Edison 2023 1,945 Utility Scale Solar Agua Caliente 16 % 46 Pacific Gas and Electric 2039 Alpine 100 % 66 Pacific Gas and Electric 2033 Avenal 50 % 23 Pacific Gas and Electric 2031 Avra Valley 100 % 26 Tucson Electric Power 2032 Blythe 100 % 21 Southern California Edison 2029 Borrego 100 % 26 San Diego Gas and Electric 2038 CVSR 100 % 250 Pacific Gas and Electric 2038 Desert Sunlight 250 25 % 63 Southern California Edison 2034 Desert Sunlight 300 25 % 75 Pacific Gas and Electric 2039 Kansas South 100 % 20 Pacific Gas and Electric 2033 Roadrunner 100 % 20 El Paso Electric 2031 TA High Desert 100 % 20 Southern California Edison 2033 Utah Solar Portfolio (b) (e) 50 % 265 PacifiCorp 2036 921 Distributed Solar Apple I LLC Projects 100 % 9 Various 2032 AZ DG Solar Projects 100 % 5 Various 2025 - 2033 SPP Projects 100 % 25 Various 2026 - 2037 Other DG Projects 100 % 13 Various 2023 - 2039 52 Wind Alta I 100 % 150 Southern California Edison 2035 Alta II 100 % 150 Southern California Edison 2035 Alta III 100 % 150 Southern California Edison 2035 Alta IV 100 % 102 Southern California Edison 2035 Alta V 100 % 168 Southern California Edison 2035 Alta X (b) 100 % 137 Southern California Edison 2038 Alta XI (b) 100 % 90 Southern California Edison 2038 Buffalo Bear 100 % 19 Western Farmers Electric Co-operative 2033 Crosswinds (b) (f) 99 % 21 Corn Belt Power Cooperative 2027 Elbow Creek (b) (f) 100 % 122 NRG Power Marketing LLC 2022 Elkhorn Ridge (b) (f) 66.7 % 54 Nebraska Public Power District 2029 Forward (b) (f) 100 % 29 Constellation NewEnergy, Inc. 2022 Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Goat Wind (b) (f) 100 % 150 Dow Pipeline Company 2025 Hardin (b) (f) 99 % 15 Interstate Power and Light Company 2027 Laredo Ridge 100 % 80 Nebraska Public Power District 2031 Lookout (b) (f) 100 % 38 Southern Maryland Electric Cooperative 2030 Odin (b) (f) 99.9 % 20 Missouri River Energy Services 2028 Pinnacle 100 % 55 Maryland Department of General Services and University System of Maryland 2031 San Juan Mesa (b) (f) 75 % 90 Southwestern Public Service Company 2025 Sleeping Bear (b) (f) 100 % 95 Public Service Company of Oklahoma 2032 South Trent 100 % 101 AEP Energy Partners 2029 Spanish Fork (b) (f) 100 % 19 PacifiCorp 2028 Spring Canyon II (b) 90.1 % 29 Platte River Power Authority 2039 Spring Canyon III (b) 90.1 % 25 Platte River Power Authority 2039 Taloga 100 % 130 Oklahoma Gas & Electric 2031 Wildorado (b) (f) 100 % 161 Southwestern Public Service Company 2027 2,200 Thermal NRG Energy Center Dover LLC 100 % 103 NRG Power Marketing LLC 2018 Thermal generation 100 % 30 Various Various 133 Total net generation capacity (c) 5,251 Thermal equivalent MWt (d) 100 % 1,392 Various Various (a) Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018 . (b) Projects are part of tax equity arrangements. (c) The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs. (d) For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers. (e) Represents interests in Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC, all acquired as part of the March 2017 Drop Down Assets (ownership percentage is based upon cash to be distributed). (f) Projects are part of NRG Wind TE Holdco portfolio.

Summary of Significant Accoun24

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Schedule of Accumulated Depreciation and Amortization [Table Text Block]	The following table presents the accumulated depreciation included in the property, plant and equipment, net, and accumulated amortization included in intangible assets, net, respectively, as of June 30, 2018 and December 31, 2017 : June 30, 2018 December 31, 2017 (In millions) Property, Plant and Equipment Accumulated Depreciation $ 1,428 $ 1,285 Intangible Assets Accumulated Amortization 272 237
Schedule of Change in Noncontrolling Interest [Table Text Block]	The following table reflects the changes in the Company's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 as previously reported (a) $ 391 Net Assets of Buckthorn Solar Drop Down Asset as of December 31, 2017 21 Balance as of December 31, 2017 as recast $ 412 Capital contributions from tax equity investors, net of distributions 109 Payment for the Buckthorn Solar Drop Down Asset (42 ) Non cash distributions to NRG in connection with the UPMC Thermal Project Asset Acquisition (13 ) Pre-acquisition net income of the Buckthorn Solar Drop Down Asset 4 Comprehensive income 10 Non-cash adjustment for change in tax basis of assets 2 Distributions to NRG, net (63 ) Balance as of June 30, 2018 $ 419
Distributions Made to Limited Liability Company (LLC) Member, by Distribution [Table Text Block]	The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the six months ended June 30, 2018 : Second Quarter 2018 First Quarter 2018 Distributions per Class B Unit $ 0.309 $ 0.298 Distributions per Class D Unit $ 0.309 $ 0.298
Disaggregation of Revenue [Table Text Block]	The following tables represent the Company’s disaggregation of revenue from contracts with customers for the three and six months ended June 30, 2018 , along with the reportable segment for each category: Three months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Total Energy revenue (a) $ 2 $ 193 $ 43 $ 238 Capacity revenue (a) 85 — 2 87 Contract amortization (2 ) (16 ) — (18 ) Total operating revenue 85 177 45 307 Less: Lease revenue (87 ) (179 ) (1 ) (267 ) Less: Contract amortization 2 16 — 18 Total revenue from contracts with customers $ — $ 14 $ 44 $ 58 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 2 $ 179 $ 1 $ 182 Capacity Revenue 85 — — 85 87 179 1 267 Six months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Total Energy revenue (b) $ 3 $ 306 $ 89 $ 398 Capacity revenue (b) 164 — 5 169 Contract amortization (3 ) (31 ) (1 ) (35 ) Total operating revenue 164 275 93 532 Less: Lease revenue (167 ) (280 ) (1 ) (448 ) Less: Contract amortization 3 31 1 35 Total revenue from contracts with customers $ — $ 26 $ 93 $ 119 (b) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 3 $ 280 $ 1 $ 284 Capacity Revenue 164 — — 164 167 280 1 448
Contract with Customer, Asset and Liability [Table Text Block]	The following table reflects the contract assets and liabilities included on the Company’s balance sheet as of June 30, 2018 : (In millions) June 30, 2018 Accounts receivable, net - Contracts with customers $ 29 Accounts receivable, net - Leases 103 Total accounts receivable, net $ 132

Business Acquisitions Busines25

Business Acquisitions Business Acquisitions (Tables)	6 Months Ended
	Jun. 30, 2018
November 2017 Drop Down Assets and August 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information [Table Text Block]	The following tables present a summary of the Company's historical information combining the financial information for the Buckthorn Solar Drop Down Asset, November 2017 Drop Down Assets and August 2017 Drop Down Assets transferred in connection with the acquisition: Three months ended June 30, 2017 As Previously Reported (a) Buckthorn Solar Drop Down Asset November 2017 Drop Down Assets August 2017 Drop Down Assets As Currently Reported (In millions) Total operating revenues $ 284 $ — $ 4 $ — $ 288 Operating income 122 — 3 — 125 Net income (loss) 45 (3 ) 2 — 44 Less: Pre-acquisition net (loss) income of Drop Down Assets — (3 ) 2 3 2 Less: Income (loss) attributable to noncontrolling interests 17 — — (3 ) 14 Net income attributable to NRG Yield, Inc. 28 — — — 28 Six months ended June 30, 2017 As Previously Reported (a) Buckthorn Solar Drop Down Asset November 2017 Drop Down Assets August 2017 Drop Down Assets As Currently Reported (In millions) Total operating revenues $ 502 $ — $ 7 $ — $ 509 Operating income 176 — 3 — 179 Net income (loss) 44 (3 ) 1 — 42 Less: Pre-acquisition net income (loss) of Drop Down Assets 12 (3 ) 1 5 15 Less: Income (loss) attributable to noncontrolling interests 7 — — (5 ) 2 Net income attributable to NRG Yield, Inc. 25 — — — 25 (a) As previously reported in the Company's Form 10-Q for the quarter ended June 30, 2017
Buckthorn Solar Drop Down Asset [Member]
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following is a summary of net assets transferred in connection with the acquisition of the Buckthorn Solar Drop Down Asset as of March 31, 2018: (In millions) Assets: Current assets $ 20 Property, plant and equipment 212 Non-current assets 3 Total assets 235 Liabilities: Debt (Current and non-current) (a) 176 Other current and non-current liabilities 15 Total liabilities 191 Less: noncontrolling interest 19 Net assets acquired $ 25 (a) Net of $7 million of net debt issuance costs.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	6 Months Ended
	Jun. 30, 2018
Entities that are not consolidated [Member]
Schedule of Equity Method Investments [Line Items]
Schedule of Variable Interest Entities [Table Text Block]	The Company's maximum exposure to loss as of June 30, 2018 , is limited to its equity investment in the unconsolidated entities, as further summarized in the table below: (In millions) Maximum exposure to loss Four Brothers Solar, LLC $ 209 GenConn Energy LLC 100 NRG DGPV Holdco 1 LLC 81 Granite Mountain Holdings, LLC 76 NRG DGPV Holdco 3 LLC 75 NRG DGPV Holdco 2 LLC 61 Iron Springs Holdings, LLC 53 NRG RPV Holdco 1 LLC 46
Consolidated Entities [Member]
Schedule of Equity Method Investments [Line Items]
Schedule of Variable Interest Entities [Table Text Block]	Summarized financial information for the Company's consolidated VIEs consisted of the following as of June 30, 2018 : (In millions) NRG Wind TE Holdco Alta Wind TE Holdco Spring Canyon Buckthorn Renewables, LLC Other current and non-current assets $ 163 $ 23 $ 1 $ 24 Property, plant and equipment 362 423 93 226 Intangible assets 2 256 — — Total assets 527 702 94 250 Current and non-current liabilities 184 9 4 141 Total liabilities 184 9 4 141 Noncontrolling interest 10 72 48 48 Net assets less noncontrolling interests $ 333 $ 621 $ 42 $ 61

Fair Value of Financial Instr27

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Estimated carrying values and fair values	The estimated carrying amounts and fair values of the Company’s recorded financial instruments not carried at fair market value are as follows: As of June 30, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable $ 6 $ 6 $ 13 $ 13 Liabilities: Long-term debt, including current portion (a) $ 5,957 $ 5,936 $ 6,066 $ 6,099
Fair Value Option, Disclosures [Table Text Block]	The fair value of the Company's publicly-traded long-term debt is based on quoted market prices and is classified as Level 2 within the fair value hierarchy. The fair value of debt securities, non-publicly traded long-term debt and certain notes receivable of the Company are based on expected future cash flows discounted at market interest rates, or current interest rates for similar instruments with equivalent credit quality and are classified as Level 3 within the fair value hierarchy. The following table presents the level within the fair value hierarchy for long-term debt, including current portion as of June 30, 2018 and December 31, 2017 : As of June 30, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 1,456 $ 4,480 $ 1,502 $ 4,597
Schedule of Fair Value, Assets and Liabilities [Table Text Block]	The Company records its derivative assets and liabilities at fair value on its consolidated balance sheet. The following table presents assets and liabilities measured and recorded at fair value on the Company's consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of June 30, 2018 As of December 31, 2017 Fair Value (a) Fair Value (a) (In millions) Level 2 Level 2 Derivative assets: Commodity contracts $ — $ 1 Interest rate contracts 24 1 Total assets 24 2 Derivative liabilities: Commodity contracts 1 1 Interest rate contracts 17 48 Total liabilities $ 18 $ 49 (a) There were no derivative assets or liabilities classified as Level 1 or Level 3 as of June 30, 2018 and December 31, 2017 .

Accounting for Derivative Ins28

Accounting for Derivative Instruments and Hedging Activities (Tables)	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net notional volume buy/(sell) of NRG Yield's open derivative transactions broken out by commodity	The following table summarizes the net notional volume buy of the Company's open derivative transactions broken out by commodity: Total Volume June 30, 2018 December 31, 2017 Commodity Units (In millions) Natural Gas MMBtu 1 2 Interest Dollars $ 1,972 $ 2,050
Fair value within the derivative instrument valuation on the balance sheets	he following table summarizes the fair value within the derivative instrument valuation on the balance sheet: Fair Value Derivative Assets (a) Derivative Liabilities June 30, 2018 December 31, 2017 June 30, 2018 December 31, 2017 (In millions) Derivatives Designated as Cash Flow Hedges: Interest rate contracts current $ 1 $ — $ 1 $ 4 Interest rate contracts long-term 9 1 5 9 Total Derivatives Designated as Cash Flow Hedges 10 1 6 13 Derivatives Not Designated as Cash Flow Hedges: Interest rate contracts current — — 4 13 Interest rate contracts long-term 14 — 7 22 Commodity contracts current — 1 1 1 Total Derivatives Not Designated as Cash Flow Hedges 14 1 12 36 Total Derivatives $ 24 $ 2 $ 18 $ 49 (a) Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of June 30, 2018 and December 31, 2017 .
Offsetting of derivatives by counterparty master agreement level and collateral received or paid	The following tables summarize the offsetting of derivatives by the counterparty master agreement level as of June 30, 2018 and December 31, 2017 : As of June 30, 2018 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts (a) : (In millions) Derivative liabilities $ (1 ) $ — $ (1 ) Total commodity contracts (1 ) — (1 ) Interest rate contracts: Derivative assets 24 (2 ) 22 Derivative liabilities (17 ) 2 (15 ) Total interest rate contracts 7 — 7 Total derivative instruments $ 6 $ — $ 6 (a) There were no commodity contracts classified as derivative assets as of June 30, 2018 . As of December 31, 2017 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts: (In millions) Derivative assets $ 1 $ — $ 1 Derivative liabilities (1 ) — (1 ) Total commodity contracts — — — Interest rate contracts: Derivative assets 1 (1 ) — Derivative liabilities (48 ) 1 (47 ) Total interest rate contracts (47 ) — (47 ) Total derivative instruments $ (47 ) $ — $ (47 )
Effects of NRG Yield's accumulated OCI balance attributable to interest rate swaps designated as cash flow hedge derivatives, net of tax	The following table summarizes the effects on the Company’s accumulated OCL balance attributable to interest rate swaps designated as cash flow hedge derivatives, net of tax: Three months ended June 30, Six months ended June 30, 2018 2017 2018 2017 (In millions) Accumulated OCL beginning balance $ (43 ) $ (64 ) $ (60 ) $ (70 ) Reclassified from accumulated OCL to income due to realization of previously deferred amounts 2 2 6 6 Mark-to-market of cash flow hedge accounting contracts 5 (8 ) 18 (6 ) Accumulated OCL ending balance, net of income tax benefit of $6 and $16, respectively (36 ) (70 ) (36 ) (70 ) Accumulated OCL attributable to noncontrolling interests (19 ) (42 ) (19 ) (42 ) Accumulated OCL attributable to NRG Yield, Inc. $ (17 ) $ (28 ) $ (17 ) $ (28 ) Losses expected to be realized from OCL during the next 12 months, net of income tax benefit of $1 $ 9 $ 9

Long-term Debt (Tables)

Long-term Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Instrument [Line Items]
Schedule of long-term debt	Long-term debt consisted of the following: June 30, 2018 December 31, 2017 June 30, 2018, interest rate % (a) Letters of Credit Outstanding at June 30, 2018 (In millions, except rates) 2019 Convertible Notes $ 345 $ 345 3.500 $ — 2020 Convertible Notes 288 288 3.250 — 2024 Senior Notes 500 500 5.375 — 2026 Senior Notes 350 350 5.000 — NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2023 (b) — 55 L+1.75 67 Project-level debt: Agua Caliente Borrower 2, due 2038 40 41 5.430 17 Alpine, due 2022 133 135 L+1.750 16 Alta Wind I - V lease financing arrangements, due 2034 and 2035 901 926 5.696 - 7.015 102 Buckthorn Solar, due 2025 132 169 L+1.750 16 CVSR, due 2037 731 746 2.339 - 3.775 — CVSR Holdco Notes, due 2037 188 194 4.680 13 El Segundo Energy Center, due 2023 369 400 L+1.75 - L+2.375 138 Energy Center Minneapolis Series C Notes, due 2025 — 83 5.950 — Energy Center Minneapolis Series D Notes, due 2031 125 125 3.550 — Energy Center Minneapolis Series E, F, G, H Notes 203 — various — Laredo Ridge, due 2028 92 95 L+1.875 10 Marsh Landing, due 2023 305 318 L+2.125 65 Tapestry, due 2021 155 162 L+1.625 20 Utah Solar Portfolio, due 2022 273 278 various 13 Viento, due 2023 154 163 L+3.00 26 Walnut Creek, due 2023 254 267 L+1.625 93 Other 432 443 various 36 Subtotal project-level debt: 4,487 4,545 Total debt 5,970 6,083 Less current maturities (c) (651 ) (339 ) Less net debt issuance costs (62 ) (68 ) Less discounts (d) (13 ) (17 ) Total long-term debt $ 5,244 $ 5,659 (a) As of June 30, 2018 , L+ equals 3 month LIBOR plus x%, except for Viento, due 2023 where L+ equals 6 month LIBOR plus 3.00% and Buckthorn Solar and Utah Solar Portfolio, where L+ equals 1 month LIBOR plus x%. (b) Applicable rate is determined by the borrower leverage ratio, as defined in the credit agreement. (c) The 2019 Convertible Notes become due in February 2019 and are included in current portion of long-term debt on the Company's consolidated balance sheet as of June 30, 2018 . Upon conversion of the 2019 Convertible Notes, pursuant to a notice delivered by the Company to the holders of the 2019 Convertible Notes on July 26, 2018, the Company will settle all conversions through the payment of cash, as described in the 2019 Convertible Notes indenture. (d) Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes.
NRG Energy Center Minneapolis Series E, F, G, H Notes [Member] [Member]
Debt Instrument [Line Items]
Schedule of Long-term Debt Instruments [Table Text Block]	On June 19, 2018, NRG Energy Center Minneapolis LLC, a subsidiary of the Company, entered into an amended and restated Thermal note purchase and private shelf agreement under which it authorized the issuance of the Series E Notes, Series F Notes, Series G Notes, and Series H Notes, as further described in the table below: (in millions) Amount Interest Rate Energy Center Minneapolis Series E Notes, due 2033 $ 70 4.80 % Energy Center Minneapolis Series F Notes, due 2033 10 4.60 % Energy Center Minneapolis Series G Notes, due 2035 83 5.90 % Energy Center Minneapolis Series H Notes, due 2037 40 4.83 % Total proceeds $ 203 Repayment of Energy Center Minneapolis Series C Notes, due 2025 (83 ) 5.95 % Net borrowings $ 120

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The reconciliation of the Company's basic and diluted earnings per share is shown in the following tables: Three months ended June 30, 2018 2017 (In millions, except per share data) (a) Common Class A Common Class C Common Class A Common Class C Basic earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 27 $ 52 $ 10 $ 18 Weighted average number of common shares outstanding — basic 35 67 35 63 Earnings per weighted average common share — basic $ 0.77 $ 0.77 $ 0.29 $ 0.29 Diluted earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 30 $ 55 $ 13 $ 21 Weighted average number of common shares outstanding — diluted 49 78 49 74 Earnings per weighted average common share — diluted $ 0.61 $ 0.70 $ 0.26 $ 0.28 Six months ended June 30, 2018 2017 (In millions, except per share data) (a) Common Class A Common Class C Common Class A Common Class C Basic earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 33 $ 62 $ 9 $ 16 Weighted average number of common shares outstanding — basic 35 66 35 63 Earnings per weighted average common share — basic $ 0.94 $ 0.94 $ 0.26 $ 0.26 Diluted earnings per share attributable to NRG Yield, Inc. common stockholders Net income attributable to NRG Yield, Inc. $ 40 $ 68 $ 9 $ 16 Weighted average number of common shares outstanding — diluted 49 77 35 63 Earnings per weighted average common share — diluted $ 0.80 $ 0.89 $ 0.26 $ 0.26
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]	The following table summarizes the Company's outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company's diluted earnings per share: Three months ended June 30, Six months ended June 30, 2018 2017 2018 2017 (In millions of shares) 2019 Convertible Notes - Common Class A — — — 15 2020 Convertible Notes - Common Class C — — — 10

Changes in Capital Structure St

Changes in Capital Structure Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2018
Changes in Capital Structure [Abstract]
Dividends Declared [Table Text Block]	The following table lists the dividends paid on the Company's Class A common stock and Class C common stock during the six months ended June 30, 2018 : Second Quarter 2018 First Quarter 2018 Dividends per Class A share $ 0.309 $ 0.298 Dividends per Class C share $ 0.309 $ 0.298

Segment Reporting (Tables)

Segment Reporting (Tables)	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Three months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 85 $ 177 $ 45 $ — $ 307 Cost of operations 10 33 31 — 74 Depreciation and amortization 24 52 6 — 82 General and administrative — — — 6 6 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 51 92 8 (7 ) 144 Equity in earnings of unconsolidated affiliates 2 27 — — 29 Other income, net 1 — — — 1 Interest expense (13 ) (35 ) (2 ) (21 ) (71 ) Income (loss) before income taxes 41 84 6 (28 ) 103 Income tax expense — — — 7 7 Net Income (Loss) $ 41 $ 84 $ 6 $ (35 ) $ 96 Total Assets $ 1,828 $ 5,937 $ 512 $ 171 $ 8,448 Three months ended June 30, 2017 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 83 $ 165 $ 40 $ — $ 288 Cost of operations 15 35 27 — 77 Depreciation and amortization 26 48 5 — 79 General and administrative — — — 6 6 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 42 82 8 (7 ) 125 Equity in earnings of unconsolidated affiliates 3 13 — — 16 Other income, net — — — 1 1 Interest expense (14 ) (53 ) (2 ) (21 ) (90 ) Income (loss) before income taxes 31 42 6 (27 ) 52 Income tax expense — — — 8 8 Net Income (Loss) $ 31 $ 42 $ 6 $ (35 ) $ 44 Six months ended June 30, 2018 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 164 $ 275 $ 93 $ — $ 532 Cost of operations 32 67 64 — 163 Depreciation and amortization 50 102 11 — 163 General and administrative — — — 11 11 Acquisition-related transaction and integration costs — — — 2 2 Operating income (loss) 82 106 18 (13 ) 193 Equity in earnings of unconsolidated affiliates 5 28 — — 33 Other income, net 1 1 — — 2 Interest expense (20 ) (59 ) (4 ) (43 ) (126 ) Income (loss) before income taxes 68 76 14 (56 ) 102 Income tax expense — — — 6 6 Net Income (Loss) $ 68 $ 76 $ 14 $ (62 ) $ 96 Total Assets $ 1,828 $ 5,937 $ 512 $ 171 $ 8,448 Six months ended June 30, 2017 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 158 $ 267 $ 84 $ — $ 509 Cost of operations 37 68 57 — 162 Depreciation and amortization 50 96 10 — 156 General and administrative — — — 10 10 Acquisition-related transaction and integration costs — — — 2 2 Operating income (loss) 71 103 17 (12 ) 179 Equity in earnings of unconsolidated affiliates 6 29 — — 35 Other income, net — 1 — 1 2 Loss on debt extinguishment — (2 ) — — (2 ) Interest expense (26 ) (92 ) (5 ) (42 ) (165 ) Income (loss) before income taxes 51 39 12 (53 ) 49 Income tax expense — — — 7 7 Net Income (Loss) $ 51 $ 39 $ 12 $ (60 ) $ 42

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Reconciliation of the U.S. federal statutory rate to the Company's effective rate	The income tax provision consisted of the following: Three months ended June 30, Six months ended June 30, 2018 2017 2018 2017 (In millions, except percentages) (In millions, except percentages) Income before income taxes $ 103 $ 52 $ 102 $ 49 Income tax expense 7 8 6 7 Effective income tax rate 6.8 % 15.4 % 5.9 % 14.3 %

Nature of Business (Details)

Nature of Business (Details) $ in Millions		Mar. 31, 2018USD ($)	Aug. 02, 2017USD ($)	Mar. 27, 2017USD ($)MW	Jun. 30, 2018USD ($)MW	Mar. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Nature of Business
Weighted Average Remaining PPA Term					15 years
Power Generation Capacity, Megawatts	[1],[2]				5,251
Power Generation Capacity, Megawatts, including portion attributable to noncontrolling interest					5,257
Megawatts Thermal Equivalent, Available Under right-to-use Provisions					134
Long-term Debt | $					$ 5,970		$ 6,083
Conventional Generation, Utility-Scale Solar, Distributed Solar, and Wind [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]				5,118
Conventional Generation [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]				1,945
Utility-Scale Solar
Nature of Business
Power Generation Capacity, Megawatts	[1]				921
Distributed Solar [Member]
Nature of Business
Power Generation Capacity, Megawatts					52
Wind Farms [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]				2,200
Thermal [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				133
Steam and Chilled Water Capacity, Megawatts Thermal Equivalent	[1],[3]				1,392
NRG Energy Center Dover [Member]
Nature of Business
Percentage of Ownership					100.00%
NRG Yield, Inc. [Member]
Nature of Business
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Voting Interest					45.00%
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest					54.80%
NRG Yield LLC | NRG [Member]
Nature of Business
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Voting Interest					55.00%
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest					45.20%
GenConn Middletown | Conventional Generation [Member]
Nature of Business
Equity Method Investment, Ownership Percentage					50.00%
Power Generation Capacity, Megawatts	[1]				95
GenConn Devon [Member] | Conventional Generation [Member]
Nature of Business
Equity Method Investment, Ownership Percentage					50.00%
Power Generation Capacity, Megawatts	[1]				95
Marsh Landing | Conventional Generation [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				720
El Segundo [Member] | Conventional Generation [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				550
Walnut Creek [Member] | Conventional Generation [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				485
Agua Caliente [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					16.00%
Power Generation Capacity, Megawatts	[1]				46
Alpine [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				66
Avenal [Member] | Utility-Scale Solar
Nature of Business
Equity Method Investment, Ownership Percentage					50.00%
Power Generation Capacity, Megawatts	[1]				23
Avra Valley | Utility-Scale Solar
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				26
NRG Solar Blythe LLC [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				21
Borrego [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				26
CVSR [Member] | Utility-Scale Solar
Nature of Business
Equity Method Investment, Ownership Percentage					100.00%
Power Generation Capacity, Megawatts	[1]				250
Desert Sunlight [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					25.00%
Kansas South [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				20
Roadrunner | Utility-Scale Solar
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				20
TA - High Desert LLC [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				20
Utah Portfolio [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership					50.00%
Power Generation Capacity, Megawatts	[1],[4],[5]				265
AZ DG Solar Projects [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts					5
PFMG DG Solar Projects [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts					9
Alta I [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				150
Alta II [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				150
Alta III [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				150
Alta IV [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				102
Alta V [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				168
Alta X [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4]				137
Alta XI [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4]				90
South Trent | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				101
Spanish Fork [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				19
Spring Canyon II [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					90.10%
Power Generation Capacity, Megawatts	[1],[4]				29
Laredo Ridge [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				80
Lookout [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				38
Odin Wind Farm [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					99.90%
Power Generation Capacity, Megawatts	[1],[4],[6]				20
Taloga [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				130
Wildorado [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4]				161
Pinnacle [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				55
San Juan Mesa Wind Project, LLC [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					75.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				90
Sleeping Bear [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				95
Buffalo Bear [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1]				19
Crosswinds [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					99.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				21
Elbow Creek [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				122
Elkhorn Ridge Wind, LLC [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					66.70%
Power Generation Capacity, Megawatts	[1],[4],[6]				54
Forward [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				29
Goat Wind [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				150
Hardin [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					99.00%
Power Generation Capacity, Megawatts	[1],[4],[6]				15
Spring Canyon [Member] | Wind Farms [Member]
Nature of Business
Power Generation Capacity, Megawatts attributed to noncontrolling interest					6
Spring Canyon III [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership					90.10%
Power Generation Capacity, Megawatts	[1],[4]				25
Thermal [Member] | Thermal [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]				30
NRG Energy Center Dover [Member] | Thermal [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]				103
SPP Projects [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts					25
Other DG Assets [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts					13
Buckthorn Solar Drop Down Asset [Member]
Nature of Business
Power Generation Capacity, Megawatts					154
Business Acquisitions, Purchase Price | $		$ 42
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value | $						$ 19
August 2017 Drop Down Assets [Member]
Nature of Business
Business Acquisitions, Purchase Price | $			$ 44
Southern California Edison [Member] | Desert Sunlight [Member] | Utility-Scale Solar
Nature of Business
Power Generation Capacity, Megawatts	[1]				63
Pacific Gas and Electric [Member] | Desert Sunlight [Member] | Utility-Scale Solar
Nature of Business
Power Generation Capacity, Megawatts	[1]				75
Common Class D [Member] | NRG Yield LLC
Nature of Business
Sale of Stock, Percentage of Ownership after Transaction					100.00%
Unconsolidated Solar Partnerships [Member]
Nature of Business
Power Generation Capacity, Megawatts					268
Agua Caliente [Member]
Nature of Business
Long-term Debt | $					$ 812
March 2017 Drop Down Assets [Member]
Nature of Business
Business Acquisitions, Purchase Price | $				$ 128
Agua Caliente Borrower 2 [Member]
Nature of Business
Equity Method Investment, Ownership Percentage					16.00%
Power Generation Capacity, Megawatts				46
Agua Caliente Borrower 2 [Member] | NRG [Member]
Nature of Business
Percentage of Ownership				51.00%
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.
[3]	For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers.
[4]	Projects are part of tax equity arrangements
[5]	Represents interests in Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC, all acquired as part of the March 2017 Drop Down Assets (ownership percentage is based upon cash to be distributed).
[6]	Projects are part of NRG Wind TE Holdco portfolio.

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Millions		May 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017		Dec. 31, 2017
Summary of Significant Accounting Policies [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment			$ 1,428				$ 1,428			$ 1,285
Finite-Lived Intangible Assets, Accumulated Amortization			272				272			237
Stockholders' Equity Attributable to Noncontrolling Interest			(419)				(419)			(412)	[1]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			2,287				2,287			2,159	[1]
Payment of capital distributions and returns of capital, net of capital distributions, non-cash							(13)
Pre-acquisition net income of the Buckthorn Solar Drop Down Asset			0		$ 2	[1]	4	$ 15	[1]
Comprehensive income			21		11	[1]	10	2	[1]
Stockholders' Equity, Other							(2)
Distributions to NRG, net							$ (63)
Dividends Payable, Date Declared							Jul. 24, 2018
Common Stock, Dividends, Per Share, Declared							$ 0.320
Dividends Payable, Date to be Paid							Sep. 18, 2018
Dividends Payable, Date of Record							Sep. 4, 2018
Revenue from Contract with Customer, Excluding Assessed Tax			58				$ 119
Capitalized Contract Cost, Amortization			18				35
Total operating revenues			307		288	[1]	532	509	[1]
Operating Leases, Income Statement, Contingent Revenue			(267)				(448)
Accounts Receivable, Net			$ 132				132
Buckthorn Solar Drop Down Asset [Member]
Summary of Significant Accounting Policies [Line Items]
Payment for the Buckthorn Solar Drop Down Asset							(42)
Pre-acquisition net income of the Buckthorn Solar Drop Down Asset					(3)			(3)
Total operating revenues					0			0
Financial Institutions [Member]
Summary of Significant Accounting Policies [Line Items]
Capital contributions from tax equity investors, net of distributions							109
Common Class B [Member]
Summary of Significant Accounting Policies [Line Items]
Distribution Made to Limited Liability Company (LLC) Member, Distributions Paid, Per Unit			$ 0.309	$ 0.298
Common Class D [Member]
Summary of Significant Accounting Policies [Line Items]
Distribution Made to Limited Liability Company (LLC) Member, Distributions Paid, Per Unit			$ 0.309	$ 0.298
Buckthorn Solar Drop Down Asset [Member]
Summary of Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Noncontrolling Interest										(21)
Capital contributions from tax equity investors, net of distributions		$ 80
Customer Contracts [Member]
Summary of Significant Accounting Policies [Line Items]
Accounts Receivable, Net			$ 29				29
Lease Agreements [Member]
Summary of Significant Accounting Policies [Line Items]
Accounts Receivable, Net			103				103
Conventional Generation [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax			0				0
Capitalized Contract Cost, Amortization			2				3
Total operating revenues			85		83		164	158
Operating Leases, Income Statement, Contingent Revenue			(87)				(167)
Renewables [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax			14				26
Capitalized Contract Cost, Amortization			16				31
Total operating revenues			177		165		275	267
Operating Leases, Income Statement, Contingent Revenue			(179)				(280)
Thermal [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax			44				93
Capitalized Contract Cost, Amortization			0				1
Total operating revenues			45		40		93	84
Operating Leases, Income Statement, Contingent Revenue			(1)				(1)
Energy Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		238				398
Operating Leases, Income Statement, Contingent Revenue			(182)				(284)
Energy Revenue [Member] | Conventional Generation [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		2				3
Operating Leases, Income Statement, Contingent Revenue			(2)				(3)
Energy Revenue [Member] | Renewables [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		193				306
Operating Leases, Income Statement, Contingent Revenue			(179)				(280)
Energy Revenue [Member] | Thermal [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		43				89
Operating Leases, Income Statement, Contingent Revenue			(1)				(1)
Capacity Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		87				169
Operating Leases, Income Statement, Contingent Revenue			(85)				(164)
Capacity Revenue [Member] | Conventional Generation [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		85				164
Operating Leases, Income Statement, Contingent Revenue			(85)				(164)
Capacity Revenue [Member] | Renewables [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		0				0
Operating Leases, Income Statement, Contingent Revenue			0				0
Capacity Revenue [Member] | Thermal [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]		2				5
Operating Leases, Income Statement, Contingent Revenue			$ 0				$ 0
Previously Reported [Member]
Summary of Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Noncontrolling Interest	[1]									$ (391)
Pre-acquisition net income of the Buckthorn Solar Drop Down Asset	[3]				0			12
Total operating revenues	[3]				$ 284			$ 502
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840:
[3]	As previously reported in the Company's Form 10-Q for the quarter ended June 30, 2017

Business Acquisitions Busines36

Business Acquisitions Business Acquisitions - UPMC Thermal (Details) $ in Millions		Mar. 31, 2018USD ($)	Jun. 30, 2018MW	Jun. 19, 2018USD ($)
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts	[1],[2]		5,251
UPMC Thermal [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred | $		$ 84
Accounts Payable, Related Parties | $				$ 4
Thermal [Member]
Business Acquisition [Line Items]
Steam and Chilled Water Capacity, Megawatts Thermal Equivalent	[1],[3]		1,392
Power Generation Capacity, Megawatts	[1]		133
UPMC Thermal [Member] | Thermal [Member]
Business Acquisition [Line Items]
Steam and Chilled Water Capacity, Megawatts Thermal Equivalent			73
Power Generation Capacity, Megawatts			7.5
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.
[3]	For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers.

Business Acquisitions Busines37

Business Acquisitions Business Acquisitions - Central CA Fuel Cell (Details) $ in Millions		Apr. 18, 2018USD ($)MW	Jun. 30, 2018MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts	[1],[2]		5,251
Central CA Fuel Cell 1 [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred | $		$ 11
Power Generation Capacity, Megawatts		2.8
Power Purchase Agreement Period		20 years
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.

Business Acquisitions Busines38

Business Acquisitions Business Acquisitions - Buckthorn Solar Drop Down Asset (Details) $ in Millions		Mar. 31, 2018USD ($)	Jun. 30, 2018USD ($)MW	Mar. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW	[1],[2]		5,251
Long-term Debt			$ 5,970		$ 6,083
Buckthorn Solar Drop Down Asset [Member]
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW			154
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets			$ 20
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			212
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets			3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			235
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	[3]		176
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other			15
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			191
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value				$ 19
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			$ 25
Business Combination, Consideration Transferred		$ 42
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.
[3]	Net of $7 million of net debt issuance costs.

Business Acquisitions Busines39

Business Acquisitions Business Acquisitions - November 2017 Drop Down (Details) $ in Millions		Nov. 02, 2017USD ($)	Jun. 30, 2018USD ($)MW	Dec. 31, 2017USD ($)	Nov. 01, 2017USD ($)MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW	[1],[2]		5,251
Long-term Debt			$ 5,970	$ 6,083
November 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW					38
Business Combination, Consideration Transferred		$ 74
November 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Long-term Debt					$ 26
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.

Business Acquisitions Busines40

Business Acquisitions Business Acquisitions - August 2017 Drop Down (Details) - USD ($) $ in Millions		Mar. 31, 2018	Nov. 02, 2017	Aug. 02, 2017	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017		Aug. 01, 2017
Business Acquisition [Line Items]
Total operating revenues					$ 307	$ 288	[1]	$ 532	$ 509	[1]
Operating Income (Loss)					144	125	[1]	193	179	[1]
Net Income (Loss)					96	44	[1]	96	42	[1]
Less: Pre-acquisition net income of Drop Down Assets					0	2	[1]	4	15	[1]
Less: Income (loss) attributable to noncontrolling interests					17	14	[1]	(3)	2	[1]
Net Income (Loss) Available to Common Stockholders, Basic					79	28	[1]	95	25	[1]
Buckthorn Solar Drop Down Asset [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 42
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net					25			25
Total operating revenues						0			0
Operating Income (Loss)						0			0
Net Income (Loss)						(3)			(3)
Less: Pre-acquisition net income of Drop Down Assets						(3)			(3)
Less: Income (loss) attributable to noncontrolling interests						0			0
Net Income (Loss) Available to Common Stockholders, Basic						0			0
August 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred				$ 44
Business Combination, Contingent Consideration, Liability					$ 8			$ 8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net											$ 87
Total operating revenues						0			0
Operating Income (Loss)						0			0
Net Income (Loss)						0			0
Less: Pre-acquisition net income of Drop Down Assets						3			5
Less: Income (loss) attributable to noncontrolling interests						(3)			(5)
Net Income (Loss) Available to Common Stockholders, Basic						0			0
November 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			$ 74
Total operating revenues						4			7
Operating Income (Loss)						3			3
Net Income (Loss)						2			1
Less: Pre-acquisition net income of Drop Down Assets						2			1
Less: Income (loss) attributable to noncontrolling interests						0			0
Net Income (Loss) Available to Common Stockholders, Basic						0			0
August 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired											25.00%
Previously Reported [Member]
Business Acquisition [Line Items]
Total operating revenues	[2]					284			502
Operating Income (Loss)	[2]					122			176
Net Income (Loss)	[2]					45			44
Less: Pre-acquisition net income of Drop Down Assets	[2]					0			12
Less: Income (loss) attributable to noncontrolling interests	[2]					17			7
Net Income (Loss) Available to Common Stockholders, Basic	[2]					$ 28			$ 25
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	As previously reported in the Company's Form 10-Q for the quarter ended June 30, 2017

Business Acquisitions Busines41

Business Acquisitions Business Acquisitions - March 2017 Drop Down (Details) $ in Millions		Mar. 27, 2017USD ($)MW	Jun. 30, 2018USD ($)MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW	[1],[2]		5,251
Agua Caliente Borrower 2 [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage			16.00%
Percentage of NRG's Ownership		31.00%
Power Generation Capacity, Megawatts | MW		46
Power Purchase Agreement Period		25 years
Remaining Power Purchase Agreement term		22 years
Non-Recourse Debt		$ 41
Utah Portfolio [Member]
Business Acquisition [Line Items]
Remaining Power Purchase Agreement term		20 years
Percentage of Cash Available for Distributions			50.00%
Non-Recourse Debt		$ 287
March 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		128
Business Acquisition, Consideration Transferred, Working Capital			$ 3
Business Combination, Separately Recognized Transactions, Net Gains and Losses		$ 8
NRG [Member] | Agua Caliente Borrower 2 [Member]
Business Acquisition [Line Items]
Percentage of Ownership		51.00%
NRG [Member] | Utah Portfolio [Member]
Business Acquisition [Line Items]
Percentage of Cash Available for Distributions			50.00%
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.

Variable Interest Entities Vari

Variable Interest Entities Variable Interest Entities - Consolidated Entities (Details) $ in Millions		May 31, 2018USD ($)	Mar. 31, 2018USD ($)	Jun. 30, 2018USD ($)MW	Jun. 30, 2017USD ($)		Jun. 30, 2018USD ($)MW	Jun. 30, 2017USD ($)		Mar. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Power Generation Capacity, Megawatts | MW	[1],[2]			5,251			5,251
Long-term Debt				$ 5,970			$ 5,970				$ 6,083
Other Assets				2,600			2,600				2,597	[3]
Property, Plant and Equipment, Net				5,376			5,376				5,410	[3]
Total Assets				8,448			8,448				8,489	[3]
Liabilities				6,161			6,161				6,330	[3]
Less: Income (loss) attributable to noncontrolling interests				17	$ 14	[3]	(3)	$ 2	[3]
November 2015 Drop Down Assets [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets				163			163
Property, Plant and Equipment, Net				362			362
Intangible Assets				2			2
Total Assets				527			527
Liabilities				184			184
Noncontrolling Interest in Variable Interest Entity				10			10
Net Assets				333			333
Alta X and XI TE Holdco [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets				23			23
Property, Plant and Equipment, Net				423			423
Intangible Assets				256			256
Total Assets				702			702
Liabilities				9			9
Noncontrolling Interest in Variable Interest Entity				72			72
Net Assets				621			621
Spring Canyon [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets				1			1
Property, Plant and Equipment, Net				93			93
Intangible Assets				0			0
Total Assets				94			94
Liabilities				4			4
Noncontrolling Interest in Variable Interest Entity				48			48
Net Assets				42			42
Buckthorn Solar Drop Down Asset [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets				24			24
Property, Plant and Equipment, Net				226			226
Intangible Assets				0			0
Total Assets				250			250
Liabilities				141			141
Noncontrolling Interest in Variable Interest Entity				48			48
Net Assets				$ 61			61
Proceeds from Noncontrolling Interests		$ 80
Less: Income (loss) attributable to noncontrolling interests							$ 51
Buckthorn Solar Drop Down Asset [Member]
Schedule of Equity Method Investments [Line Items]
Power Generation Capacity, Megawatts | MW				154			154
Business Combination, Consideration Transferred			$ 42
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value										$ 19
Less: Income (loss) attributable to noncontrolling interests					$ 0			$ 0
Buckthorn Solar, due 2025 [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt		$ 132		$ 132			$ 132				$ 169
Buckthorn Solar, due 2025 [Member] | Buckthorn Solar Drop Down Asset [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt										$ 183
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.
[3]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Variable Interest Entities Va43

Variable Interest Entities Variable Interest Entities - Unconsolidated Entities (Details) $ in Millions		6 Months Ended
		Jun. 30, 2018USD ($)MW	Dec. 31, 2017USD ($)	[1]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		$ 1,183	$ 1,178
Power Generation Capacity, Megawatts | MW	[2],[3]	5,251
Four Brothers Solar [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		$ 209
Granite Mountain Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		76
Iron Springs Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		53
Gen Conn Energy LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		100
NRG DGPV Holdco 1 [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		81
Payments to Acquire Interest in Subsidiaries and Affiliates		4
Due to Affiliate		$ 3
Power Generation Capacity, Megawatts | MW		52
Remaining Lease Term		18 years
NRG RPV Holdco [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		$ 46
NRG DGPV Holdco 2 [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		61
NRG DGPV Holdco 3 [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		75
Payments to Acquire Interest in Subsidiaries and Affiliates		12
Due to Affiliate		$ 10
Power Generation Capacity, Megawatts | MW		59
Remaining Lease Term		21 years
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[3]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.

Variable Interest Entities Va44

Variable Interest Entities Variable Interest Entities - Utah Solar Portfolio (Details) - Utah Portfolio [Member]	Jun. 30, 2018
Variable Interest Entity [Line Items]
Percentage of Cash Available for Distributions	50.00%
Capital Unit, Class A [Member]
Variable Interest Entity [Line Items]
Percentage of Ownership	100.00%
Financial Institutions [Member] | Capital Unit, Class B [Member]
Variable Interest Entity [Line Items]
Taxable Income Allocation, Pre-Flip	99.00%
Taxable Income Allocation, Post-Flip	50.00%

Variable Interest Entities Va45

Variable Interest Entities Variable Interest Entities - Debt Held by Unconsolidated Affiliates (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Long-term Debt	$ 5,970	$ 6,083
Agua Caliente [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt	$ 812
Debt Instrument, Basis Spread on Libor Rate	0.375%
Agua Caliente Borrower 2 [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	16.00%
Pro-Rate Share of Debt Held by Unconsolidated Affiliates	$ 130

Fair Value of Financial Instr46

Fair Value of Financial Instruments Fair Value of Financial Instruments - Balance Sheet Grouping (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financing Receivable, Net		$ 6	$ 13
Long-term Debt and Capital Lease Obligations, Including Current Maturities	[1]	5,936	6,099
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financing Receivable, Net		6	13
Long-term Debt and Capital Lease Obligations, Including Current Maturities	[1]	5,957	6,066
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt and Capital Lease Obligations, Including Current Maturities		1,456	1,502
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt and Capital Lease Obligations, Including Current Maturities		$ 4,480	$ 4,597
[1]	(a) Excludes deferred financing costs, which are recorded as a reduction to long-term debt on the Company's consolidated balance sheets.

Fair Value of Financial Instr47

Fair Value of Financial Instruments Fair Value of Financial Instruments - Recurring Fair Value (Details) - USD ($)		Jun. 30, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	$ 24,000,000		$ 2,000,000
Derivative Liability, Fair Value, Gross Liability		18,000,000		49,000,000
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[2]	24,000,000		2,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value, Gross Liability	[2]	18,000,000		49,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net		0		0
Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset				1,000,000
Derivative Liability, Fair Value, Gross Liability		1,000,000	[3]	1,000,000
Commodity Contract [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[2]	0		1,000,000
Derivative Liability, Fair Value, Gross Liability	[2]	1,000,000		1,000,000
Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		24,000,000		1,000,000
Derivative Liability, Fair Value, Gross Liability		17,000,000		48,000,000
Interest Rate Contract [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[2]	24,000,000		1,000,000
Derivative Liability, Fair Value, Gross Liability	[2]	$ 17,000,000		$ 48,000,000
[1]	Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of June 30, 2018 and December 31, 2017.
[2]	(a) There were no derivative assets or liabilities classified as Level 1 or Level 3 as of June 30, 2018 and December 31, 2017.
[3]	There were no commodity contracts classified as derivative assets as of June 30, 2018.

Fair Value of Financial Instr48

Fair Value of Financial Instruments Fair Value of Financial Instruments - Credit Risk and Derivative FV Measurements (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value Assets, Valuation Techniques, Impact of Credit Reserve to Fair Value	$ 0
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 2,600
Estimated Counterparty Credit Risk Exposure to Certain Counterparties, Period	5 years

Accounting for Derivative Ins49

Accounting for Derivative Instruments and Hedging Activities Accounting for Derivative Instruments and Hedging Activities - FV of Derivatives (Details) - USD ($) $ in Millions		Jun. 30, 2018		Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	$ 24		$ 2
Derivative Liability, Fair Value, Gross Liability		18		49
Fair Value of Gross Derivative Assets/(Liabilities), Net		6		(47)
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset		0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral		6		(47)
Derivative, Collateral, Right to Reclaim Cash		0		0
Derivative, Collateral, Obligation to Return Cash		0		0
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	10		1
Derivative Liability, Fair Value, Gross Liability		6		13
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	14		1
Derivative Liability, Fair Value, Gross Liability		12		36
Interest Rate Contract Current [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	1		0
Derivative Liability, Fair Value, Gross Liability		1		4
Interest Rate Contract Current [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	0		0
Derivative Liability, Fair Value, Gross Liability		4		13
Interest Rate Contract Non Current [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	9		1
Derivative Liability, Fair Value, Gross Liability		5		9
Interest Rate Contract Non Current [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	14		0
Derivative Liability, Fair Value, Gross Liability		7		22
Commodity Contract Current [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]			1
Derivative Liability, Fair Value, Gross Liability		1		1
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset				1
Derivative Liability, Fair Value, Gross Liability		1	[2]	1
Derivative Asset, Fair Value, Gross Liability				0
Derivative Liability, Fair Value, Gross Asset		0	[2]	0
Derivative Asset				1
Derivative Liability		1	[2]	1
Fair Value of Gross Derivative Assets/(Liabilities), Net		(1)	[2]	0
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset		0	[2]	0
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral		(1)	[2]	0
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		24		1
Derivative Liability, Fair Value, Gross Liability		17		48
Derivative Asset, Fair Value, Gross Liability		2		1
Derivative Liability, Fair Value, Gross Asset		2		1
Derivative Asset		22		0
Derivative Liability		15		47
Fair Value of Gross Derivative Assets/(Liabilities), Net		7		(47)
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset		0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral		7		(47)
Interest [Member] | United States of America, Dollars
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,972		2,050
Natural Gas [Member] | MMbtu [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		$ 1		$ 2
[1]	Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of June 30, 2018 and December 31, 2017.
[2]	There were no commodity contracts classified as derivative assets as of June 30, 2018.

Accounting for Derivative Ins50

Accounting for Derivative Instruments and Hedging Activities Accounting for Derivative Instruments and Hedging Activities - AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017		Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Derivative [Line Items]
Accumulated Other Comprehensive Loss, Net of Tax	$ (36)	$ (70)	$ (36)	$ (70)	$ (43)	$ (60)		$ (64)	$ (70)
Accumulated Other Comprehensive Loss, Cumulative Change in Loss from Cash Flow Hedges, Tax Amount	(6)		(6)							$ (16)
Reclassified from accumulated OCL to income due to realization of previously deferred amounts	2	2	6	6
Mark-to-market of cash flow hedge accounting contracts	5	(8)	18	(6)
Accumulated other comprehensive loss	(17)	(28)	(17)	(28)		$ (28)	[1]
Losses expected to be realized from OCL during the next 12 months, net of income tax benefit of $1			9
Losses expected to be realized from OCL during the next 12 months, Tax Amount	(1)		(1)
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net				0
Noncontrolling Interest [Member]
Derivative [Line Items]
Accumulated other comprehensive loss	$ (19)	$ (42)	$ (19)	$ (42)
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Accounting for Derivative Ins51

Accounting for Derivative Instruments and Hedging Activities Accounting for Derivative Instruments and Hedging Activities - Impact to Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (7)	$ (13)	$ (31)	$ (9)

Long-term Debt Long-term Debt -

Long-term Debt Long-term Debt - Debt Table (Details) - USD ($) $ in Millions		Apr. 30, 2018	Jun. 30, 2018		May 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt			$ 5,970			$ 6,083
Current portion of long-term debt			(651)	[1]		(339)	[2]
Debt Issuance Costs, Net			(62)			(68)
Long-term Debt, Excluding Current Maturities			5,244			5,659
Debt Instrument, Unamortized Discount	[3]		(13)			(17)
3.5% Convertible Notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 345			345
Debt Instrument, Interest Rate, Stated Percentage	[4]		3.50%
3.25% Convertible Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 288			288
Debt Instrument, Interest Rate, Stated Percentage	[4]		3.25%
5.375% Senior Notes due in 2024 [Member]
Debt Instrument [Line Items]
Senior Notes			$ 500			500
Debt Instrument, Interest Rate, Stated Percentage	[4]		5.375%
5.00% Senior Notes due in 2026 [Member]
Debt Instrument [Line Items]
Senior Notes			$ 350			350
Debt Instrument, Interest Rate, Stated Percentage	[4]		5.00%
NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 0			55
Debt Instrument, Description of Variable Rate Basis	[4],[5]		3 month LIBOR
Debt Instrument, Basis Spread on Variable Rate	[3]	2.50%	1.75%	[5]
Agua Caliente Borrower 2 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 40			41
Debt Instrument, Interest Rate, Stated Percentage	[4]		5.43%
Alpine Financing Agreement, due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 133			135
Debt Instrument, Description of Variable Rate Basis	[4]		3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate			1.75%
Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 901			926
Buckthorn Solar, due 2025 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 132		$ 132	169
Debt Instrument, Description of Variable Rate Basis			1-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate			1.75%
CVSR, due 2037
Debt Instrument [Line Items]
Long-term Debt			$ 731			746
CVSR Holdco due 2037 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 188			194
Debt Instrument, Interest Rate, Stated Percentage	[4]		4.68%
El Segundo Energy Center, due 2023
Debt Instrument [Line Items]
Long-term Debt			$ 369			400
Debt Instrument, Description of Variable Rate Basis	[4]		3-Month LIBOR
West Holdings Credit Agreement due 2023 Tranche B [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate			2.375%
West Holdings Credit Agreement due 2023 Tranche A [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate			1.75%
Energy Center Minneapolis Series C Notes, due 2025
Debt Instrument [Line Items]
Long-term Debt			$ 0			83
Debt Instrument, Interest Rate, Stated Percentage	[4]		5.95%
Energy Center Minneapolis Series D Notes, due 2031
Debt Instrument [Line Items]
Long-term Debt			$ 125			125
Debt Instrument, Interest Rate, Stated Percentage	[4]		3.55%
NRG Energy Center Minneapolis Series E, F, G, H Notes [Member] [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 203			0
Letters of Credit Outstanding, Amount			0
Laredo Ridge Wind, LLC, due in 2026 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 92			95
Debt Instrument, Description of Variable Rate Basis	[4]		3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate			1.875%
Marsh Landing Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 305			318
Debt Instrument, Description of Variable Rate Basis	[4]		3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate			2.125%
Tapestry Wind LLC due in 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 155			162
Debt Instrument, Description of Variable Rate Basis	[4]		3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate			1.625%
Utah Solar Portfolio, due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 273			278
Viento Funding II, Inc., due in 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 154			163
Debt Instrument, Description of Variable Rate Basis	[4]		3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate			3.00%
Walnut Creek Energy, LLC, due in 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 254			267
Debt Instrument, Description of Variable Rate Basis	[4]		3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate			1.625%
Other Debt [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 432			443
Letters of Credit Outstanding, Amount			36
Project [Domain]
Debt Instrument [Line Items]
Long-term Debt			$ 4,487			$ 4,545
Minimum [Member] | Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			5.696%
Minimum [Member] | CVSR, due 2037
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.339%
Maximum [Member] | Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			7.015%
Maximum [Member] | CVSR, due 2037
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.775%
Letter of Credit [Member] | NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			$ 67
Letter of Credit [Member] | Agua Caliente Borrower 2 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			17
Letter of Credit [Member] | Alpine Financing Agreement, due 2022 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			16
Letter of Credit [Member] | Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			102
Letter of Credit [Member] | Buckthorn Solar, due 2025 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			16
Letter of Credit [Member] | CVSR, due 2037
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			0
Letter of Credit [Member] | CVSR Holdco due 2037 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			13
Letter of Credit [Member] | El Segundo Energy Center, due 2023
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			138
Letter of Credit [Member] | Energy Center Minneapolis Series C Notes, due 2025
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			0
Letter of Credit [Member] | Energy Center Minneapolis Series D Notes, due 2031
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			0
Letter of Credit [Member] | Laredo Ridge Wind, LLC, due in 2026 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			10
Letter of Credit [Member] | Marsh Landing Term Loan Facility [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			65
Letter of Credit [Member] | Tapestry Wind LLC due in 2021 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			20
Letter of Credit [Member] | Utah Solar Portfolio, due 2022 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			13
Letter of Credit [Member] | Viento Funding II, Inc., due in 2023 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			26
Letter of Credit [Member] | Walnut Creek Energy, LLC, due in 2023 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			$ 93
[1]	The 2019 Convertible Notes become due in February 2019 and are included in current portion of long-term debt on the Company's consolidated balance sheet as of June 30, 2018.
[2]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[3]	Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes.
[4]	As of June 30, 2018, L+ equals 3 month LIBOR plus x%, except for Viento, due 2023 where L+ equals 6 month LIBOR plus 3.00%
[5]	Applicable rate is determined by the borrower leverage ratio, as defined in the credit agreement.

Long-term Debt Long-term Debt53

Long-term Debt Long-term Debt - Debt Disclosures (Details) - USD ($) $ in Millions		Jun. 19, 2018	Apr. 30, 2018	Jun. 30, 2018		Dec. 31, 2017
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 1,500
Long-term Debt				5,970		$ 6,083
CVSR Holdco due 2037 [Member]
Debt Instrument [Line Items]
Long-term Debt				$ 188		194
Debt Instrument, Interest Rate, Stated Percentage	[1]			4.68%
NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding				$ 0
Debt Instrument, Basis Spread on Variable Rate	[2]		2.50%	1.75%	[3]
Long-term Debt				$ 0		55
Buckthorn Solar Drop Down Asset [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate				1.75%
NRG Energy Center Minneapolis Series E Notes [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt		$ 70
Debt Instrument, Interest Rate, Stated Percentage	[1]			4.80%
NRG Energy Center Minneapolis Series F Notes [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt		10
Debt Instrument, Interest Rate, Stated Percentage	[1]			4.60%
NRG Energy Center Minneapolis Series G Notes [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt		83
Debt Instrument, Interest Rate, Stated Percentage	[1]			5.90%
NRG Energy Center Minneapolis Series H Notes [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt		40
Debt Instrument, Interest Rate, Stated Percentage	[1]			4.83%
Energy Center Minneapolis Series C Notes, due 2025
Debt Instrument [Line Items]
Repayments of Debt		(83)
Long-term Debt				$ 0		83
Debt Instrument, Interest Rate, Stated Percentage	[1]			5.95%
NRG Energy Center Minneapolis Series E, F, G, H Notes [Member] [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Debt		203
Letters of Credit Outstanding, Amount				$ 0
Long-term Debt				203		$ 0
Proceeds from (Repayments of) Debt		$ 120
Thermal [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				40
Letter of Credit [Member] | CVSR Holdco due 2037 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount				13
Letter of Credit [Member] | NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount				67
Letter of Credit [Member] | Energy Center Minneapolis Series C Notes, due 2025
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount				$ 0
Buckthorn Solar Drop Down Asset [Member] | Buckthorn Solar Drop Down Asset [Member]
Debt Instrument [Line Items]
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage				80.00%
[1]	As of June 30, 2018, L+ equals 3 month LIBOR plus x%, except for Viento, due 2023 where L+ equals 6 month LIBOR plus 3.00%
[2]	Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes.
[3]	Applicable rate is determined by the borrower leverage ratio, as defined in the credit agreement.

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic		$ 79	$ 28	[1]	$ 95	$ 25	[1]
Common Class A [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic	[2]	$ 27	$ 10		$ 33	$ 9
Weighted Average Number of Shares Outstanding, Basic	[2]	35	35		35	35
Earnings Per Share, Basic	[2]	$ 0.77	$ 0.29		$ 0.94	$ 0.26
Net Income (Loss) Available to Common Stockholders, Diluted	[2]	$ 30	$ 13		$ 40	$ 9
Weighted Average Number of Shares Outstanding, Diluted	[2]	49	49		49	35
Earnings Per Share, Diluted	[2]	$ 0.61	$ 0.26		$ 0.80	$ 0.26
Common Class C [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic	[2]	$ 52	$ 18		$ 62	$ 16
Weighted Average Number of Shares Outstanding, Basic	[2]	67	63		66	63
Earnings Per Share, Basic	[2]	$ 0.77	$ 0.29		$ 0.94	$ 0.26
Net Income (Loss) Available to Common Stockholders, Diluted	[2]	$ 55	$ 21		$ 68	$ 16
Weighted Average Number of Shares Outstanding, Diluted	[2]	78	74		77	63
Earnings Per Share, Diluted	[2]	$ 0.70	$ 0.28		$ 0.89	$ 0.26
3.5% Convertible Notes due 2019 [Member] | Common Class A [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	0		0	15
3.25% Convertible Notes due 2020 [Member] | Common Class C [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	0		0	10
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	(a) Basic and diluted earnings per share might not recalculate due to presenting values in millions rather than whole dollars.

Changes in Capital Structure Ch

Changes in Capital Structure Changes in Capital Structure - Stock Issuance (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 03, 2018	Jun. 30, 2018
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share		$ 0.01
ATM Program, Maximum Dollar Value of Shares to Be Issued		$ 150,000
Common Stock, Shares, Issued		4,392,583
Proceeds from Issuance of Common Stock, Before Commission Fees		$ 77,000
Commission Fees		$ 762
NRG Yield, Inc. [Member]
Class of Stock [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		54.80%
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Voting Interest		45.00%
Subsequent Event [Member]
Class of Stock [Line Items]
Proceeds from Issuance of Common Stock, Before Commission Fees	$ 1,000
ATM program, dollar value of shares remaining	$ 38,000

Changes in Capital Structure 56

Changes in Capital Structure Changes in Capital Structure - Dividends (Details) - $ / shares	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Class of Stock [Line Items]
Dividends Per Common Share, Cash Paid	$ 0.309	$ 0.298
Dividends Payable, Date Declared				Jul. 24, 2018
Common Stock, Dividends, Per Share, Declared				$ 0.320
Dividends Payable, Date to be Paid				Sep. 18, 2018
Dividends Payable, Date of Record				Sep. 4, 2018
Preferred Stock, Shares Authorized	10,000,000			10,000,000		10,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01			$ 0.01
Common Class A [Member]
Class of Stock [Line Items]
Dividends Per Common Share, Cash Paid	0.309		$ 0.27	0.607	$ 0.53
Common Class C [Member]
Class of Stock [Line Items]
Dividends Per Common Share, Cash Paid	$ 0.309		$ 0.27	$ 0.607	$ 0.53

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017		Dec. 31, 2017	[1]
Segment Reporting
Operating revenues	$ 307	$ 288	[1]	$ 532	$ 509	[1]
Cost of operations	74	77		163	162
Depreciation and amortization	82	79	[1]	163	156	[1]
General and administrative	6	6	[1]	11	10	[1]
Acquisition-related transaction and integration costs	1	1	[1]	2	2	[1]
Operating Income (Loss)	144	125	[1]	193	179	[1]
Equity in earnings of unconsolidated affiliates	29	16	[1]	33	35	[1]
Other income, net	1	1	[1]	2	2	[1]
Loss on debt extinguishment	0	0	[1]	0	(2)	[1]
Interest expense	(71)	(90)	[1]	(126)	(165)	[1]
Income (loss) before income taxes	103	52	[1]	102	49	[1]
Income tax expense	7	8	[1]	6	7	[1]
Net Income (Loss)	96	44	[1]	96	42	[1]
Total Assets	8,448			8,448			$ 8,489
Conventional Generation
Segment Reporting
Operating revenues	85	83		164	158
Cost of operations	10	15		32	37
Depreciation and amortization	24	26		50	50
General and administrative	0	0		0	0
Acquisition-related transaction and integration costs	0	0		0	0
Operating Income (Loss)	51	42		82	71
Equity in earnings of unconsolidated affiliates	2	3		5	6
Other income, net	1	0		1	0
Loss on debt extinguishment					0
Interest expense	(13)	(14)		(20)	(26)
Income (loss) before income taxes	41	31		68	51
Income tax expense	0	0		0	0
Net Income (Loss)	41	31		68	51
Total Assets	1,828			1,828
Renewables [Member]
Segment Reporting
Operating revenues	177	165		275	267
Cost of operations	33	35		67	68
Depreciation and amortization	52	48		102	96
General and administrative	0	0		0	0
Acquisition-related transaction and integration costs	0	0		0	0
Operating Income (Loss)	92	82		106	103
Equity in earnings of unconsolidated affiliates	27	13		28	29
Other income, net	0	0		1	1
Loss on debt extinguishment					(2)
Interest expense	(35)	(53)		(59)	(92)
Income (loss) before income taxes	84	42		76	39
Income tax expense	0	0		0	0
Net Income (Loss)	84	42		76	39
Total Assets	5,937			5,937
Thermal [Member]
Segment Reporting
Operating revenues	45	40		93	84
Cost of operations	31	27		64	57
Depreciation and amortization	6	5		11	10
General and administrative	0	0		0	0
Acquisition-related transaction and integration costs	0	0		0	0
Operating Income (Loss)	8	8		18	17
Equity in earnings of unconsolidated affiliates	0	0		0	0
Other income, net	0	0		0	0
Loss on debt extinguishment					0
Interest expense	(2)	(2)		(4)	(5)
Income (loss) before income taxes	6	6		14	12
Income tax expense	0	0		0	0
Net Income (Loss)	6	6		14	12
Total Assets	512			512
Corporate
Segment Reporting
Operating revenues	0	0		0	0
Cost of operations	0	0		0	0
Depreciation and amortization	0	0		0	0
General and administrative	6	6		11	10
Acquisition-related transaction and integration costs	1	1		2	2
Operating Income (Loss)	(7)	(7)		(13)	(12)
Equity in earnings of unconsolidated affiliates	0	0		0	0
Other income, net	0	1		0	1
Loss on debt extinguishment					0
Interest expense	(21)	(21)		(43)	(42)
Income (loss) before income taxes	(28)	(27)		(56)	(53)
Income tax expense	7	8		6	7
Net Income (Loss)	(35)	$ (35)		(62)	$ (60)
Total Assets	$ 171			$ 171
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Income Taxes (Provision) (Detai

Income Taxes (Provision) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income before income taxes	$ 103	$ 52	[1]	$ 102	$ 49	[1]
Income tax expense	$ 7	$ 8	[1]	$ 6	$ 7	[1]
Effective income tax rate	6.80%	15.40%		5.90%	14.30%
U.S. federal statutory rate (as a percent)				21.00%	35.00%
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Related Party Transactions (Det

Related Party Transactions (Details)		Mar. 31, 2018USD ($)	Jun. 30, 2018USD ($)MW	Jun. 30, 2017USD ($)		Jun. 30, 2018USD ($)MW	Jun. 30, 2017USD ($)		Jun. 19, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Related Party Transaction
General and administrative			$ 6,000,000	$ 6,000,000	[1]	$ 11,000,000	$ 10,000,000	[1]
Power Generation Capacity, Megawatts | MW	[2],[3]		5,251			5,251
NRG [Member]
Related Party Transaction
Revenue from Related Parties			$ 3,000,000	3,000,000		$ 6,000,000	7,000,000
NRG RENOM [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party			8,000,000	6,000,000		15,000,000	12,000,000
Due to Affiliate			4,000,000			4,000,000					$ 5,000,000
Thermal [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party			2,000,000	2		6,000,000	6,000,000
Marsh Landing [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party			6,000,000	3,000,000		9,000,000	6,000,000
Due to Affiliate			1,000,000			1,000,000				$ 1,000,000
NRG Yield [Member] | NRG [Member]
Related Party Transaction
General and administrative			3,000,000	4,000,000		5,000,000	6,000,000
Operations and Maintenance services [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party			10,000,000	9,000,000		20,000,000	19,000,000
Due to Affiliate			9,000,000			9,000,000				$ 13,000,000
Operations and Maintenance services [Member] | GCE Holding LLC [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party			$ 2,000,000	$ 2		3,000,000	$ 3,000,000
Management Service, Base [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party						$ 9,000,000
Thermal [Member]
Related Party Transaction
Steam and Chilled Water Capacity, Megawatts Thermal Equivalent | MW	[2],[4]		1,392			1,392
Power Generation Capacity, Megawatts | MW	[2]		133			133
Thermal [Member] | Thermal [Member]
Related Party Transaction
Power Generation Capacity, Megawatts | MW	[2]		30			30
Thermal [Member] | UPMC Thermal [Member]
Related Party Transaction
Steam and Chilled Water Capacity, Megawatts Thermal Equivalent | MW			73			73
Power Generation Capacity, Megawatts | MW			7.5			7.5
UPMC Thermal [Member]
Related Party Transaction
Business Combination, Consideration Transferred		$ 84,000,000
Accounts Payable, Related Parties									$ 4,000,000
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of June 30, 2018.
[3]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,257 MWs.
[4]	For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers.