NRG Energy (NRG) 10-Q 3 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2018shares
Document And Entity Information [Abstract]
Entity Registrant Name	NRG ENERGY, INC.
Entity Central Index Key	1,013,871
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	314,886,197
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Revenues
Total operating revenues	$ 2,421	$ 2,382
Operating Costs and Expenses
Cost of operations	1,558	1,862
Depreciation and amortization	235	257
Selling, general and administrative	191	260
Reorganization costs	20	0
Development costs	13	17
Total operating costs and expenses	2,017	2,396
Other income - affiliate	0	48
Gain on sale of assets	2	2
Operating Income/(Loss)	406	36
Other Income/(Expense)
Equity in (losses)/earnings of unconsolidated affiliates	(2)	5
Other (expense)/income, net	(3)	13
Loss on debt extinguishment, net	(2)	(2)
Interest expense	(167)	(225)
Total other expense	(174)	(209)
Income/(Loss) from Continuing Operations Before Income Taxes	232	(173)
Income tax benefit	(1)	(4)
Income/(Loss) from Continuing Operations	233	(169)
Loss from discontinued operations, net of income tax	0	(34)
Net Income/(Loss)	233	(203)
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	(46)	(40)
Net Income Attributable to NRG Energy, Inc.	$ 279	$ (163)
Earnings/(Loss) per Share Attributable to NRG Energy, Inc. Common Stockholders
Weighted average number of common shares outstanding — basic (in shares)	318	316
Income/(loss) from continuing operations per weighted average common share — basic (in usd per share)	$ 0.88	$ (0.41)
Loss from discontinued operations per weighted average common share — basic (in usd per share)	0	(0.11)
Earnings/(Loss) per Weighted Average Common Share — Basic (in usd per share)	$ 0.88	$ (0.52)
Weighted average number of common shares outstanding — diluted (in shares)	322	316
Income/(loss) from continuing operations per weighted average common share — diluted (in usd per share)	$ 0.87	$ (0.41)
Loss from discontinued operations per weighted average common share — diluted (in usd per share)	0	(0.11)
Earnings/(Loss) per Weighted Average Common Share — Diluted (in usd per share)	0.87	(0.52)
Dividends Per Common Share (in usd per share)	$ 0.03	$ 0.03

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Comprehensive Income/(Loss) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income/(loss)	$ 233	$ (203)
Other comprehensive income/(loss), net of tax
Unrealized gain on derivatives, net of income tax expense of $0 and $1	14	4
Foreign currency translation adjustments, net of income tax expense of $0 and $0	(2)	7
Defined benefit plans, net of income tax expense of $0 and $0	(1)	0
Other comprehensive income	11	11
Comprehensive Income/(Loss)	244	(192)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	(38)	(39)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	282	(153)
Comprehensive income/(loss) Available for Common Stockholders	$ 282	$ (153)

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gain on derivatives, income tax expense	$ 0	$ 1
Foreign currency translation adjustments, income tax expense	0	0
Defined benefit plans, income tax expense	$ 0	$ 0

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 764	$ 991
Funds deposited by counterparties	241	37
Restricted cash	407	508
Accounts receivable, net	903	1,079
Inventory	528	532
Derivative instruments	1,015	626
Cash collateral paid in support of energy risk management activities	211	171
Accounts receivable - affiliate	73	95
Current assets - held for sale	89	115
Prepayments and other current assets	326	261
Total current assets	4,557	4,415
Property, plant and equipment, net	13,911	13,908
Other Assets
Equity investments in affiliates	1,011	1,038
Goodwill	539	539
Intangible assets, net	1,726	1,746
Nuclear decommissioning trust fund	680	692
Derivative instruments	354	172
Deferred income taxes	136	134
Non-current assets held-for-sale	157	43
Other non-current assets	681	631
Total other assets	5,284	4,995
Total Assets	23,752	23,318
Current Liabilities
Current portion of long-term debt and capital leases	956	688
Accounts payable	787	881
Accounts payable - affiliate	32	33
Derivative instruments	790	555
Cash collateral received in support of energy risk management activities	240	37
Current liabilities held-for-sale	80	72
Accrued expenses and other current liabilities	662	890
Accrued expenses and other current liabilities - affiliate	161	161
Total current liabilities	3,708	3,317
Other Liabilities
Long-term debt and capital leases	15,406	15,716
Nuclear decommissioning reserve	272	269
Nuclear decommissioning trust liability	400	415
Deferred income taxes	20	21
Derivative instruments	264	197
Out-of-market contracts, net	201	207
Non-current liabilities held-for-sale	7	8
Other non-current liabilities	1,136	1,122
Total non-current liabilities	17,706	17,955
Total Liabilities	21,414	21,272
Redeemable noncontrolling interest in subsidiaries	80	78
Commitments and Contingencies
Stockholders’ Equity
Common stock	4	4
Additional paid-in capital	8,379	8,376
Accumulated deficit	(5,982)	(6,268)
Less treasury stock, at cost — 104,518,931 and 101,580,045 shares, at March 31, 2018 and December 31, 2017, respectively	(2,474)	(2,386)
Accumulated other comprehensive loss	(61)	(72)
Noncontrolling interest	2,392	2,314
Total Stockholders’ Equity	2,258	1,968
Total Liabilities and Stockholders’ Equity	$ 23,752	$ 23,318

Condensed Consolidated Balance6

Condensed Consolidated Balance Sheets (Parenthetical) - shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Treasury stock, shares (in shares)	104,518,931	101,580,045

Condensed Consolidated Stateme7

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows from Operating Activities
Net Income/(Loss)	$ 233	$ (203)
Loss from discontinued operations, net of income tax	0	(34)
Income/(loss) from continuing operations	233	(169)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions and equity in earnings of unconsolidated affiliates	12	8
Depreciation and amortization	235	257
Provision for bad debts	15	9
Amortization of nuclear fuel	13	12
Amortization of financing costs and debt discount/premiums	14	15
Adjustment for debt extinguishment	2	0
Amortization of intangibles and out-of-market contracts	22	30
Amortization of unearned equity compensation	13	8
Changes in deferred income taxes and liability for uncertain tax benefits	(3)	1
Changes in nuclear decommissioning trust liability	34	36
Changes in derivative instruments	(247)	38
Changes in collateral deposits in support of energy risk management activities	163	(127)
Gain on sale of emission allowances	(8)	0
Gain on sale of assets	(2)	(2)
Changes in other working capital	(139)	(198)
Cash provided/(used) by continuing operations	357	(82)
Cash provided by discontinued operations	0	15
Net Cash Provided/(Used) by Operating Activities	357	(67)
Cash Flows from Investing Activities
Acquisitions of businesses, net of cash acquired	(62)	(3)
Capital expenditures	(358)	(236)
Decrease in notes receivable	3	4
Purchases of emission allowances	(17)	(9)
Proceeds from sale of emission allowances	23	11
Investments in nuclear decommissioning trust fund securities	(216)	(153)
Proceeds from the sale of nuclear decommissioning trust fund securities	182	117
Proceeds from sale of assets, net of cash disposed of	11	14
Changes in investments in unconsolidated affiliates	2	(12)
Other	0	18
Cash (used)/provided by continuing operations	(432)	(249)
Cash used by discontinued operations	0	(32)
Net Cash (Used)/Provided by Investing Activities	(432)	(281)
Cash Flows from Financing Activities
Payment of dividends to common and preferred stockholders	(10)	(9)
Payment for treasury stock	(93)	0
Net receipts from settlement of acquired derivatives that include financing elements	0	1
Proceeds from issuance of long-term debt	179	193
Payments for short and long-term debt	(228)	(177)
Net contributions from/(distributions to) noncontrolling interests in subsidiaries	110	(5)
Payment of debt issuance costs	(7)	(14)
Other - contingent consideration	0	(10)
Cash used by continuing operations	(49)	(21)
Cash used by discontinued operations	0	(132)
Net Cash Used by Financing Activities	(49)	(153)
Effect of exchange rate changes on cash and cash equivalents	0	(7)
Change in Cash from discontinued operations	0	(149)
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash	(124)	(359)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period	1,536	1,386
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	$ 1,412	$ 1,027

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation General NRG Energy, Inc., or NRG or the Company, is a customer-driven integrated power company built on a portfolio of leading retail electricity brands and diverse generation assets. NRG is continuously focused on serving the energy needs of end-use residential, commercial and industrial customers in competitive markets through multiple brands and channels. The Company: • directly sells energy and innovative, sustainable products and services to retail customers under the names “NRG”, “Reliant” and other retail brand names owned by NRG; • owns and operates approximately 30,000 MW of generation; • engages in the trading of wholesale energy, capacity and related products; and • transacts in and trades fuel and transportation services. The accompanying unaudited interim condensed 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 generally accepted accounting principles 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 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 condensed 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 March 31, 2018 , and the results of operations, comprehensive income/(loss) and cash flows for the three months ended March 31, 2018 and 2017 . GenOn Chapter 11 Cases On June 14, 2017, GenOn, along with GenOn Americas Generation and certain of their directly and indirectly-owned subsidiaries, or collectively the GenOn Entities, filed voluntary petitions for relief under Chapter 11, or the Chapter 11 Cases, of the U.S. Bankruptcy Code, in the U.S. Bankruptcy Court for the Southern District of Texas, Houston Division, or the Bankruptcy Court. GenOn Mid-Atlantic, as well as its consolidated subsidiaries, REMA and certain other subsidiaries, did not file for relief under Chapter 11. As a result of the bankruptcy filings and beginning on June 14, 2017, GenOn and its subsidiaries were deconsolidated from NRG’s consolidated financial statements. NRG determined that this disposal of GenOn and its subsidiaries is a discontinued operation and, accordingly, the financial information for all historical periods has been recast to reflect GenOn as a discontinued operation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates. Reclassifications Certain prior year amounts have been reclassified for comparative purposes. The reclassifications did not affect results from operations, net assets or cash flows.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Other Balance Sheet Information The following table presents the allowance for doubtful accounts included in accounts receivable, net; accumulated depreciation included in property, plant and equipment, net; accumulated amortization included in intangible assets, net and accumulated amortization included in out-of-market contracts, net: March 31, 2018 December 31, 2017 (In millions) Accounts receivable allowance for doubtful accounts $ 27 $ 28 Property, plant and equipment accumulated depreciation 4,679 4,465 Intangible assets accumulated amortization 1,393 1,818 Out-of-market contracts accumulated amortization 364 358 Restricted Cash The following table provides a reconciliation of cash and cash equivalents, restricted cash and funds deposited by counterparties reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the statement of cash flows. March 31, 2018 December 31, 2017 March 31, 2017 December 31, 2016 (In millions) Cash and cash equivalents $ 764 $ 991 $ 627 $ 938 Funds deposited by counterparties 241 37 3 2 Restricted cash 407 508 397 446 Cash and cash equivalents, funds deposited by counterparties and restricted cash shown in the statement of cash flows $ 1,412 $ 1,536 $ 1,027 $ 1,386 Funds deposited by counterparties consist of cash held by the Company as a result of collateral posting obligations from its counterparties. Some amounts are segregated into separate accounts that are not contractually restricted but, based on the Company's intention, are not available for the payment of general corporate obligations. Depending on market fluctuations and the settlement of the underlying contracts, the Company will refund this collateral to the hedge counterparties pursuant to the terms and conditions of the underlying trades. Since collateral requirements fluctuate daily and the Company cannot predict if any collateral will be held for more than twelve months, the funds deposited by counterparties are classified as a current asset on the Company's balance sheet, with an offsetting liability for this cash collateral received within current liabilities. Restricted cash consists primarily of funds held to satisfy the requirements of certain debt agreements and funds held within the Company's projects that are restricted in their use. Noncontrolling Interest The following table reflects the changes in NRG's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 2,314 Dividends paid to NRG Yield, Inc. public shareholders (30 ) Distributions to noncontrolling interest (19 ) Comprehensive loss attributable to noncontrolling interest (22 ) Non-cash adjustments to noncontrolling interest 6 Contributions from noncontrolling interest 147 Sale of assets to NRG Yield, Inc. (4 ) Balance as of March 31, 2018 $ 2,392 Redeemable Noncontrolling Interest The following table reflects the changes in the Company's redeemable noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 78 Distributions to redeemable noncontrolling interest (1 ) Contributions from redeemable noncontrolling interest 12 Non-cash adjustments to redeemable noncontrolling interest 7 Comprehensive loss attributable to redeemable noncontrolling interest (16 ) Balance as of March 31, 2018 $ 80 Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606 using the modified retrospective method applied to contracts which were not completed as of the adoption date. The Company recognized the cumulative effect of initially applying the new standard as a credit to the opening balance of accumulated deficit, resulting in a decrease of approximately $16 million . The adjustment primarily related to costs incurred to obtain a contract with customers and customer incentives. 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. Retail Revenues Gross revenues for energy sales and services to retail customers are recognized as the Company transfers the promised goods and services to the customer. For the majority of its electricity contracts, the Company’s performance obligation with the customer is satisfied over time and performance obligations for its electricity products are recognized as the customer takes possession of the product. The Company also allocates the contract consideration to distinct performance obligation in a contract for which the timing of the revenue recognized is different. Additionally, customer discounts and incentives reduce the contract consideration and are recognized over the term of the contract. Energy sales and services that have been delivered but not billed by period end are estimated. Accrued unbilled revenues are based on estimates of customer usage since the date of the last meter reading provided by the independent system operators or electric distribution companies. Volume estimates are based on daily forecasted volumes and estimated customer usage by class. Unbilled revenues are calculated by multiplying these volume estimates by the applicable rate by customer class. Estimated amounts are adjusted when actual usage is known and billed. As contracts for retail electricity can be for multi-year periods, 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 amount of any unsatisfied performance obligations will vary based on customer usage, which will depend on factors such as weather and customer activity and therefore it is not practicable to estimate such amounts. Energy Revenue Both physical and financial transactions are entered into to optimize the financial performance of the Company's generating facilities. Electric energy revenue is recognized upon transmission to the customer over time, using the output method for measuring progress of satisfaction of performance obligations. Physical transactions, or the sale of generated electricity to meet supply and demand, are recorded on a gross basis in the Company's consolidated statements of operations. The Company applies the invoicing practical expedient, where applicable, in recognizing energy revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Financial transactions, or the buying and selling of energy for trading purposes, are recorded net within operating revenues in the consolidated statements of operations in accordance with ASC 815. Capacity Revenue Capacity revenues consist of revenues billed to a third party at either the market or a negotiated contract price for making installed generation capacity available in order to satisfy system integrity and reliability requirements. Capacity revenues are recognized over time, using the output method for measuring progress of satisfaction of performance obligations. The Company applies the invoicing practical expedient, where applicable, in recognizing capacity revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Capacity revenue contracts mainly consist of: Capacity auctions — The Company's largest sources of capacity revenues are capacity auctions in PJM, ISO-NE, and NYISO. Both ISO-NE and PJM operate a pay-for-performance model where capacity payments are modified based on real-time performance, where NRG's actual revenues will be the combination of revenues based on the cleared auction MWs plus the net of any over- and under-performance of NRG's fleet. In addition, MISO has an annual auction, known as the Planning Resource Auction, or PRA. The Gulf Coast assets situated in the MISO market may participate in this auction. Estimated revenues for cleared auction MWs in the various capacity auctions are $554 million , $508 million , $423 million , $222 million and $57 million for fiscal years 2018 , 2019 , 2020 , 2021 and 2022 , respectively. Resource adequacy and bilateral contracts — In California, there is a resource adequacy requirement that is primarily satisfied through bilateral contracts. Such bilateral contracts are typically short-term resource adequacy contracts. When bilateral contracting does not satisfy the resource adequacy need, such shortfalls can be addressed through procurement tools administered by the CAISO, including the capacity procurement mechanism or reliability must-run contracts. Demand payments from the current long-term contracts are tied to summer peak demand and provide a mechanism for recovering a portion of the costs associated with new or changed environmental laws or regulations. In Texas, capacity and contracted revenues are through bilateral contracts with load serving entities. Long-term PPAs — Energy, capacity and where applicable, renewable attributes, from the majority of 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. Many of these PPAs are accounted for as leases. Renewable Energy Credits As stated above, renewable energy credits 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 inventory 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 table represents the Company’s disaggregation of revenue from contracts with customers for the three months ended March 31, 2018 , along with the reportable segment for each category: Three months ended March 31, 2018 Generation (In millions) Retail Gulf Coast East/West (a) Subtotal Renewables NRG Yield Eliminations Total Energy revenue (a)(b) $ — $ 371 $ 218 $ 589 $ 77 $ 114 $ (161 ) $ 619 Capacity revenue (a)(b) — 67 140 207 — 82 (1 ) 288 Retail revenue Mass customers 1,171 — — — — — (1 ) 1,170 Business solutions customers 316 — — — — — — 316 Total retail revenue 1,487 — — — — — (1 ) 1,486 Mark-to-market for economic hedging activities (c) (6 ) (564 ) (10 ) (574 ) (10 ) — 484 (106 ) Contract amortization — 3 — 3 — (17 ) — (14 ) Other revenue (a)(b) — 86 16 102 19 46 (19 ) 148 Total operating revenue 1,481 (37 ) 364 327 86 225 302 2,421 Less: Lease revenue 6 — 1 1 64 181 — 252 Less: Derivative revenue (6 ) (188 ) 80 (108 ) (10 ) — 484 360 Less: Contract amortization — 3 — 3 — (17 ) — (14 ) Total revenue from contracts with customers $ 1,481 $ 148 $ 283 $ 431 $ 32 $ 61 $ (182 ) $ 1,823 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Retail Gulf Coast East/West Subtotal Renewables NRG Yield Eliminations Total Energy revenue — — — — 61 102 — 163 Capacity revenue — — — — — 79 — 79 Other revenue 6 — 1 1 3 — — 10 (b) The following amounts of energy and capacity revenue relate to derivative instruments and are accounted for under ASC 815. Retail Gulf Coast East/West Subtotal Renewables NRG Yield Eliminations Total Energy revenue — 371 61 432 — — — 432 Capacity revenue — — 26 26 — — — 26 Other revenue — 5 3 8 — — — 8 (c) Revenue relates entirely to unrealized gains and losses on derivative instruments accounted for under ASC 815. Contract Amortization Assets and liabilities recognized from power sales agreements assumed at Fresh Start and 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. Lease Revenue Certain of the Company’s revenues are obtained through PPAs or other contractual agreements. Many of these agreements are accounted for as operating leases under ASC 840 Leases. Certain of these leases have no minimum lease payments and all of the rent is recorded as contingent rent on an actual basis when the electricity is delivered. 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. Contract Balances The following table reflects the contract assets and liabilities included in the Company’s balance sheet as of March 31, 2018 : (In millions) March 31, 2018 Deferred customer acquisition costs $ 85 Accounts receivable, net - Contracts with customers 784 Accounts receivable, net - Leases 81 Accounts receivable, net - Derivative instruments 38 Total accounts receivable, net 903 Unbilled revenues (included within Accounts receivable, net - Contracts with customers) 292 Deferred revenues 63 The Company’s customer acquisition costs consist of broker fees, commission payments and other costs that represent incremental costs of obtaining the contract with customers for which the Company expects to recover. The Company amortizes these amounts over the estimated life of the customer contract. As a practical expedient, the Company expenses the incremental costs of obtaining a contract if the amortization period of the asset would have been one year or less. When the Company receives consideration from the customer that is in excess of the amount due, such consideration is reclassified to deferred revenue, which represents a contract liability. Generally, the Company will recognize revenue from contract liabilities in the next period as the Company satisfies its performance obligations. Recent Accounting Developments - Guidance Adopted in 2018 ASU 2017-07 — In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715) , Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, or ASU No. 2017-07. Current GAAP does not indicate where the amount of net benefit cost should be presented in an entity’s income statement and does not require entities to disclose the amount of net benefit cost that is included in the income statement. The amendments of ASU No. 2017-07 require an entity to report the service cost component of net benefit costs in the same line item as other compensation costs arising from services rendered by the related employees during the applicable service period. The other components of net benefit cost are required to be presented separately from the service cost component and outside the subtotal of income from operations. Further, ASU No. 2017-07 prescribes that only the service cost component of net benefit costs is eligible for capitalization. The Company adopted the amendments of ASU No. 2017-07 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance retrospectively which resulted in an increase in cost of operations of $4 million and a corresponding increase in other income, net on the statement of operations for the three months ended March 31, 2017 . ASU 2016-01 - In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , or ASU No. 2016-01. The amendments of ASU No. 2016-01 eliminate available-for-sale classification of equity investments and require that equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) be generally measured at fair value with changes in fair value recognized in net income. Further, the amendments require that financial assets and financial liabilities be presented separately in the notes to the financial statements, grouped by measurement category and form of financial asset. The guidance in ASU No. 2016-01 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those annual periods. The Company adopted the amendments of ASU No. 2016-01 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance on a modified retrospective basis, which resulted in no material adjustments recorded to the consolidated results of operations, cash flows, and statement of financial position. Recent Accounting Developments - Guidance 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 which includes the evaluation of lease contracts compared to the new standard. 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, NRG believes the adoption of Topic 842 will have a material impact on its financial statements. The Company is also monitoring recent changes to Topic 842 and the related impact on the implementation process.

Discontinued Operations and Dis

Discontinued Operations and Dispositions	3 Months Ended
	Mar. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations and Dispositions	Discontinued Operations and Dispositions This footnote should be read in conjunction with the complete description under Note 3 , Discontinued Operations, Acquisitions and Dispositions , to the Company's 2017 Form 10-K. Discontinued Operations On June 14, 2017, the GenOn Entities filed voluntary petitions for relief under Chapter 11 of the Bankruptcy Code in the Bankruptcy Court. As a result of the bankruptcy filings, NRG has concluded that it no longer controls GenOn as it is subject to the control of the Bankruptcy Court; and, accordingly, NRG no longer consolidates GenOn for financial reporting purposes. By eliminating a large portion of its operations in the PJM market with the deconsolidation of GenOn, NRG has concluded that GenOn meets the criteria for discontinued operations, as this represents a strategic shift in the markets in which NRG operates. As such, all prior period results for GenOn have been reclassified as discontinued operations. Summarized results of discontinued operations were as follows: Three months ended March 31, 2017 (In millions) Operating revenues $ 381 Operating costs and expenses (373 ) Other expenses (44 ) Loss from operations of discontinued components, before tax (36 ) Income tax expense 1 Loss from operations of discontinued components (37 ) Interest income - affiliate 3 Loss from discontinued operations, net of tax $ (34 ) Income recorded from discontinued operations was immaterial for the three months ended March 31, 2018 . Restructuring Support Agreement NRG, GenOn and certain holders representing greater than 93% in aggregate principal amount of GenOn’s Senior Notes and certain holders representing greater than 93% in aggregate principal amount of GenOn Americas Generation’s Senior Notes entered into a Restructuring Support Agreement that provides for a restructuring and recapitalization of the GenOn Entities through a prearranged plan of reorganization that was approved by the Bankruptcy Court pursuant to an order of confirmation. Completion of the agreed upon terms is contingent upon certain milestones in the Restructuring Support Agreement and the satisfaction or waiver or certain conditions precedent. Certain principal terms of the Restructuring Support Agreement and the plan of reorganization are detailed below: 1) The dismissal of litigation and full releases from GenOn and GenOn Americas Generation in favor of NRG upon the earlier of the consummation of the GenOn Entities' plan of reorganization or the Settlement Agreement; a condition precedent to the consummation of the Settlement Agreement is a full release or indemnification in favor of NRG from any claims of GenOn Mid-Atlantic and REMA. 2) NRG will provide settlement cash consideration to GenOn of $261.3 million , which will be paid in cash less any amounts owed to NRG under the intercompany secured revolving credit facility. As of March 31, 2018 , GenOn owed NRG approximately $125 million under the intercompany secured revolving credit facility. See Note 13 , Related Party Transactions , for further discussion of the intercompany secured revolving credit facility. The net liability for these amounts, along with the services credit described below, is recorded in accrued expenses and other current liabilities - affiliate as of March 31, 2018 and December 31, 2017 . 3) NRG will retain the pension liability, including payment of approximately $13 million of 2017 pension contributions, for GenOn employees for service provided prior to the completion of the reorganization, which was paid in September 2017. GenOn’s pension liability as of March 31, 2018 , was approximately $91 million . NRG will also retain the liability for GenOn’s post-employment and retiree health and welfare benefits, in an amount up to $25 million . These liabilities are recorded within other non-current liabilities as of March 31, 2018 and December 31, 2017 . 4) The shared services agreement between NRG and GenOn was terminated and replaced as of the plan confirmation date with a transition services agreement. Under the transition services agreement, NRG will continue to provide the shared services and other separation services at an annualized rate of $84 million , subject to certain credits and adjustments. See Note 13 , Related Party Transactions , for further discussion of the Services Agreement. 5) NRG will provide a credit of $28 million to GenOn to apply against amounts owed under the transition services agreement. Any unused amount can be paid in cash at GenOn’s request. The credit was intended to reimburse GenOn for its payment of financing costs. 6) NRG and GenOn have agreed to cooperate in good faith to maximize the value of certain development projects. Pursuant to this, GenOn made a one-time payment in the amount of $15 million to NRG in December 2017 as compensation for a purchase option with respect to the Canal 3 project. On March 22, 2018, NRG agreed to sell Canal 3 to Stonepeak Kestrel Holdings II LLC in conjunction with GenOn's sale of Canal Units 1 and 2 to Stonepeak Kestrel Holdings LLC. NRG expects to reimburse GenOn for $13.5 million of the one-time payment upon the close of the sale of Canal 3. This amount is recorded as a current liability as of March 31, 2018 , and December 31, 2017 . GenMA Settlement The Bankruptcy Court order confirming the plan of reorganization also approved the settlement terms agreed to among the GenOn Entities, NRG, the Consenting Holders, GenOn Mid-Atlantic, and certain of GenOn Mid-Atlantic’s stakeholders, or the GenMA Settlement, and directed the settlement parties to cooperate in good faith to negotiate definitive documentation consistent with the GenMA Settlement term sheet in order to pursue consummation of the GenMA Settlement. The definitive documentation effectuating the GenMA Settlement was finalized and effective as of April 27, 2018. Certain terms of the compromise with respect to NRG and GenOn Mid-Atlantic are as follows: • Settlement of all pending litigation and objections to the Plan (including with respect to releases and feasibility); • NRG provided $37.5 million in letters of credit as new qualifying credit support to GenOn Mid-Atlantic; and • NRG paid approximately $6 million as reimbursement of professional fees incurred by certain of GenOn Mid-Atlantic's stakeholders in connection with the GenMA Settlement. Transfer of Assets Under Common Control On March 30, 2018, as part of the Transformation Plan, the Company sold to NRG Yield, Inc. 100% of NRG's interests in Buckthorn Renewables, LLC, which owns a 154 -MW construction-stage utility-scale solar generation project, located in Texas. NRG Yield, Inc. paid cash consideration of approximately $42 million , excluding working capital adjustments, and assumed non-recourse debt of approximately $ 183 million . Concurrently, an initial contribution of approximately $19 million was received from the third-party investor in the underlying tax equity partnership, which is included in noncontrolling interest. On March 27, 2017, the Company sold to NRG Yield, Inc.: (i) a 16% interest in the Agua Caliente solar project, representing ownership of approximately 46 net MW of capacity and (ii) NRG's interests in seven utility-scale solar projects located in Utah representing 265 net MW of capacity, which have reached commercial operations. NRG Yield, Inc. paid cash consideration of $130 million , plus $1 million in working capital adjustments, and assumed non-recourse debt of approximately $328 million .

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments This footnote should be read in conjunction with the complete description under Note 4 , Fair Value of Financial Instruments , to the Company's 2017 Form 10-K. For cash and cash equivalents, funds deposited by counterparties, accounts and other receivables, accounts payable, restricted cash, and cash collateral paid and received in support of energy risk management activities, the carrying amount approximates 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 NRG's recorded financial instruments not carried at fair market value are as follows: As of March 31, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable (a) $ 15 $ 14 $ 16 $ 15 Liabilities: Long-term debt, including current portion (b) 16,559 16,687 16,603 16,894 (a) Includes the current portion of notes receivable which is recorded in prepayments and other current assets on the Company's consolidated balance sheets. (b) 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 March 31, 2018 and December 31, 2017 : As of March 31, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 8,772 $ 7,915 $ 8,934 $ 7,960 Recurring Fair Value Measurements Debt securities, equity securities, and trust fund investments, which are comprised of various U.S. debt and equity securities, and derivative assets and liabilities, are carried at fair market value. The following tables present assets and liabilities measured and recorded at fair value on the Company's condensed consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of March 31, 2018 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 22 $ 3 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 16 16 — — U.S. government and federal agency obligations 56 55 1 — Federal agency mortgage-backed securities 92 — 92 — Commercial mortgage-backed securities 16 — 16 — Corporate debt securities 100 — 100 — Equity securities 333 333 — — Foreign government fixed income securities 5 — 5 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 1,277 168 1,060 49 Interest rate contracts 92 — 92 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 62 Total assets $ 2,072 $ 576 $ 1,366 $ 68 Derivative liabilities: Commodity contracts 1,024 224 729 71 Interest rate contracts 30 — 30 — Total liabilities $ 1,054 $ 224 $ 759 $ 71 As of December 31, 2017 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 22 $ 3 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 47 45 2 — U.S. government and federal agency obligations 43 42 1 — Federal agency mortgage-backed securities 82 — 82 — Commercial mortgage-backed securities 14 — 14 — Corporate debt securities 99 — 99 — Equity securities 334 334 — — Foreign government fixed income securities 5 — 5 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 745 191 509 45 Interest rate contracts 53 — 53 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 68 Total assets $ 1,513 $ 616 $ 765 $ 64 Derivative liabilities: Commodity contracts 693 257 359 77 Interest rate contracts 59 — 59 — Total liabilities $ 752 $ 257 $ 418 $ 77 There were no transfers during the three months ended March 31, 2018 and 2017 between Levels 1 and 2. The following tables reconcile, for the three months ended March 31, 2018 and 2017 , the beginning and ending balances for financial instruments that are recognized at fair value in the condensed consolidated financial statements, at least annually, using significant unobservable inputs: Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended March 31, 2018 (In millions) Debt Securities Derivatives (a) Total Beginning balance $ 19 $ (32 ) $ (13 ) Total gains — realized/unrealized: Included in earnings — 2 2 Purchases — 1 1 Transfers into Level 3 (b) — 4 4 Transfers out of Level 3 (b) — 3 3 Ending balance as of March 31, 2018 $ 19 $ (22 ) $ (3 ) Gains for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of March 31, 2018 $ — $ 3 $ 3 (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2. Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended March 31, 2017 (In millions) Debt Securities Trust Fund Investments Derivatives (a) Total Beginning balance $ 17 $ 54 $ (68 ) $ 3 Total gains — realized/unrealized: Included in earnings 1 — 6 7 Included in nuclear decommissioning obligation — 4 — 4 Purchases — — 4 4 Transfers into Level 3 (b) — — (8 ) (8 ) Transfers out of Level 3 (b) — — 10 10 Ending balance as of March 31, 2017 $ 18 $ 58 $ (56 ) $ 20 Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of March 31, 2017 $ — $ — $ (15 ) $ (15 ) (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2. Derivative Fair Value Measurements A portion of NRG's contracts are exchange-traded contracts with readily available quoted market prices. A majority of NRG's contracts are non-exchange-traded contracts valued using prices provided by external sources, primarily price quotations available through brokers or over-the-counter and on-line exchanges. The remainder of the assets and liabilities represent contracts for which external sources or observable market quotes are not available for the whole term or for certain delivery months or the contracts are retail and load following power contracts. These contracts are valued using various valuation techniques including but not limited to internal models that apply fundamental analysis of the market and corroboration with similar markets. As of March 31, 2018 , contracts valued with prices provided by models and other valuation techniques make up 4% of the total derivative assets and 7% of the total derivative liabilities. NRG's significant positions classified as Level 3 include physical and financial power executed in illiquid markets as well as financial transmission rights, or FTRs. The significant unobservable inputs used in developing fair value include illiquid power location pricing which is derived as a basis to liquid locations. The basis spread is based on observable market data when available or derived from historic prices and forward market prices from similar observable markets when not available. For FTRs, NRG uses the most recent auction prices to derive the fair value. The following tables quantify the significant unobservable inputs used in developing the fair value of the Company's Level 3 positions as of March 31, 2018 and December 31, 2017 : Significant Unobservable Inputs March 31, 2018 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 38 $ 63 Discounted Cash Flow Forward Market Price (per MWh) $ 9 $ 319 $ 40 FTRs 11 8 Discounted Cash Flow Auction Prices (per MWh) (28 ) 46 — $ 49 $ 71 Significant Unobservable Inputs December 31, 2017 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 34 $ 65 Discounted Cash Flow Forward Market Price (per MWh) $ 10 $ 142 $ 33 FTRs 11 12 Discounted Cash Flow Auction Prices (per MWh) (28 ) 46 — $ 45 $ 77 The following table provides sensitivity of fair value measurements to increases/(decreases) in significant unobservable inputs as of March 31, 2018 and December 31, 2017 : Significant Unobservable Input Position Change In Input Impact on Fair Value Measurement Forward Market Price Power Buy Increase/(Decrease) Higher/(Lower) Forward Market Price Power Sell Increase/(Decrease) Lower/(Higher) FTR Prices Buy Increase/(Decrease) Higher/(Lower) FTR Prices Sell Increase/(Decrease) Lower/(Higher) The fair value of each contract is discounted using a risk-free interest rate. In addition, the Company applies a credit reserve to reflect credit risk, which is calculated based on published default probabilities. As of March 31, 2018 , the credit reserve resulted in a $2 million decrease in fair value in operating revenue and cost of operations. As of December 31, 2017 , the credit reserve resulted in no change in fair value in operating revenue and cost of operations. Concentration of Credit Risk In addition to the credit risk discussion as disclosed in Note 2 , Summary of Significant Accounting Policies , to the Company's 2017 Form 10-K, the following is a discussion of the concentration of credit risk for the Company's contractual obligations. 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. NRG is exposed to counterparty credit risk through various activities including wholesale sales, fuel purchases and retail supply arrangements, and retail customer credit risk through its retail load activities. Counterparty Credit Risk The Company's counterparty credit risk policies are disclosed in its 2017 Form 10-K. As of March 31, 2018 , the Company's counterparty credit exposure, excluding credit risk exposure under certain long term agreements, was $505 million with net exposure of $244 million . NRG held collateral (cash and letters of credit) against those positions of $264 million . Approximately 83% of the Company's exposure before collateral is expected to roll off by the end of 2019 . Counterparty credit exposure is valued through observable market quotes and discounted at a risk free interest rate. The following tables highlight net counterparty credit exposure by industry sector and by counterparty credit quality. Net counterparty credit exposure is defined as the aggregate net asset position for NRG with counterparties where netting is permitted under the enabling agreement and includes all cash flow, mark-to-market and NPNS, and non-derivative transactions. The exposure is shown net of collateral held, and includes amounts net of receivables or payables. Net Exposure (a) (b) Category by Industry Sector (% of Total) Utilities, energy merchants, marketers and other 78 % Financial institutions 22 Total as of March 31, 2018 100 % Net Exposure (a) (b) Category by Counterparty Credit Quality (% of Total) Investment grade 78 % Non-Investment grade/Non-Rated 22 Total as of March 31, 2018 100 % (a) Counterparty credit exposure excludes uranium and coal transportation contracts because of the unavailability of market prices. (b) The figures in the tables above exclude potential counterparty credit exposure related to RTOs, ISOs, registered commodity exchanges and certain long term contracts. NRG has counterparty credit risk exposure to certain counterparties, each of which represent more than 10% of total net exposure discussed above. The aggregate of such counterparties' exposure was $65 million as of March 31, 2018 . Changes in hedge positions and market prices will affect credit exposure and counterparty concentration. Given the credit quality, diversification and term of the exposure in the portfolio, NRG does not anticipate a material impact on the Company's financial position or results of operations from nonperformance by any of NRG's counterparties. RTOs and ISOs The Company participates in the organized markets of CAISO, ERCOT, ISO-NE, MISO, NYISO and PJM, known as RTOs or ISOs. Trading in these markets is approved by FERC, or in the case of ERCOT, approved by the PUCT and includes credit policies that, under certain circumstances, require that losses arising from the default of one member on spot market transactions be shared by the remaining participants. As a result, the counterparty credit risk to these markets is limited to NRG’s share of overall market and are excluded from the above exposures. Exchange Traded Transactions The Company enters into commodity transactions on registered exchanges, notably ICE and NYMEX. These clearinghouses act as the counterparty and transactions are subject to extensive collateral and margining requirements. As a result, these commodity transactions have limited counterparty credit risk. Long Term Contracts Counterparty credit exposure described above excludes credit risk exposure under certain long term agreements, including California tolling agreements, Gulf Coast load obligations, and wind and solar PPAs. As external sources or observable market quotes are not available to estimate such exposure, the Company estimates its credit exposure for 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 March 31, 2018 , aggregate credit risk exposure managed by NRG to these counterparties was approximately $4.1 billion , including $2.5 billion related to assets of NRG Yield, Inc., for the next five years. This amount excludes potential credit exposures for projects with long-term PPAs that have not reached commercial operations. The majority of these power contracts are with utilities or public power entities 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 or treatment by regulatory agencies which NRG is unable to predict. Retail Customer Credit Risk The Company is exposed to retail credit risk through the Company's retail electricity providers, which serve C&I customers and the Mass market. Retail credit risk results in losses when a customer fails to pay for services rendered. The losses may result from both nonpayment of customer accounts receivable and the loss of in-the-money forward value. The Company manages retail credit risk through the use of established credit policies that include monitoring of the portfolio and the use of credit mitigation measures such as deposits or prepayment arrangements. As of March 31, 2018 , the Company's retail customer credit exposure to C&I and Mass customers was diversified across many customers and various industries, as well as government entities.

Nuclear Decommissioning Trust F

Nuclear Decommissioning Trust Fund	3 Months Ended
	Mar. 31, 2018
Nuclear Decommissioning Trust Fund Disclosure [Abstract]
Nuclear Decommissioning Trust Fund	Nuclear Decommissioning Trust Fund This footnote should be read in conjunction with the complete description under Note 6 , Nuclear Decommissioning Trust Fund , to the Company's 2017 Form 10-K. NRG's Nuclear Decommissioning Trust Fund assets are comprised of securities classified as available-for-sale and recorded at fair value based on actively quoted market prices. NRG accounts for the Nuclear Decommissioning Trust Fund in accordance with ASC 980, Regulated Operations , because the Company's nuclear decommissioning activities are subject to approval by the PUCT with regulated rates that are designed to recover all decommissioning costs and that can be charged to and collected from the ratepayers per PUCT mandate. Since the Company is in compliance with PUCT rules and regulations regarding decommissioning trusts and the cost of decommissioning is the responsibility of the Texas ratepayers, not NRG, all realized and unrealized gains or losses (including other-than-temporary impairments) related to the Nuclear Decommissioning Trust Fund are recorded to the Nuclear Decommissioning Trust liability and are not included in net income or accumulated OCI, consistent with regulatory treatment. The following table summarizes the aggregate fair values and unrealized gains and losses (including other-than-temporary impairments) for the securities held in the trust funds, as well as information about the contractual maturities of those securities. As of March 31, 2018 As of December 31, 2017 (In millions, except otherwise noted) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Cash and cash equivalents $ 16 $ — $ — — $ 47 $ — $ — — U.S. government and federal agency obligations 56 1 1 11 43 1 — 11 Federal agency mortgage-backed securities 92 — 2 23 82 1 1 23 Commercial mortgage-backed securities 16 — 1 22 14 — — 20 Corporate debt securities 100 1 2 11 99 2 1 11 Equity securities 395 265 — — 402 272 — — Foreign government fixed income securities 5 — — 8 5 — — 9 Total $ 680 $ 267 $ 6 $ 692 $ 276 $ 2 The following table summarizes proceeds from sales of available-for-sale securities and the related realized gains and losses from these sales. The cost of securities sold is determined on the specific identification method. Three months ended March 31, 2018 2017 (In millions) Realized gains $ 3 $ 2 Realized losses 3 2 Proceeds from sale of securities 182 117

Accounting for Derivative Instr

Accounting for Derivative Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 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 5 , Accounting for Derivative Instruments and Hedging Activities , to the Company's 2017 Form 10-K. Energy-Related Commodities As of March 31, 2018 , NRG had energy-related derivative instruments extending through 2031 . The Company marks these derivatives to market through the statement of operations. Interest Rate Swaps NRG is exposed to changes in interest rates through the Company's issuance of variable rate debt. In order to manage the Company's interest rate risk, NRG enters into interest rate swap agreements. As of March 31, 2018 , NRG had interest rate derivative instruments on recourse debt extending through 2021 , which are not designated as cash flow hedges. The Company had interest rate swaps 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/(sell) of NRG's open derivative transactions broken out by category, excluding those derivatives that qualified for the NPNS exception, as of March 31, 2018 and December 31, 2017 . Option contracts are reflected using delta volume. Delta volume equals the notional volume of an option adjusted for the probability that the option will be in-the-money at its expiration date. Total Volume March 31, 2018 December 31, 2017 Category Units (In millions) Emissions Short Ton 2 1 Coal Short Ton 17 21 Natural Gas MMBtu (208 ) (17 ) Power MWh 16 14 Capacity MW/Day (1 ) (1 ) Interest Dollars $ 3,938 $ 3,876 Equity Shares 1 1 The increase in the natural gas position was primarily the result of additional generation hedge positions. Fair Value of Derivative Instruments The following table summarizes the fair value within the derivative instrument valuation on the balance sheets: Fair Value Derivative Assets Derivative Liabilities March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 (In millions) Derivatives Designated as Cash Flow or Fair Value Hedges: Interest rate contracts current $ 2 $ 1 $ 2 $ 5 Interest rate contracts long-term 20 11 7 11 Total Derivatives Designated as Cash Flow or Fair Value Hedges 22 12 9 16 Derivatives Not Designated as Cash Flow or Fair Value Hedges: Interest rate contracts current 13 9 7 15 Interest rate contracts long-term 57 32 14 28 Commodity contracts current 1,000 616 781 535 Commodity contracts long-term 277 129 243 158 Total Derivatives Not Designated as Cash Flow or Fair Value Hedges 1,347 786 1,045 736 Total Derivatives $ 1,369 $ 798 $ 1,054 $ 752 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. In addition, collateral received or paid on the Company's derivative assets or liabilities are recorded on a separate line item on the balance sheet. The following table summarizes the offsetting of derivatives by counterparty master agreement level and collateral received or paid: Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of March 31, 2018 (In millions) Commodity contracts: Derivative assets $ 1,277 $ (835 ) $ (201 ) $ 241 Derivative liabilities (1,024 ) 835 120 (69 ) Total commodity contracts 253 — (81 ) 172 Interest rate contracts: Derivative assets 92 (4 ) — 88 Derivative liabilities (30 ) 4 — (26 ) Total interest rate contracts 62 — — 62 Total derivative instruments $ 315 $ — $ (81 ) $ 234 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of December 31, 2017 (In millions) Commodity contracts: Derivative assets $ 745 $ (578 ) $ (11 ) $ 156 Derivative liabilities (693 ) 578 73 (42 ) Total commodity contracts 52 — 62 114 Interest rate contracts: Derivative assets 53 (3 ) — 50 Derivative liabilities (59 ) 3 — (56 ) Total interest rate contracts (6 ) — — (6 ) Total derivative instruments $ 46 $ — $ 62 $ 108 Accumulated Other Comprehensive Loss The following table summarizes the effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax: Interest Rate Contracts Three months ended March 31, 2018 2017 (In millions) Accumulated OCI beginning balance $ (54 ) $ (66 ) Reclassified from accumulated OCI to income: Due to realization of previously deferred amounts 4 3 Mark-to-market of cash flow hedge accounting contracts 19 2 Accumulated OCI ending balance, net of $6, and $14 tax $ (31 ) $ (61 ) Losses expected to be realized from OCI during the next 12 months, net of $2 tax $ (9 ) Amounts reclassified from accumulated OCI into income are recorded to interest expense for interest rate contracts. The Company's regression analysis for Marsh Landing, Walnut Creek, and Avra Valley interest rate swaps, while positively correlated, no longer contain match 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 Unrealized gains and losses associated with changes in the fair value of derivative instruments not accounted for as cash flow hedges are reflected in current period consolidated results of operations. The following table summarizes the pre-tax effects of economic hedges that have not been designated as cash flow hedges and trading activity on the Company's statement of operations. The effect of energy commodity contracts is included within operating revenues and cost of operations and the effect of interest rate contracts is included in interest expense. Three months ended March 31, 2018 2017 Unrealized mark-to-market results (In millions) Reversal of previously recognized unrealized losses on settled positions related to economic hedges $ 2 $ 3 Net unrealized gains/(losses) on open positions related to economic hedges 194 (22 ) Total unrealized mark-to-market gains/(losses) for economic hedging activities 196 (19 ) Reversal of previously recognized unrealized gains on settled positions related to trading activity (3 ) (15 ) Net unrealized gains on open positions related to trading activity 11 1 Total unrealized mark-to-market gains/(losses) for trading activity 8 (14 ) Total unrealized gains/(losses) $ 204 $ (33 ) Three months ended March 31, 2018 2017 (In millions) Unrealized (losses)/gains included in operating revenues $ (98 ) $ 104 Unrealized gains/(losses) included in cost of operations 302 (137 ) Total impact to statement of operations — energy commodities $ 204 $ (33 ) Total impact to statement of operations — interest rate contracts $ 48 $ 5 The reversals of acquired gain or loss positions were valued based upon the forward prices on the acquisition date. The roll-off amounts were offset by realized gains or losses at the settled prices and are reflected in operating revenue or cost of operations during the same period. For the three months ended March 31, 2018 , the $194 million unrealized gain from open economic hedge positions was primarily the result of an increase in value of forward purchases of ERCOT heat rate contracts due to ERCOT heat rate expansion. For the three months ended March 31, 2017 , the $22 million unrealized loss from open economic hedge positions was primarily the result of a decrease in value of forward purchases of natural gas, coal, and ERCOT electricity due to decreases in natural gas, coal, and ERCOT electricity prices. Credit Risk Related Contingent Features Certain of the Company's hedging agreements contain provisions that require the Company to post additional collateral if the counterparty determines that there has been deterioration in credit quality, generally termed “adequate assurance” under the agreements, or require the Company to post additional collateral if there were a one notch downgrade in the Company's credit rating. The collateral required for contracts with adequate assurance clauses that are in a net liability position as of March 31, 2018 , was $20 million . The collateral required for contracts with credit rating contingent features that are in a net liability position as of March 31, 2018 , was $5 million . The Company is also a party to certain marginable agreements under which it has a net liability position, but the counterparty has not called for the collateral due, which was approximately $5 million as of March 31, 2018 . See Note 4 , Fair Value of Financial Instruments , to this Form 10-Q for discussion regarding concentration of credit risk.

Debt and Capital Leases

Debt and Capital Leases	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Debt and Capital Leases	Debt and Capital Leases This footnote should be read in conjunction with the complete description under Note 12 , Debt and Capital Leases , to the Company's 2017 Form 10-K. Long-term debt and capital leases consisted of the following: (In millions, except rates) March 31, 2018 December 31, 2017 March 31, 2018 interest rate % (a) Recourse debt: Senior notes, due 2022 992 992 6.250 Senior notes, due 2024 733 733 6.250 Senior notes, due 2026 1,000 1,000 7.250 Senior notes, due 2027 1,250 1,250 6.625 Senior notes, due 2028 870 870 5.750 Term loan facility, due 2023 1,867 1,872 L+1.75 Tax-exempt bonds 465 465 4.125 - 6.00 Subtotal recourse debt 7,177 7,182 Non-recourse debt: NRG Yield, Inc. Convertible Senior Notes, due 2019 345 345 3.500 NRG Yield, Inc. Convertible Senior Notes, due 2020 288 288 3.250 NRG Yield Operating LLC Senior Notes, due 2024 500 500 5.375 NRG Yield Operating LLC Senior Notes, due 2026 350 350 5.000 NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2023 (b) 75 55 L+2.500 El Segundo Energy Center, due 2023 369 400 L+1.75 - L+2.375 Marsh Landing, due 2023 309 318 L+2.125 Alta Wind I - V lease financing arrangements, due 2034 and 2035 926 926 5.696 - 7.015 Walnut Creek, term loans due 2023 259 267 L+1.625 Utah Portfolio, due 2022 278 278 various Tapestry, due 2021 158 162 L+1.625 CVSR, due 2037 731 746 2.339 - 3.775 CVSR HoldCo, due 2037 188 194 4.680 Alpine, due 2022 135 135 L+1.750 Energy Center Minneapolis, due 2025 83 83 5.95 Energy Center Minneapolis, due 2031 125 125 3.55 Viento, due 2023 163 163 L+3.00 Buckthorn Solar, due 2018 and 2025 183 169 L+1.750 NRG Yield - other 573 579 various Subtotal NRG Yield debt (non-recourse to NRG) (c) 6,038 6,083 Ivanpah, due 2033 and 2038 1,068 1,073 2.285 - 4.256 Carlsbad Energy Project (c) 475 427 L+1.625 - 4.120 Agua Caliente, due 2037 815 818 2.395 - 3.633 Agua Caliente Borrower 1, due 2038 86 89 5.430 Cedro Hill, due 2025 (c) 149 151 L+1.75 Midwest Generation, due 2019 132 152 4.390 NRG Other Renewables (c) 466 478 various NRG Other 178 180 various Subtotal other NRG non-recourse debt 3,369 3,368 Subtotal all non-recourse debt 9,407 9,451 Subtotal long-term debt (including current maturities) 16,584 16,633 Capital leases 4 5 various Subtotal long-term debt and capital leases (including current maturities) 16,588 16,638 Less current maturities (d) (956 ) (688 ) Less debt issuance costs (201 ) (204 ) Discounts (25 ) (30 ) Total long-term debt and capital leases $ 15,406 $ 15,716 (a) As of March 31, 2018 , L+ equals 3 month LIBOR plus x%, except for the 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) Debt associated with the asset sales announced in February 2018 (d) The NRG Yield, Inc. Convertible Senior Notes, due 2019, become due in February 2019 and are recorded in current maturities as of March 31, 2018. Recourse Debt 2023 Term Loan Facility On March 21, 2018, NRG repriced the 2023 Term Loan Facility, reducing the interest rate margin by 50 basis points to LIBOR plus 1.75% and reducing the LIBOR floor to 0.00% . Non-recourse Debt NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility NRG Yield LLC and its direct wholly owned subsidiary, NRG Yield Operating LLC, are parties to a senior secured revolving credit facility, which can be used for cash and for the issuance of letters of credit. At March 31, 2018 , there was $67 million of letters of credit issued under the revolving credit facility and outstanding borrowings of $75 million on the revolver. On April 30, 2018, NRG Yield LLC and NRG Yield Operating LLC refinanced the revolving credit facility, which extended the maturity of the facility to April 28, 2023, and decreased the overall cost of borrowing from L+ 2.50% to L+ 1.75% . Project Financings Agua Caliente Project Financing On February 17, 2017, Agua Caliente Borrower 1 LLC and Agua Caliente Borrower 2 LLC, or Agua Caliente Holdco, the indirect owners of 51% of the Agua Caliente solar facility, issued $130 million of senior secured notes under the Agua Caliente Holdco Financing Agreement, or 2038 Agua Caliente Holdco Notes, that bear interest at 5.43% and mature on December 31, 2038. As described in Note 3 , Discontinued Operations and Dispositions , on March 27, 2017, NRG Yield, Inc. acquired Agua Caliente Borrower 2 LLC from NRG. The debt is joint and several with respect to Agua Caliente Borrower 1 LLC and Agua Caliente Borrower 2 LLC and is secured by the equity interests of each borrower in the Agua Caliente solar facility. Carlsbad Project Financing On May 26, 2017, Carlsbad Energy Holdings, LLC entered into a note payable agreement with financial institutions for the issuance of up to $407 million of senior secured notes that bear interest at a rate of 4.12% , and mature on October 31, 2038, and a credit agreement for a $194 million construction loan, that will convert to a term loan upon completion of the project as well as a letter of credit facility with an aggregate principal amount not to exceed $83 million , and a working capital loan facility with an aggregate principal amount not to exceed $4 million . As of March 31, 2018 , $475 million was outstanding under both the note and the construction loan.

Variable Interest Entities, or

Variable Interest Entities, or VIEs	3 Months Ended
	Mar. 31, 2018
Variable Interest Entities Disclosure [Abstract]
Variable Interest Entities, or VIEs	Variable Interest Entities, or VIEs Entities that are not Consolidated NRG has interests in entities that are considered VIEs under ASC 810, Consolidation , but NRG is not considered the primary beneficiary. NRG accounts for its interests in these entities under the equity method of accounting. Utility-Scale Solar Portfolio — Through its consolidated subsidiary, NRG Yield, Inc., the Company has equity interests in Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC which are accounted for as equity method investments as the Company does not have a controlling financial interest. The assets have 20 -year PPAs with PacifiCorp. NRG's maximum exposure to loss is limited to its equity investment, which was $338 million as of March 31, 2018 . GenConn Energy LLC — Through its consolidated subsidiary, NRG Yield, Inc., the Company owns a 50% interest in GCE Holding LLC, the owner of GenConn, which owns and operates two 190 MW peaking generation facilities in Connecticut at NRG's Devon and Middletown sites. NRG's maximum exposure to loss is limited to its equity investment, which was $100 million as of March 31, 2018 . Entities that are Consolidated The Company has a controlling financial interest in certain entities which have been identified as VIEs under ASC 810. These arrangements are primarily related to tax equity arrangements entered into with third-parties in order to finance the cost of solar energy systems under operating leases and wind facilities eligible for certain tax credits as further described in Note 2 , Summary of Significant Accounting Policies to the Company's 2017 Form 10-K. For one of the tax equity arrangements, the Company has a deficit restoration obligation equal to $81 million as of March 31, 2018 , which would be required to be funded if the arrangement were to be dissolved. The summarized financial information for the Company's consolidated VIEs consisted of the following: (In millions) March 31, 2018 December 31, 2017 Current assets $ 171 $ 118 Net property, plant and equipment 2,712 2,337 Other long-term assets 665 658 Total assets 3,548 3,113 Current liabilities 111 96 Long-term debt 856 661 Other long-term liabilities 211 209 Total liabilities 1,178 966 Redeemable noncontrolling interest 80 78 Noncontrolling interests 646 507 Net assets less noncontrolling interests $ 1,644 $ 1,562

Changes in Capital Structure

Changes in Capital Structure	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Changes in Capital Structure	Changes in Capital Structure As of March 31, 2018 and December 31, 2017 , the Company had 500,000,000 shares of common stock authorized. The following table reflects the changes in NRG's common stock issued and outstanding: Issued Treasury Outstanding Balance as of December 31, 2017 418,323,134 (101,580,045 ) 316,743,089 Shares issued under LTIPs 1,081,994 — 1,081,994 Shares issued under ESPP — 175,862 175,862 Shares repurchased — (3,114,748 ) (3,114,748 ) Balance as of March 31, 2018 419,405,128 (104,518,931 ) 314,886,197 Employee Stock Purchase Plan In January 2018, 175,862 shares of common stock were issued to employee accounts from treasury stock for the offering period of July 1, 2017 to December 31, 2017. In January 2018, NRG suspended the ESPP. Share Repurchases In February 2018, the Company's board of directors authorized the Company to repurchase $1 billion of its common stock, with the first $500 million program beginning as soon as permitted. In March 2018 , share repurchases were made as follows: Total number of shares purchased Average price paid per share (a) Amounts paid for shares purchased (in millions) (a) Board Authorized Share Repurchases March 2018 3,114,748 $ 29.75 $ 93 (a) The average price paid per share and amounts paid for shares purchased exclude the commissions of $0.01 per share paid in connection with the share repurchase. NRG Common Stock Dividends The following table lists the dividends paid during the three months ended March 31, 2018 : First Quarter 2018 Dividends per Common Share $ 0.03 On April 19, 2018 , NRG declared a quarterly dividend on the Company's common stock of $0.03 per share, payable May 15, 2018 , to stockholders of record as of May 1, 2018 , representing $0.12 per share on an annualized basis. The Company's common stock dividends are subject to available capital, market conditions, and compliance with associated laws, regulations and other contractual obligations.

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company's segment structure reflects how management currently makes financial decisions and allocates resources. The Company's businesses are segregated as follows: Generation, which includes generation, international and BETM; Retail, which includes Mass customers and Business Solutions, which includes C&I customers and other distributed and reliability products; Renewables, which includes solar and wind assets, excluding those in NRG Yield; NRG Yield; and corporate activities. During 2017, NRG Yield acquired several projects totaling 555 MW from NRG. On March 30, 2018, the Company sold to NRG Yield, Inc. 100% of NRG's interests in Buckthorn Renewables, LLC, which owns a 154 MW construction-stage utility-scale solar generation project, located in Texas. These acquisitions were treated as a transfer of entities under common control and accordingly, all historical periods have been recast to reflect the acquisition as if they had occurred at the beginning of the financial statement period. On June 14, 2017, as described in Note 3 , Discontinued Operations and Dispositions , NRG deconsolidated GenOn for financial reporting purposes. The financial information for all historical periods have been recast to reflect the presentation of GenOn as discontinued operations within the corporate segment. NRG’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, free cash flow and capital for allocation, as well as net income/(loss). Retail (a) Generation (a) Renewables (a) NRG Yield Corporate (a) Eliminations Total Three months ended March 31, 2018 (In millions) Operating revenues (a) $ 1,481 $ 327 $ 86 $ 225 $ 2 $ 300 $ 2,421 Depreciation and amortization 28 67 51 81 8 — 235 Reorganization costs 3 4 — — 13 — 20 Equity in earnings/(losses) of unconsolidated affiliates — 2 — 4 (1 ) (7 ) (2 ) Income/(loss) from continuing operations before income taxes 946 (536 ) (40 ) (1 ) (126 ) (11 ) 232 Income/(loss) from continuing operations 946 (536 ) (34 ) — (132 ) (11 ) 233 Net Income/(Loss) 946 (536 ) (34 ) — (132 ) (11 ) 233 Net Income/(Loss) attributable to NRG Energy, Inc. $ 940 $ (536 ) $ 1 $ 21 — $ (148 ) $ 1 $ 279 Total assets as of March 31, 2018 $ 3,521 $ 7,313 $ 5,191 $ 8,362 $ 9,108 $ (9,743 ) $ 23,752 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 1 $ (307 ) $ 8 $ — $ (2 ) $ — $ (300 ) Retail (a) Generation (a) Renewables (a) NRG Yield Corporate (a)(b) Eliminations Total Three months ended March 31, 2017 (In millions) Operating revenues (a) $ 1,335 $ 965 $ 95 $ 221 $ 10 $ (244 ) $ 2,382 Depreciation and amortization 28 97 47 77 8 — 257 Equity in (losses)/earnings of unconsolidated affiliates — (13 ) — 19 3 (4 ) 5 (Loss)/income from continuing operations before income taxes (31 ) 37 (35 ) (3 ) (137 ) (4 ) (173 ) (Loss)/income from continuing operations (34 ) 37 (29 ) (2 ) (137 ) (4 ) (169 ) Loss from discontinued operations, net of tax — — — — (34 ) — (34 ) Net (Loss)/Income (34 ) 37 (29 ) (2 ) (171 ) (4 ) (203 ) Net (Loss)/Income attributable to NRG Energy, Inc. $ (33 ) $ 37 $ (1 ) $ 12 $ (171 ) $ (7 ) $ (163 ) (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 1 $ 209 $ 8 $ — $ 26 $ — $ 244 (b) Includes other income - affiliate $ — $ — $ — $ — $ 48 $ — $ 48

Earnings_(Loss) Per Share

Earnings/(Loss) Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings/(Loss) Per Share	Earnings/(Loss) Per Share Basic earnings/(loss) per common share is computed by dividing net income/(loss) less accumulated preferred stock dividends by the weighted average number of common shares outstanding. Shares issued and treasury shares repurchased during the year are weighted for the portion of the year that they were outstanding. Diluted earnings/(loss) per share is computed in a manner consistent with that of basic income/(loss) per share while giving effect to all potentially dilutive common shares that were outstanding during the period. The reconciliation of NRG's basic and diluted loss per share is shown in the following table: Three months ended March 31, (In millions, except per share data) 2018 2017 Basic income/(loss) per share attributable to NRG Energy, Inc. common stockholders Net income/(loss) attributable to NRG Energy, Inc. $ 279 $ (163 ) Weighted average number of common shares outstanding - basic 318 316 Earnings/(loss) per weighted average common share — basic $ 0.88 $ (0.52 ) Diluted income/(loss) per share attributable to NRG Energy, Inc. common stockholders Weighted average number of common shares outstanding - diluted 318 316 Incremental shares attributable to the issuance of equity compensation (treasury stock method) 4 — Total dilutive shares 322 316 Earnings/(loss) per weighted average common share — diluted $ 0.87 $ (0.52 ) The following table summarizes NRG’s outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company’s diluted loss per share: Three months ended March 31, (In millions of shares) 2018 2017 Equity compensation plans 1 6 Total 1 6

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Effective Tax Rate The income tax provision consisted of the following: Three months ended March 31, (In millions except otherwise noted) 2018 2017 Income/(Loss) before income taxes $ 232 $ (173 ) Income tax benefit from continuing operations (1 ) (4 ) Effective tax rate (0.4 )% 2.3 % For the three months ended March 31, 2018 , NRG's overall effective tax rate was different than the statutory rate of 21% primarily due to the tax benefit for the change in valuation allowance, the generation of PTCs from various wind facilities and the inclusion of consolidated partnerships partially offset by current state tax expense. For the three months ended March 31, 2017 , NRG's overall effective tax rate was different than the statutory rate of 35% primarily due to the change in valuation allowance partially offset by the generation of PTCs and ITCs from various wind and solar facilities, respectively and current state tax expense. Uncertain Tax Benefits As of March 31, 2018 , NRG has recorded a non-current tax liability of $35 million for uncertain tax benefits from positions taken on various state income tax returns, including accrued interest. For the three months ended March 31, 2018 , NRG accrued an immaterial amount of interest relating to the uncertain tax benefits. As of March 31, 2018 , NRG had cumulative interest and penalties related to these uncertain tax benefits of $3 million . The Company recognizes interest and penalties related to uncertain tax benefits in income tax expense. NRG is subject to examination by taxing authorities for income tax returns filed in the U.S. federal jurisdiction and various state and foreign jurisdictions including operations located in Australia. The Company is no longer subject to U.S. federal income tax examinations for years prior to 2015. The Company is no longer subject to U.S. federal income tax examinations for years prior to 2015. With few exceptions, state and local income tax examinations are no longer open for years before 2010.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Services Agreement and Transition Services Agreement with GenOn The Company provides GenOn with various management, personnel and other services, which include human resources, regulatory and public affairs, accounting, tax, legal, information systems, treasury, risk management, commercial operations, and asset management, as set forth in the services agreement with GenOn, or the Services Agreement. The initial term of the Services Agreement was through December 31, 2013, with an automatic renewal absent a request for termination. The fee charged was determined based on a fixed amount as described in the Services Agreement and was calculated based on historical GenOn expenses prior to the NRG Merger. The annual fees under the Services Agreement were approximately $193 million and management has concluded that this method of charging overhead costs is reasonable. As described in Note 3, Discontinued Operations and Dispositions , in connection with the Restructuring Support Agreement, NRG agreed to provide shared services to GenOn under the Services Agreement for an adjusted annualized fee of $84 million . In December 2017, in conjunction with the confirmation of the GenOn Entities' plan of reorganization, the Services Agreement was terminated and replaced by the transition services agreement. Under the transition services agreement, NRG will continue to provide the shared services and other separation services at an annualized rate of $84 million , subject to certain credits and adjustments, until September 30, 2018, which GenOn can terminate earlier if NRG is provided 60 days' notice. NRG may provide additional separation services that are necessary for or reasonably related to the operation of GenOn's business after such date, subject to NRG's prior written consent, not to be unreasonably withheld. For the three months ended March 31, 2018 , NRG recorded approximately $21 million against selling, general and administrative expenses post-Chapter 11 Filing. For the three months ended March 31, 2017 , NRG recorded other income - affiliate related to these services of $48 million . In addition, as described in Note 3 , Discontinued Operations and Dispositions , under the Restructuring Support Agreement, NRG has agreed to provide GenOn with a $28 million credit against amounts owed to NRG under the transition services agreement. The credit is intended to reimburse GenOn for its payment of financing costs. Any unused amount can be paid in cash at GenOn's request, subject to the terms and conditions of the transition services agreement. Credit Agreement with GenOn NRG and GenOn are party to a secured intercompany revolving credit agreement. The intercompany revolving credit agreement provided for a $500 million revolving credit facility, all of which was available for revolving loans and letters of credit. At March 31, 2018 and December 31, 2017 , $86 million and $92 million , respectively, of letters of credit were issued and outstanding under the NRG credit agreement for GenOn. Additionally, as of March 31, 2018 and December 31, 2017 , there were $125 million of loans outstanding under the intercompany secured revolving credit facility, which will be applied against the settlement cash consideration that will be paid to GenOn upon emergence from bankruptcy, as further discussed in Note 3 , Discontinued Operations and Dispositions . In addition, the intercompany secured revolving credit facility contains customary covenants and events of default. As of March 31, 2018 , GenOn was in default under the secured intercompany revolving credit agreement due to the filing of the Chapter 11 Cases. As a result of the Chapter 11 Cases, no additional revolving loans or letters of credit are available to GenOn. Effective with completion of the reorganization, GenOn must repay NRG for all revolving loans outstanding, with such amount to be netted against the settlement payment owed from NRG to GenOn. Accordingly, the affiliate receivable is recorded net within accrued expenses and other current liabilities - affiliate on the consolidated balance sheet as of March 31, 2018 , all of which is to be settled at emergence. Interest continues to accrue during the pendency of the Chapter 11 Cases and borrowings remain secured obligations. Commercial Operations Agreement NRG Power Marketing LLC has entered into physical and financial intercompany commodity and hedging transactions with GenOn and certain of its subsidiaries. Subject to applicable collateral thresholds, these arrangements may provide for the bilateral exchange of credit support based upon market exposure and potential market movements. The terms and conditions of the agreements are generally consistent with industry practices and other third party arrangements. As of March 31, 2018 , derivative assets and liabilities associated with these transactions are recorded within NRG's derivative instruments balances on the consolidated balance sheet, with related revenues and costs within operating revenues and cost of operations, respectively. Additionally, as of March 31, 2018 and December 31, 2017 , the Company had $28 million and $32 million , respectively, of cash collateral posted in support of energy risk management activities by GenOn. NRG will provide settlement cash consideration to GenOn of $261.3 million , which will be paid in cash less any amounts owed to NRG under the intercompany secured revolving credit facility.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies This footnote should be read in conjunction with the complete description under Note 22 , Commitments and Contingencies , to the Company's 2017 Form 10-K. Commitments First Lien Structure NRG has granted first liens to certain counterparties on a substantial portion of the Company's assets, excluding assets acquired in the GenOn and EME (including Midwest Generation) acquisitions, assets held by NRG Yield, Inc. and NRG's assets that have project-level financing, to reduce the amount of cash collateral and letters of credit that it would otherwise be required to post from time to time to support its obligations under out-of-the-money hedge agreements for forward sales of power or MWh equivalents. The Company's lien counterparties may have a claim on NRG's assets to the extent market prices exceed the hedged price. As of March 31, 2018 , hedges under the first lien were in-the-money for NRG on a counterparty aggregate basis. Contingencies 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. NRG 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 has assessed each of the following matters based on current information and made a judgment concerning its potential outcome, considering the nature of the claim, the amount and nature of damages sought, and the probability of success. Unless specified below, the Company is unable to predict the outcome of these legal proceedings 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, NRG 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 NRG's consolidated financial position, results of operations, or cash flows. Midwest Generation Asbestos Liabilities — The Company, through its subsidiary, Midwest Generation, may be subject to potential asbestos liabilities as a result of its acquisition of EME. The Company is currently analyzing the scope of potential liability as it may relate to Midwest Generation. The Company believes that it has established an adequate reserve for these cases. On March 27, 2018, ComEd filed a Motion to Compel Payments of Claims seeking $61 million related to asbestos liabilities. On April 25, 2018, NRG filed an Omnibus Objection to All Remaining Claims of ComEd and Exelon. Midwest Generation New Source Review Litigation — In August 2009, the EPA and the Illinois Attorney General, or the Government Plaintiffs, filed a complaint, or the Governments’ Complaint, in the U.S. District Court for the Northern District of Illinois alleging violations of CAA PSD requirements by Midwest Generation arising from maintenance, repair or replacement projects at six Illinois coal-fired electric generating stations performed by Midwest Generation or ComEd, a prior owner of the stations, including alleged failures to obtain PSD construction permits and to comply with BACT requirements. The Government Plaintiffs also alleged violations of opacity and PM standards at the Midwest Generation plants. Finally, the Government Plaintiffs alleged that Midwest Generation violated certain operating permit requirements under Title V of the CAA allegedly arising from such claimed PSD, opacity and PM emission violations. Several environmental groups intervened as plaintiffs in this litigation and filed a complaint, or the Intervenors’ Complaint, which alleged opacity, PM and related Title V violations. Midwest Generation filed a motion to dismiss nine of the ten PSD counts in the Governments’ Complaint, and to dismiss the tenth PSD count to the extent the Governments’ Complaint sought civil penalties for that count. The trial court granted the motion in March 2010. In June 2010, the Government Plaintiffs and Intervenors each filed an amended complaint. The Governments’ Amended Complaint again alleged that Midwest Generation violated PSD (based upon the same projects as alleged in their original complaint, but adding allegations that the Company was liable as the “successor” to ComEd), Title V and opacity and PM standards. It named EME and ComEd as additional defendants and alleged PSD violations (again, premised on the same projects) against them. The Intervenors’ Amended Complaint named only Midwest Generation as a defendant and alleged Title V and opacity/PM violations, as well as one of the ten PSD violations alleged in the Governments’ Amended Complaint. Midwest Generation again moved to dismiss all but one of the Government Plaintiffs’ PSD claims and the related Title V claims. Midwest Generation also filed a motion to dismiss the PSD claim in the Intervenors’ Amended Complaint and the related Title V claims. In March 2011, the trial court granted Midwest Generation’s partial motion to dismiss the Government Plaintiffs’ PSD claims. The trial court denied Midwest Generation’s motion to dismiss the PSD claim asserted in the Intervenors’ Amended Complaint, but noted that the plaintiffs would be required to convince the court that the statute of limitations should be equitably tolled. The trial court did not address other counts in the amended complaints that allege violations of opacity and PM emission limitations under the Illinois State Implementation Plan and related Title V claims. The trial court also granted the motions to dismiss the PSD claims asserted against EME and ComEd. Following the trial court ruling, the Government Plaintiffs appealed the trial court’s dismissals of their PSD claims, including the dismissal of nine of the ten PSD claims against Midwest Generation and of the PSD claims against the other defendants. Those PSD claim dismissals were affirmed by the U.S. Court of Appeals for the Seventh Circuit in July 2013. In addition, in 2012, all but one of the environmental groups that had intervened in the case dismissed their claims without prejudice. As a result, only one environmental group remains a plaintiff intervenor in the case. On March 9, 2018, the Consent Decree which provides that Midwest Generation will be required to (x) pay $500,000 to each of the State of Illinois and the Federal Government and (y) make and maintain certain operational improvements was lodged with the court. Telephone Consumer Protection Act Purported Class Actions — Three purported class action lawsuits have been filed against NRG Residential Solar Solutions, LLC — one in California and two in New Jersey. The plaintiffs generally allege misrepresentation by the call agents and violations of the TCPA, claiming that the defendants engaged in a telemarketing campaign placing unsolicited calls to individuals on the “Do Not Call List.” The plaintiffs seek statutory damages of up to $1,500 per plaintiff, actual damages and equitable relief. On June 22, 2017, plaintiffs in the California case filed a motion for leave to file a second amended complaint to substitute new plaintiffs. Defendants filed an opposition to this motion on June 26, 2017. The court granted plaintiffs' motion to substitute new plaintiffs and on August 1, 2017, defendants filed an answer to the second amended complaint. On August 31, 2017, the court in the California case agreed that the litigation should be stayed pending final court approval of the New Jersey settlement. On July 12, 2017, the parties in the New Jersey action reached an agreement in principle to resolve the class allegations which was confirmed by a term sheet signed by the parties on July 28, 2017. On September 27, 2017, plaintiffs in the New Jersey case filed their motion for preliminary approval of the class settlement which was approved by the court on November 17, 2017. On May 1, 2018, the court granted plaintiffs' motion for final approval of the class action settlement. California Department of Water Resources and San Diego Gas & Electric Company v. Sunrise Power Company LLC — On January 29, 2016, CDWR and SDG&E filed a lawsuit against Sunrise Power Company, along with NRG and Chevron Power Corporation. In June 2001, CDWR and Sunrise entered into a 10 -year PPA under which Sunrise would construct and operate a generating facility and provide power to CDWR. At the time the PPA was entered into, Sunrise had a transportation services agreement, or TSA, to purchase natural gas from Kern River through April 30, 2018. In August 2003, CDWR entered into an agreement with Sunrise and Kern River in which CDWR accepted assignment of the TSA through the term of the PPA. After the PPA expired, Kern River demanded that any reassignment be to a party which met certain creditworthiness standards which Sunrise did not. As such, the plaintiffs brought this lawsuit against the defendants alleging breach of contract, breach of covenant of good faith and fair dealing and improper distributions. Plaintiffs generally claim damages of $1.2 million per month for the remaining 70 months of the TSA. On April 20, 2016, the defendants filed objections in response to the plaintiffs' complaint. The objections were granted on June 14, 2016; however, the plaintiffs were allowed to file amended complaints on July 1, 2016. On July 27, 2016, defendants filed objections to the amended complaints. On November 18, 2016, the court sustained the objections and allowed plaintiffs another opportunity to file a second amended lawsuit which they did on January 13, 2017. On April 21, 2017, the court issued an order sustaining the objections without leave to amend. On July 14, 2017, CDWR filed a notice of appeal. On January 10, 2018, CDWR filed its appellate brief. Defendants filed their opposition brief on April 10, 2018. 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, CA. 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. The case is currently stayed by agreement of the parties. On May 2, 2018, the court approved a joint stipulation which provides: (i) plaintiffs' opposition brief is due on or before July 30, 2018; (ii) defendants' reply brief is due on or before October 5, 2018; and (iii) a hearing on the motions is scheduled on October 30, 2018. Griffoul v. NRG Residential Solar Solutions — On February 28, 2017, plaintiffs, consisting of New Jersey residential solar customers, filed a purported class action lawsuit in New Jersey state court. Plaintiffs allege violations of the New Jersey Consumer Fraud Action and Truth-in-Consumer Contracts, Warranty and Notice Act with regard to certain provisions of their residential solar contracts. The plaintiffs seek damages and injunctive relief as to the proper allocation of the solar renewable energy credits. On June 6, 2017, the defendants filed a motion to compel arbitration or dismiss the lawsuit. Plaintiffs filed their opposition on June 29, 2017. On July 14, 2017, the court denied NRG's motion to compel arbitration or dismiss the case. On July 25, 2017, NRG filed a motion for reconsideration of the appeal, which was denied. On August 22, 2017, NRG filed a notice of appeal. After fully briefing the appeal, oral argument was heard on April 24, 2018. Rice v. NRG — On April 14, 2017, plaintiffs filed a purported class action lawsuit in the U.S. District Court for the Western District of Pennsylvania against NRG, First Energy Corporation and Matt Canastrale Contracting, Inc. Plaintiffs generally claim personal injury, trespass, nuisance and property damage related to the disposal of coal ash from GenOn's Elrama Power Plant and First Energy’s Mitchell and Hatfield Power Plants. Plaintiffs generally seek monetary damages, medical monitoring and remediation of their property. Plaintiffs filed an amended complaint on August 14, 2017. On October 20, 2017, NRG filed its answers and affirmative defenses. Washington-St. Tammany and Claiborne Electric Cooperative v. LaGen — On June 28, 2017, plaintiffs Washington-St. Tammany Electric Cooperative, Inc. and Claiborne Electric Cooperative, Inc. filed a lawsuit against Louisiana Generating, L.L.C., or LaGen, in the United States District Court for the Middle District of Louisiana. The plaintiffs claim breach of contract against LaGen for allegedly improperly charging the plaintiffs for costs related to the installation and maintenance of certain pollution control technology. Plaintiffs seek damages for the alleged improper charges and a declaration as to which charges are proper under the contract. On September 14, 2017, the court issued a scheduling order setting this case for trial on October 21, 2019. LaGen filed its answer and affirmative defenses on November 17, 2017. GenOn Chapter 11 Cases — On the Petition Date, the GenOn Entities filed voluntary petitions for relief under Chapter 11 of the Bankruptcy Code in the Bankruptcy Court. Under the Restructuring Support Agreement to which the GenOn Entities, NRG and certain of GenOn's and GenOn Americas Generation's senior unsecured noteholders are parties, each of them supported the Bankruptcy Court's approval of the plan of reorganization. GenOn has a customary "fiduciary out" under the Restructuring Support Agreement. If the plan of reorganization is not consummated, NRG may not be entitled to the benefits of the Settlement Agreement provided under the Restructuring Support Agreement and it will remain subject to any claims of GenOn and the noteholders, including claims relating to or arising out of any shared services and any other relationships or transactions between the companies. See Note 3 , Discontinued Operations and Dispositions , for additional information related to the Chapter 11 Cases. 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. 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. Plaintiffs generally seek return of all monies paid under the Services Agreement and any other damages that the court deems appropriate. On February 3, 2017, the court entered an order approving a Standstill Agreement whereby the parties agreed to suspend all deadlines in the case until March 1, 2017. The Standstill Agreement terminated on March 1, 2017. On April 30, 2017, the Noteholders filed an amended complaint that asserts (i) additional fraudulent transfer claims in relation to GenOn’s sale of the Marsh Landing project to NRG Yield LLC, (ii) alleged breaches of fiduciary duty by certain current and former officers and directors of GenOn in relation to the Services Agreement and the alleged usurpation of corporate opportunities concerning the Mandalay and Canal projects and (iii) claims against NRG for allegedly aiding and abetting such claimed breaches 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 December 14, 2017, a settlement agreement was executed between GenOn and NRG which should ultimately resolve this lawsuit. Morgantown v. GenOn Mid-Atlantic — On June 8, 2017, Morgantown and Dickerson Owner Lessors filed a lawsuit against GenOn Mid-Atlantic, LLC, NRG North America LLC, GenOn Americas Generation, LLC, NRG Americas, Inc., GenOn Energy Holdings, Inc., GenOn Energy, Inc., and NRG Energy, Inc. in New York State Supreme Court. The plaintiffs allege that they were overcharged by defendants for certain services outlined in a Services Agreement and that defendants caused a Qualified Credit Support portion of a Participation Agreement, or QCS Agreement, to be violated by causing the transfer of certain money outside the allowable confines set forth in the QCS Agreement. In addition, plaintiffs claim that the transfers were unfairly executed and done so in an effort to defraud plaintiffs and hinder their ability to continue to do business. As such, plaintiffs seek, among other things, the return of certain transferred funds and service charges paid and to bar defendants from executing additional transfers on plaintiffs’ behalf. On November 7, 2017, the Bankruptcy Court issued an order estimating the claims to be valued at $0 . On December 14, 2017, a settlement agreement was executed between GenOn and NRG. On April 27, 2018, the parties executed a mutual release which in conjunction with the settlement agreement resolved this lawsuit. BTEC v. NRG Texas Power — On July 18, 2017, BTEC New Albany LLC, or BTEC, filed a lawsuit against NRG Texas Power LLC, or NRG Texas Power, in the Harris County District Court in Texas. On January 15, 2013, the parties entered into a Membership Interest and Purchase Agreement, or MIPA, whereby BTEC agreed to dismantle, transport and rebuild an electric power generation facility at the former P.H. Robinson Electric Generating Station in Bacliff, Texas. The MIPA required BTEC to meet a Guaranteed Commercial Completion Date of May 31, 2016. But even a year later, BTEC had not satisfied all of the contractually-required acceptance criteria. As a result and given that the MIPA expiration date passed on May 31, 2017, NRG elected to terminate the contract in June 2017. BTEC claims that NRG Texas Power breached the MIPA by improperly terminating it, and seeks a declaratory judgment as to the rights and obligations of the parties. In addition, BTEC seeks damages, interest and attorney’s fees. On August 14, 2017, NRG Texas Power served its answer to the lawsuit. On September 7, 2017, NRG Texas Power filed a counterclaim seeking damages in excess of $48 million . On March 21, 2018, BTEC filed a Second Amended Petition in which they supplemented their previous claims and added a claim for specific performance. GenOn Related Contingencies Actions Pursued by MC Asset Recovery — With Mirant Corporation's emergence from bankruptcy protection in 2006, certain actions filed by GenOn Energy Holdings and some of its subsidiaries against third parties were transferred to MC Asset Recovery, a wholly owned subsidiary of GenOn Energy Holdings. MC Asset Recovery is governed by a manager who is independent of NRG and GenOn. MC Asset Recovery is a disregarded entity for income tax purposes. Under the remaining action transferred to MC Asset Recovery, MC Asset Recovery seeks to recover damages from Commerzbank AG and various other banks, or the Commerzbank Defendants, for alleged fraudulent transfers that occurred prior to Mirant's bankruptcy proceedings. In December 2010, the U.S. District Court for the Northern District of Texas dismissed MC Asset Recovery's complaint against the Commerzbank Defendants. In January 2011, MC Asset Recovery appealed the District Court's dismissal of its complaint against the Commerzbank Defendants to the U.S. Court of Appeals for the Fifth Circuit, or the Fifth Circuit. In March 2012, the Fifth Circuit reversed the District Court's dismissal and reinstated MC Asset Recovery's amended complaint against the Commerzbank Defendants. On December 10, 2015, the District Court granted summary judgment in favor of the Commerzbank Defendants. On December 29, 2015, MC Asset Recovery filed a notice to appeal this judgment with the Fifth Circuit. On June 1, 2017, the Fifth Circuit affirmed the District Court's judgment. On June 12, 2017, MC Asset Recovery petitioned the Fifth Circuit for rehearing. The petition for rehearing was denied and a court order and judgment affirming the District Court's judgments was entered on July 17, 2017. The bankruptcy court is scheduled to hear a Motion for a Final Decree in the Mirant bankruptcy on June 13, 2018. Natural Gas Litigation — GenOn is party to several lawsuits, certain of which are class action lawsuits, in state and federal courts in Kansas, Missouri, Nevada and Wisconsin. These lawsuits were filed in the aftermath of the California energy crisis in 2000 and 2001 and the resulting FERC investigations and relate to alleged conduct to increase natural gas prices in violation of state antitrust law and similar laws. The lawsuits seek treble or punitive damages, restitution and/or expenses. The lawsuits also name as parties a number of energy companies unaffiliated with NRG. In July 2011, the U.S. District Court for the District of Nevada, which was handling four of the five cases, granted the defendants' motion for summary judgment and dismissed all claims against GenOn in those cases. The plaintiffs appealed to the U.S. Court of Appeals for the Ninth Circuit, or the Ninth Circuit, which reversed the decision of the District Court. GenOn along with the other defendants in the lawsuit filed a petition for a writ of certiorari to the U.S. Supreme Court challenging the Ninth Circuit's decision and the U.S. Supreme Court granted the petition. On April 21, 2015, the U.S. Supreme Court affirmed the Ninth Circuit’s holding that plaintiffs’ state antitrust law claims are not field-preempted by the federal Natural Gas Act and the Supremacy Clause of the U.S. Constitution. The U.S. Supreme Court left open whether the claims were preempted on the basis of conflict preemption. The U.S. Supreme Court directed that the case be remanded to the U.S. District Court for the District of Nevada for further proceedings. On March 7, 2016, class plaintiffs filed their motions for class certification. On March 30, 2017, the court denied the plaintiffs' motions for class certification. On April 13, 2017, the plaintiffs petitioned the Ninth Circuit for interlocutory review of the court’s order denying class certification. On June 13, 2017, the Ninth Circuit granted plaintiffs' petition for interlocutory review. The appeal is fully briefed. In May 2016 in one of the Kansas cases, the U.S. District Court for the District of Nevada granted the defendants' motion for summary judgment. Subsequently in December 2016, the plaintiffs filed a notice of appeal with the Ninth Circuit. The appeal was argued on February 16, 2018. On March 27, 2018, the Ninth Circuit reversed the District Court's decision. On April 10, 2018, the defendants filed a petition for rehearing. GenOn has agreed to indemnify CenterPoint against certain losses relating to these lawsuits. In September 2012, the State of Nevada Supreme Court, which was handling the remaining case, affirmed dismissal by the Eighth Judicial District Court for Clark County, Nevada of all plaintiffs' claims against GenOn. In February 2013, the plaintiffs in the Nevada case filed a petition for a writ of certiorari to the U.S. Supreme Court. In June 2013, the U.S. Supreme Court denied the petition for a writ of certiorari, thereby ending one of the five lawsuits. On February 26, 2018, GenOn filed objections to the proofs of claim filed in the Chapter 11 Cases by all of the plaintiffs in each of the four cases. GenOn filed that same day a motion seeking a schedule for a series of hearings to resolve the objections and asking the Bankruptcy Court to estimate all of the proofs of claim at zero dollars. The plaintiffs have objected to the request for Bankruptcy Court to estimate the proofs of claim. The Bankruptcy Court ordered briefing as to whether it had authority to resolve these claims. Potomac River Environmental Investigation — In March 2013, NRG Potomac River LLC, a subsidiary of GenOn, received notice that the District of Columbia Department of Environment (now renamed the Department of Energy and Environment, or DOEE) was investigating potential discharges to the Potomac River originating from the Potomac River Generating facility site, a site where the generation facility is no longer in operation. In connection with that investigation, DOEE served a civil subpoena on NRG Potomac River LLC requesting information related to the site and potential discharges occurring from the site. NRG Potomac River LLC provided various responsive materials. In January 2016, DOEE advised NRG Potomac River LLC that DOEE believed various environmental violations had occurred as a result of discharges DOEE believes occurred to the Potomac River from the Potomac River Generating facility site and as a result of associated failures to accurately or sufficiently report such discharges. DOEE has indicated it believes that penalties are appropriate in light of the violations. NRG Potomac River LLC is currently reviewing the information provided by DOEE. Natixis v. GenOn Mid-Atlantic — On February 16, 2018, Natixis Funding Corp. and Natixis, New York Branch filed a complaint in the Supreme Court of the State of New York against GenOn Mid-Atlantic, the owner lessors under GenOn Mid-Atlantic’s operating leases of the Dickerson and Morgantown coal generation units, and the lease indenture trustee under those leases. The plaintiffs’ allegations against GenOn Mid-Atlantic relate to a payment agreement between GenOn Mid-Atlantic and Natixis Funding Corp. to procure credit support for the payment of certain lease payments owed pursuant to the GenOn Mid-Atlantic operating leases for Morgantown and Dickerson. The plaintiffs seek approximately $34 million in damages arising from GenOn Mid-Atlantic’s purported breach of certain warranties in the payment agreement. On April 2, 2018, GenOn Mid-Atlantic removed the allegations against it to the U.S. District Court for the Southern District of New York. On April 11, 2018, the U.S. District Court for the Southern District of New York entered a briefing schedule on a forthcoming motion to remand by Natixis Funding Corp. and a forthcoming motion to transfer by GenOn Mid-Atlantic.

Regulatory Matters

Regulatory Matters	3 Months Ended
	Mar. 31, 2018
Regulatory Matters Disclosure [Abstract]
Regulatory Matters	Regulatory Matters This footnote should be read in conjunction with the complete description under Note 23 , Regulatory Matters , to the Company's 2017 Form 10-K. NRG operates in a highly regulated industry and is subject to regulation by various federal and state agencies. As such, NRG is affected by regulatory developments at both the federal and state levels and in the regions in which NRG operates. In addition, NRG is subject to the market rules, procedures, and protocols of the various ISO and RTO markets in which NRG participates. These power markets are subject to ongoing legislative and regulatory changes that may impact NRG's wholesale and retail businesses. In addition to the regulatory proceedings noted below, NRG and its subsidiaries are parties to other regulatory proceedings arising in the ordinary course of business or have other regulatory exposure. In management's opinion, the disposition of these ordinary course matters will not materially adversely affect NRG's consolidated financial position, results of operations, or cash flows. National Department of Energy Consideration of 202(c) and Defense Production Act — On March 29, 2018, FirstEnergy Solutions requested that the Department of Energy provide price supports for its coal and nuclear units by having the DOE issue an emergency must-run order under Section 202(c) of the Federal Power Act. A number of parties have filed comments with the DOE, including PJM, challenging the assertion that the FirstEnergy Solutions’ units are necessary for grid reliability. The DOE has not yet formally responded. Subsequently, Senator Manchin of West Virginia has requested that the Administration utilize the Defense Production Act to require coal and nuclear units to continue to operate. The assertion is that these plants are needed to maintain national security. No formal timeline for action on either proposal has been set by the Administration. Zero-Emission Credits for Nuclear Plants in Illinois — In 2016, Illinois enacted a Zero Emission Credit, or ZEC, program for selected nuclear units in Illinois. In total, the program directs over $2.5 billion over ten years to nuclear plants in Illinois that would otherwise retire. Pursuant to the legislation , the Illinois Power Agency, or IPA, conducts a competitive solicitation to procure ZECs, although both the Governor of Illinois and Exelon have already announced that the ZECs will be awarded to two Exelon-owned nuclear power plants in Illinois. These ZECs are out-of-market subsidies that threaten to artificially suppress market prices and interfere with the wholesale power market. On February 14, 2017, NRG, along with other companies, filed a complaint in the U.S. District Court for the Northern District of Illinois alleging that the state program is preempted by federal law and in violation of the dormant commerce clause. Another plaintiff group filed a similar complaint on the same day. Subsequently, on March 31, 2017, NRG, along with other companies, filed a motion for preliminary injunction. On April 10, 2017, Exelon, as an intervenor defendant, and State defendants filed motions to dismiss. On July 14, 2017, Defendants' motions to dismiss were granted. On July 17, 2017, NRG, along with other companies, filed a notice of appeal to the U.S. Court of Appeals for the Seventh Circuit. Briefing is complete. Oral argument was held on January 3, 2018, with supplemental briefs filed on January 26, 2018. On February 21, 2018, the Seventh Circuit invited the U.S. to file an amicus brief in the proceeding. Zero-Emission Credits for Nuclear Plants in New York — On August 1, 2016, the NYSPSC issued its Clean Energy Standard, or CES, which provided for ZECs which would provide more than $7.6 billion over 12 years in out-of-market subsidy payments to certain selected nuclear generating units in the state. These ZECs are out-of-market subsidies that threaten to artificially suppress market prices and interfere with the wholesale power market. On October 19, 2016, NRG, along with other companies, filed a complaint in the U.S. District Court for the Southern District of New York, challenging the validity of the NYSPSC action and the ZEC program. On March 29, 2017, the U.S. District Court heard oral arguments on a motion to dismiss filed by defendants. On July 25, 2017, the defendants' motions to dismiss were granted. On August 24, 2017, NRG, along with other plaintiff companies, filed a notice of appeal to the U.S. Court of Appeals for the Second Circuit. Briefing is complete. Oral argument took place on March 12, 2018. Department of Energy's Proposed Grid Resiliency Pricing Rule and Subsequent FERC Proceeding — On September 29, 2017, the Department of Energy issued a proposed rulemaking titled the "Grid Resiliency Pricing Rule." The rulemaking directs FERC to take action to reform the ISO/RTO markets to value certain reliability and resiliency attributes of electric generation resources. On October 2, 2017, FERC issued a notice inviting comments. On October 4, 2017, FERC staff issued a series of questions requesting commenters to address. On October 23, 2017, NRG filed comments encouraging FERC to act expeditiously to modernize energy and capacity markets in a manner compatible with robust competitive markets. On January 8, 2018, FERC terminated the proposed rulemaking and opened a new proceeding asking each ISO/RTO to address specific questions focused on grid resilience. On March 9, 2018, the ISOs/RTOs filed comments to the questions posed by FERC. East/West Montgomery County Station Power Tax — On December 20, 2013, NRG received a letter from Montgomery County, Maryland requesting payment of an energy tax for the consumption of station power at the Dickerson Facility over the previous three years. Montgomery County seeks payment in the amount of $22 million , which includes tax, interest and penalties. NRG disputed the applicability of the tax. On December 11, 2015, the Maryland Tax Court reversed Montgomery County's assessment. Montgomery County filed an appeal, and on February 2, 2017, the Montgomery County Circuit Court affirmed the decision of the tax court. On February 17, 2017, Montgomery County filed an appeal to the Court of Special Appeals of Maryland. On April 24, 2018, the Court of Special Appeals of Maryland affirmed the lower court's decision. Puente Power Project — On October 5, 2017, the California Energy Commission, or CEC, the agency responsible for permitting the Puente Power Project, issued a statement on behalf of the committee of two Commissioners overseeing the permitting process stating their intention to issue a proposed decision that would deny a permit for the Puente Power Project. On October 16, 2017, NRG filed a motion to suspend the permitting proceeding for at least six months, which was granted on November 3, 2017. On April 20, 2018, NRG filed a motion requesting an additional extension of the suspension period to coincide with the CPUC’s final decision on SCE’s application seeking approval of resources procured through its Moorpark RFO, or until June 30, 2019, whichever is sooner.

Environmental Matters

Environmental Matters	3 Months Ended
	Mar. 31, 2018
Environmental Matters Disclosure [Abstract]
Environmental Matters	Environmental Matters This footnote should be read in conjunction with the complete description under Note 24 , Environmental Matters , to the Company's 2017 Form 10-K. NRG is subject to a wide range of environmental laws in the development, construction, ownership and operation of projects. These laws generally require that governmental permits and approvals be obtained before construction and during operation of power plants. NRG is also subject to laws regarding the protection of wildlife, including migratory birds, eagles and threatened and endangered species. The electric generation industry has been facing requirements regarding GHGs, combustion byproducts, water discharge and use, and threatened and endangered species that have been put in place in recent years. However, under the current U.S. presidential administration, some of these rules are being reconsidered and reviewed. In general, future laws are expected to require the addition of emissions controls or other environmental controls or to impose certain restrictions on the operations of the Company's facilities, which could have a material effect on the Company's consolidated financial position, results of operations, or cash flows. Federal and state environmental laws generally have become more stringent over time, although this trend could slow or pause in the near term with respect to federal laws under the current U.S. presidential administration. The EPA finalized CSAPR in 2011, which was intended to replace CAIR in January 2012, to address certain states' obligations to reduce emissions so that downwind states can achieve federal air quality standards. In December 2011, the D.C. Circuit stayed the implementation of CSAPR and then vacated CSAPR in August 2012 but kept CAIR in place until the EPA could replace it. In April 2014, the U.S. Supreme Court reversed and remanded the D.C. Circuit's decision. In October 2014, the D.C. Circuit lifted the stay of CSAPR. In response, the EPA in November 2014 amended the CSAPR compliance dates. Accordingly, CSAPR replaced CAIR on January 1, 2015. On July 28, 2015, the D.C. Circuit held that the EPA had exceeded its authority by requiring certain reductions that were not necessary for downwind states to achieve federal standards. Although the D.C. Circuit kept the rule in place, the court ordered the EPA to revise the Phase 2 (or 2017) (i) SO 2 budgets for four states including Texas and (ii) ozone-season NOx budgets for 11 states including Maryland, New Jersey, New York, Ohio, Pennsylvania and Texas. On October 26, 2016, the EPA finalized the CSAPR Update Rule, which reduces future NOx allocations and discounts the current banked allowances to account for the more stringent 2008 Ozone NAAQS and to address the D.C. Circuit's July 2015 decision. This rule has been challenged in the D.C. Circuit. The Company believes its investment in pollution controls and cleaner technologies leave the fleet well-positioned for compliance. In February 2012, the EPA promulgated standards (the MATS rule) to control emissions of HAPs from coal and oil-fired electric generating units. The rule established limits for mercury, non-mercury metals, certain organics and acid gases, which had to be met beginning in April 2015 (with some units getting a 1-year extension). In June 2015, the U.S. Supreme Court issued a decision in the case of Michigan v. EPA, and held that the EPA unreasonably refused to consider costs when it determined that it was "appropriate and necessary" to regulate HAPs emitted by electric generating units. The U.S. Supreme Court did not vacate the MATS rule but rather remanded it to the D.C. Circuit for further proceedings. In December 2015, the D.C. Circuit remanded the MATS rule to the EPA without vacatur. On April 25, 2016, the EPA released a supplemental finding that the benefits of this regulation outweigh the costs to address the U.S. Supreme Court's ruling that the EPA had not properly considered costs. This finding has been challenged in the D.C. Circuit. On April 18, 2017, the EPA asked the D.C. Circuit to postpone oral argument that had been scheduled for May 18, 2017 because the EPA is closely reviewing the supplemental finding to determine whether it should reconsider all or part of the rule. On April 27, 2017, the D.C. Circuit granted EPA's request to postpone the oral argument and hold the case in abeyance. While NRG cannot predict the final outcome of this rulemaking, NRG believes that because it has already invested in pollution controls and cleaner technologies, the fleet is well-positioned to comply with the MATS rule. Water In August 2014, the EPA finalized the regulation regarding the use of water for once through cooling at existing facilities to address impingement and entrainment concerns. NRG anticipates that more stringent requirements will be incorporated into some of its water discharge permits over the next several years as NPDES permits are renewed. Effluent Limitations Guidelines — In November 2015, the EPA revised the Effluent Limitations Guidelines for Steam Electric Generating Facilities, which would have imposed more stringent requirements (as individual permits were renewed) for wastewater streams from flue gas desulfurization, or FGD, fly ash, bottom ash, and flue gas mercury control. In April 2017, the EPA granted two petitions to reconsider the rule and also administratively stayed some of the deadlines. On September 18, 2017, the EPA promulgated a final rule that (i) postpones the compliance dates to preserve the status quo for FGD wastewater and bottom ash transport water by two years to November 2020 until the EPA completes its next rulemaking and (ii) withdrew the April 2017 administrative stay. The legal challenges have been suspended while the EPA reconsiders and likely modifies the rule. Accordingly, the Company has largely eliminated its estimate of the environmental capital expenditures that would have been required to comply with permits incorporating the revised guidelines. The Company will revisit these estimates after the rule is revised. Byproducts, Wastes, Hazardous Materials and Contamination In April 2015, the EPA finalized the rule regulating byproducts of coal combustion (e.g., ash and gypsum) as solid wastes under the RCRA. On September 13, 2017, the EPA granted the petition for reconsideration that the Utility Solid Waste Activities Group filed in May 2017. The Company has evaluated the impact of the new rule on the Company's consolidated financial position, results of operations, or cash flows and has accrued its environmental and asset retirement obligations under the rule based on current estimates as of March 31, 2018 . East/West New Source Review — The EPA and various states have been investigating compliance of electric generating facilities with the pre-construction permitting requirements of the CAA known as “new source review,” or NSR. In 2007, Midwest Generation received an NOV from the EPA alleging that past work at Crawford, Fisk, Joliet, Powerton, Waukegan and Will County generating stations violated NSR and other regulations. These alleged violations are the subject of litigation described in Note 14 , Commitments and Contingencies . Additionally, in April 2013, the Connecticut Department of Energy and Environmental Protection issued four NOVs alleging that past work at oil-fired combustion turbines at the Torrington Terminal, Franklin, Branford and Middletown generating stations violated regulations regarding NSR.

Condensed Consolidating Financi

Condensed Consolidating Financial Information	3 Months Ended
	Mar. 31, 2018
Condensed Consolidating Financial Information Disclosure [Abstract]
Condensed Consolidating Financial Information	Condensed Consolidating Financial Information As of March 31, 2018 , the Company had outstanding $4.8 billion of Senior Notes due from 2022 to 2028, as shown in Note 7 , Debt and Capital Leases . These Senior Notes are guaranteed by certain of NRG's current and future 100% owned domestic subsidiaries, or guarantor subsidiaries. These guarantees are both joint and several. The non-guarantor subsidiaries include all of NRG's foreign subsidiaries and certain domestic subsidiaries, and NRG Yield, Inc. and its subsidiaries. Unless otherwise noted below, each of the following guarantor subsidiaries fully and unconditionally guaranteed the Senior Notes as of March 31, 2018 : Ace Energy, Inc. New Genco GP, LLC NRG Northeast Affiliate Services Inc. Allied Home Warranty GP LLC Norwalk Power LLC NRG Norwalk Harbor Operations Inc. Allied Warranty LLC NRG Advisory Services LLC NRG Operating Services, Inc. Arthur Kill Power LLC NRG Affiliate Services Inc. NRG Oswego Harbor Power Operations Inc. Astoria Gas Turbine Power LLC NRG Arthur Kill Operations Inc. NRG PacGen Inc. Bayou Cove Peaking Power, LLC NRG Astoria Gas Turbine Operations Inc. NRG Portable Power LLC BidURenergy, Inc. NRG Bayou Cove LLC NRG Power Marketing LLC Cabrillo Power I LLC NRG Business Services LLC NRG Reliability Solutions LLC Cabrillo Power II LLC NRG Cabrillo Power Operations Inc. NRG Renter's Protection LLC Carbon Management Solutions LLC NRG California Peaker Operations LLC NRG Retail LLC Cirro Group, Inc. NRG Cedar Bayou Development Company, LLC NRG Retail Northeast LLC Cirro Energy Services, Inc. NRG Connected Home LLC NRG Rockford Acquisition LLC Conemaugh Power LLC NRG Connecticut Affiliate Services Inc. NRG Saguaro Operations Inc. Connecticut Jet Power LLC NRG Construction LLC NRG Security LLC Cottonwood Development LLC NRG Curtailment Solutions, Inc NRG Services Corporation Cottonwood Energy Company LP NRG Development Company Inc. NRG SimplySmart Solutions LLC Cottonwood Generating Partners I LLC NRG Devon Operations Inc. NRG South Central Affiliate Services Inc. Cottonwood Generating Partners II LLC NRG Dispatch Services LLC NRG South Central Generating LLC Cottonwood Generating Partners III LLC NRG Distributed Energy Resources Holdings LLC NRG South Central Operations Inc. Cottonwood Technology Partners LP NRG Distributed Generation PR LLC NRG South Texas LP Devon Power LLC NRG Dunkirk Operations Inc. NRG Texas C&I Supply LLC Dunkirk Power LLC NRG El Segundo Operations Inc. NRG Texas Gregory LLC Eastern Sierra Energy Company LLC NRG Energy Efficiency-L LLC NRG Texas Holding Inc. El Segundo Power, LLC NRG Energy Labor Services LLC NRG Texas LLC El Segundo Power II LLC NRG ECOKAP Holdings LLC NRG Texas Power LLC Energy Alternatives Wholesale, LLC NRG Energy Services Group LLC NRG Warranty Services LLC Energy Choice Solutions LLC NRG Energy Services International Inc. NRG West Coast LLC Energy Plus Holdings LLC NRG Energy Services LLC NRG Western Affiliate Services Inc. Energy Plus Natural Gas LLC NRG Generation Holdings, Inc. O'Brien Cogeneration, Inc. II Energy Protection Insurance Company NRG Greenco LLC ONSITE Energy, Inc. Everything Energy LLC NRG Home & Business Solutions LLC Oswego Harbor Power LLC Forward Home Security, LLC NRG Home Services LLC Reliant Energy Northeast LLC GCP Funding Company, LLC NRG Home Solutions LLC Reliant Energy Power Supply, LLC Green Mountain Energy Company NRG Home Solutions Product LLC Reliant Energy Retail Holdings, LLC Gregory Partners, LLC NRG Homer City Services LLC Reliant Energy Retail Services, LLC Gregory Power Partners LLC NRG Huntley Operations Inc. RERH Holdings, LLC Huntley Power LLC NRG HQ DG LLC Saguaro Power LLC Independence Energy Alliance LLC NRG Identity Protect LLC Somerset Operations Inc. Independence Energy Group LLC NRG Ilion Limited Partnership Somerset Power LLC Independence Energy Natural Gas LLC NRG Ilion LP LLC Texas Genco GP, LLC Indian River Operations Inc. NRG International LLC Texas Genco Holdings, Inc. Indian River Power LLC NRG Maintenance Services LLC Texas Genco LP, LLC Keystone Power LLC NRG Mextrans Inc. Texas Genco Services, LP Louisiana Generating LLC NRG MidAtlantic Affiliate Services Inc. US Retailers LLC Meriden Gas Turbines LLC NRG Middletown Operations Inc. Vienna Operations Inc. Middletown Power LLC NRG Montville Operations Inc. Vienna Power LLC Montville Power LLC NRG New Roads Holdings LLC WCP (Generation) Holdings LLC NEO Corporation NRG North Central Operations Inc. West Coast Power LLC NRG conducts much of its business through and derives much of its income from its subsidiaries. Therefore, the Company's ability to make required payments with respect to its indebtedness and other obligations depends on the financial results and condition of its subsidiaries and NRG's ability to receive funds from its subsidiaries. There are no restrictions on the ability of any of the guarantor subsidiaries to transfer funds to NRG. However, there may be restrictions for certain non-guarantor subsidiaries. The following condensed consolidating financial information presents the financial information of NRG Energy, Inc., the guarantor subsidiaries and the non-guarantor subsidiaries in accordance with Rule 3-10 under the SEC Regulation S-X. The financial information may not necessarily be indicative of results of operations or financial position had the guarantor subsidiaries or non-guarantor subsidiaries operated as independent entities. In this presentation, NRG Energy, Inc. consists of parent company operations. Guarantor subsidiaries and non-guarantor subsidiaries of NRG are reported on an equity basis. For companies acquired, the fair values of the assets and liabilities acquired have been presented on a push-down accounting basis. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 1,483 $ 885 $ — $ 53 $ 2,421 Operating Costs and Expenses Cost of operations 1,082 409 14 53 1,558 Depreciation and amortization 73 154 8 — 235 Selling, general and administrative 98 32 61 — 191 Reorganization costs 2 — 18 — 20 Development costs — 9 4 — 13 Total operating costs and expenses 1,255 604 105 53 2,017 Gain/(loss) on sale of assets 3 (1 ) — — 2 Operating Income/(Loss) 231 280 (105 ) — 406 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 210 — 330 (540 ) — Equity in losses of unconsolidated affiliates — (1 ) (1 ) — (2 ) Other income/(expense), net 21 (11 ) 3 (16 ) (3 ) Loss on debt extinguishment, net — — (2 ) — (2 ) Interest expense (3 ) (72 ) (92 ) (167 ) Total other income/(expense) 228 (84 ) 238 (556 ) (174 ) Income Before Income Taxes 459 196 133 (556 ) 232 Income tax expense/(benefit) 113 48 (162 ) — (1 ) Net Income 346 148 295 (556 ) 233 Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests — (46 ) 16 (16 ) (46 ) Net Income Attributable to NRG Energy, Inc. $ 346 $ 194 $ 279 $ (540 ) $ 279 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME For the three months ended March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income $ 346 $ 148 $ 295 $ (556 ) $ 233 Other Comprehensive (Loss)/Income, net of tax Unrealized gain on derivatives, net — 16 15 (17 ) 14 Foreign currency translation adjustments, net (2 ) (2 ) (3 ) 5 (2 ) Defined benefit plans, net — — (1 ) — (1 ) Other comprehensive (loss)/income (2 ) 14 11 (12 ) 11 Comprehensive Income 344 162 306 (568 ) 244 Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (46 ) 24 (16 ) (38 ) Comprehensive Income Attributable to NRG Energy, Inc. $ 344 $ 208 $ 282 $ (552 ) $ 282 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated ASSETS (In millions) Current Assets Cash and cash equivalents $ 43 $ 371 $ 350 $ — $ 764 Funds deposited by counterparties 241 — — — 241 Restricted cash 8 399 — — 407 Accounts receivable, net 610 290 3 — 903 Inventory 323 205 — — 528 Derivative instruments 932 207 12 (136 ) 1,015 Cash collateral paid in support of energy risk management activities 211 — — — 211 Accounts receivable - affiliate 509 141 491 (1,068 ) 73 Current assets - held for sale — 89 — — 89 Prepayments and other current assets 154 134 38 — 326 Total current assets 3,031 1,836 894 (1,204 ) 4,557 Property, plant and equipment, net 2,500 11,196 240 (25 ) 13,911 Other Assets Investment in subsidiaries 511 1 7,374 (7,886 ) — Equity investments in affiliates — 1,010 1 — 1,011 Goodwill 360 179 — — 539 Intangible assets, net 439 1,290 — (3 ) 1,726 Nuclear decommissioning trust fund 680 — — — 680 Derivative instruments 245 118 38 (47 ) 354 Deferred income tax 264 (34 ) (94 ) — 136 Non-current assets held-for-sale — 157 — — 157 Other non-current assets 73 489 119 — 681 Total other assets 2,572 3,210 7,438 (7,936 ) 5,284 Total Assets $ 8,103 $ 16,242 $ 8,572 $ (9,165 ) $ 23,752 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 935 $ 21 $ — $ 956 Accounts payable 510 241 36 — 787 Accounts payable — affiliate 1,662 (121 ) (441 ) (1,068 ) 32 Derivative instruments 857 69 — (136 ) 790 Cash collateral received in support of energy risk management activities 240 — — — 240 Current liabilities held-for-sale — 80 — — 80 Accrued expenses and other current liabilities 236 146 280 — 662 Accrued expenses and other current liabilities-affiliate — — 161 — 161 Total current liabilities 3,505 1,350 57 (1,204 ) 3,708 Other Liabilities Long-term debt and capital leases 244 8,387 6,775 — 15,406 Nuclear decommissioning reserve 272 — — — 272 Nuclear decommissioning trust liability 400 — — — 400 Deferred income taxes 112 64 (156 ) — 20 Derivative instruments 224 87 — (47 ) 264 Out-of-market contracts, net 62 139 — — 201 Non-current liabilities held-for-sale — 7 — — 7 Other non-current liabilities 419 324 393 — 1,136 Total non-current liabilities 1,733 9,008 7,012 (47 ) 17,706 Total liabilities 5,238 10,358 7,069 (1,251 ) 21,414 Redeemable noncontrolling interest in subsidiaries — 80 — — 80 Stockholders’ Equity 2,865 5,804 1,503 (7,914 ) 2,258 Total Liabilities and Stockholders’ Equity $ 8,103 $ 16,242 $ 8,572 $ (9,165 ) $ 23,752 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the three months ended March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income $ 346 $ 148 $ 295 $ (556 ) $ 233 Adjustments to reconcile net income to net cash provided/(used) by operating activities: Distributions from unconsolidated affiliates — 13 — (3 ) 10 Equity in losses of unconsolidated affiliates — 1 1 — 2 Depreciation and amortization 73 154 8 — 235 Provision for bad debts 17 (2 ) — — 15 Amortization of nuclear fuel 13 — — — 13 Amortization of financing costs and debt discount/premiums — 10 4 — 14 Adjustment for debt extinguishment — — 2 — 2 Amortization of intangibles and out-of-market contracts 3 19 — — 22 Amortization of unearned equity compensation — — 13 — 13 Changes in deferred income taxes and liability for uncertain tax benefits 114 27 (144 ) — (3 ) Changes in nuclear decommissioning trust liability 34 — — — 34 Changes in derivative instruments 5 (220 ) (14 ) (18 ) (247 ) Changes in collateral deposits in support of energy risk management activities 162 1 — — 163 Gain on sale of emission allowances (8 ) — — — (8 ) (Gain)/loss on sale of assets (3 ) 1 — — (2 ) Changes in other working capital (442 ) 22 (296 ) 577 (139 ) Net Cash Provided/(Used) by Operating Activities 314 174 (131 ) — 357 Cash Flows from Investing Activities Dividends from NRG Yield, Inc. — — 25 (25 ) — Acquisition of Drop Down Assets, net of cash acquired — (42 ) — 42 — Acquisition of business, net of cash acquired (2 ) (60 ) — — (62 ) Capital expenditures (61 ) (276 ) (21 ) — (358 ) Decrease in notes receivable — 3 — — 3 Purchases of emission allowances (17 ) — — — (17 ) Proceeds from sale of emission allowances 23 — — — 23 Investments in nuclear decommissioning trust fund securities (216 ) — — — (216 ) Proceeds from the sale of nuclear decommissioning trust fund securities 182 — — — 182 Proceeds from sale of assets, net of cash disposed of 10 1 — — 11 Change in investments in unconsolidated affiliates — 2 — — 2 Net Cash (Used)/Provided by Investing Activities (81 ) (372 ) 4 17 (432 ) Cash Flows from Financing Activities Dividends from NRG Yield, Inc. — (25 ) — 25 — Payment from/(for) intercompany loans 18 80 (98 ) — — Acquisition of Drop Down Assets, net of cash acquired — — 42 (42 ) — Payment of dividends to common and preferred stockholders — — (10 ) — (10 ) Payment for treasury stock — — (93 ) — (93 ) Proceeds from issuance of long-term debt — 179 — — 179 Payments for short and long-term debt — (222 ) (6 ) — (228 ) Contributions from, net of distributions to noncontrolling interests in subsidiaries — 110 — — 110 Payment of debt issuance costs — (6 ) (1 ) — (7 ) Net Cash Provided/(Used) by Financing Activities 18 116 (166 ) (17 ) (49 ) Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash 251 (82 ) (293 ) — (124 ) Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 41 852 643 — 1,536 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 292 $ 770 $ 350 $ — $ 1,412 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended March 31, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 1,599 $ 867 $ — $ (84 ) $ 2,382 Operating Costs and Expenses Cost of operations 1,260 664 18 (80 ) 1,862 Depreciation and amortization 99 150 8 — 257 Selling, general and administrative 96 46 118 — 260 Development costs — 12 5 — 17 Total operating costs and expenses 1,455 872 149 (80 ) 2,396 Other income - affiliate — — 48 — 48 Gain on sale of assets 2 — — — 2 Operating Income/(Loss) 146 (5 ) (101 ) (4 ) 36 Other (Expense)/Income Equity in (losses)/earnings of consolidated subsidiaries (42 ) 1 68 (27 ) — Equity in (losses)/earnings of unconsolidated affiliates (1 ) 7 (1 ) — 5 Other (expense)/income, net (2 ) 5 7 3 13 Loss on debt extinguishment, net — (2 ) — — (2 ) Interest expense (4 ) (104 ) (117 ) — (225 ) Total other expense (49 ) (93 ) (43 ) (24 ) (209 ) Income/(Loss) from Continuing Operations Before Income Taxes 97 (98 ) (144 ) (28 ) (173 ) Income tax expense/(benefit) 19 (46 ) 25 (2 ) (4 ) Income/(Loss) from Continuing Operations 78 (52 ) (169 ) (26 ) (169 ) (Loss)/income from discontinued operations, net of income tax — (37 ) 3 — (34 ) Net Income/(Loss) 78 (89 ) (166 ) (26 ) (203 ) Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interest — (38 ) (3 ) 1 (40 ) Net Income/(Loss) Attributable to NRG Energy, Inc. $ 78 $ (51 ) $ (163 ) $ (27 ) $ (163 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) For the three months ended March 31, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income/(Loss) $ 78 $ (89 ) $ (166 ) $ (26 ) $ (203 ) Other Comprehensive Income, net of tax Unrealized gain on derivatives, net — 5 4 (5 ) 4 Foreign currency translation adjustments, net 5 4 7 (9 ) 7 Defined benefit plans, net — 1 (1 ) — — Other comprehensive income 5 10 10 (14 ) 11 Comprehensive Income/(Loss) 83 (79 ) (156 ) (40 ) (192 ) Less: Comprehensive loss attributable to noncontrolling interest and redeemable noncontrolling interest — (37 ) (3 ) 1 (39 ) Comprehensive Income/(Loss) Attributable to NRG Energy, Inc. $ 83 $ (42 ) $ (153 ) $ (41 ) $ (153 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS December 31, 2017 Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated ASSETS (In millions) Current Assets Cash and cash equivalents $ — $ 348 $ 643 $ — $ 991 Funds deposited by counterparties 37 — — — 37 Restricted cash 4 504 — — 508 Accounts receivable, net 768 307 4 — 1,079 Inventory 338 194 — — 532 Derivative instruments 625 81 9 (89 ) 626 Cash collateral paid in support of energy risk management activities 170 1 — — 171 Accounts receivable - affiliate 709 213 (129 ) (698 ) 95 Current assets held-for-sale 8 107 — — 115 Prepayments and other current assets 116 118 27 — 261 Total current assets 2,775 1,873 554 (787 ) 4,415 Property, plant and equipment, net 2,502 11,194 238 (26 ) 13,908 Other Assets Investment in subsidiaries 305 — 7,581 (7,886 ) — Equity investments in affiliates — 1,036 2 — 1,038 Goodwill 360 179 — — 539 Intangible assets, net 454 1,295 — (3 ) 1,746 Nuclear decommissioning trust fund 692 — — — 692 Derivative instruments 121 40 31 (20 ) 172 Deferred income taxes 377 (7 ) (236 ) — 134 Non-current assets held for sale — 43 — — 43 Other non-current assets 50 461 158 (38 ) 631 Total other assets 2,359 3,047 7,536 (7,947 ) 4,995 Total Assets $ 7,636 $ 16,114 $ 8,328 $ (8,760 ) $ 23,318 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 667 $ 59 $ (38 ) $ 688 Accounts payable 545 281 55 — 881 Accounts payable — affiliate 751 (201 ) 181 (698 ) 33 Derivative instruments 535 108 — (88 ) 555 Cash collateral received in support of energy risk management activities 37 — — — 37 Current liabilities held-for-sale — 72 — — 72 Accrued expenses and other current liabilities 290 175 425 — 890 Accrued expenses and other current liabilities - affiliate — — 161 — 161 Total current liabilities 2,158 1,102 881 (824 ) 3,317 Other Liabilities Long-term debt and capital leases 244 8,733 6,739 — 15,716 Nuclear decommissioning reserve 269 — — — 269 Nuclear decommissioning trust liability 415 — — — 415 Deferred income taxes 112 64 (155 ) — 21 Derivative instruments 110 107 — (20 ) 197 Out-of-market contracts, net 66 141 — — 207 Non-current liabilities held-for-sale — 8 — — 8 Other non-current liabilities 410 321 391 — 1,122 Total non-current liabilities 1,626 9,374 6,975 (20 ) 17,955 Total Liabilities 3,784 10,476 7,856 (844 ) 21,272 Redeemable noncontrolling interest in subsidiaries — 78 — — 78 Stockholders’ Equity 3,852 5,560 472 (7,916 ) 1,968 Total Liabilities and Stockholders’ Equity $ 7,636 $ 16,114 $ 8,328 $ (8,760 ) $ 23,318 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the three months ended March 31, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income/(loss) $ 78 $ (89 ) $ (166 ) $ (26 ) $ (203 ) (Loss)/income from discontinued operations — (37 ) 3 — (34 ) Net income/(loss) from continuing operations 78 (52 ) (169 ) (26 ) (169 ) Adjustments to reconcile net income/(loss) to net cash (used)/provided by operating activities: Distributions from unconsolidated affiliates — 18 — (5 ) 13 Equity in losses/(earnings) of unconsolidated affiliates 1 (7 ) 1 — (5 ) Depreciation and amortization 99 150 8 — 257 Provision for bad debts 8 1 — — 9 Amortization of nuclear fuel 12 — — — 12 Amortization of financing costs and debt discount/premiums — 11 4 — 15 Amortization of intangibles and out-of-market contracts 6 24 — — 30 Amortization of unearned equity compensation — — 8 — 8 Changes in deferred income taxes and liability for uncertain tax benefits 19 (46 ) 28 — 1 Changes in nuclear decommissioning trust liability 36 — — — 36 Changes in derivative instruments (4 ) 43 (1 ) — 38 Changes in collateral deposits in support of energy risk management activities (136 ) 9 — — (127 ) Gain on sale of assets (2 ) — — — (2 ) Changes in other working capital (118 ) 458 (601 ) 63 (198 ) Net cash (used)/provided by continuing operations (1 ) 609 (722 ) 32 (82 ) Cash provided by discontinued operations — 15 — — 15 Net Cash (Used)/Provided by Operating Activities (1 ) 624 (722 ) 32 (67 ) Cash Flows from Investing Activities Dividends from NRG Yield, Inc. — — 22 (22 ) — Intercompany dividends — — 129 (129 ) — Acquisition of Drop Down Assets, net of cash acquired — (131 ) — 131 — Acquisition of businesses, net of cash acquired — (3 ) — — (3 ) Capital expenditures (64 ) (168 ) (4 ) — (236 ) Decrease in notes receivable — 4 — — 4 Purchases of emission allowances (9 ) — — — (9 ) Proceeds from sale of emission allowances 11 — — — 11 Investments in nuclear decommissioning trust fund securities (153 ) — — — (153 ) Proceeds from the sale of nuclear decommissioning trust fund securities 117 — — — 117 Proceeds from sale of assets, net of cash disposed of 11 3 — — 14 Change in investments in unconsolidated affiliates — (12 ) — — (12 ) Other 18 — — — 18 Net cash (used)/provided by continuing operations (69 ) (307 ) 147 (20 ) (249 ) Cash used by discontinued operations — (32 ) — — (32 ) Net Cash (Used)/Provided by Investing Activities (69 ) (339 ) 147 (20 ) (281 ) Cash Flows from Financing Activities Dividends from NRG Yield, Inc. — (22 ) — 22 — Payments (for)/from intercompany loans 65 (428 ) 395 (32 ) — Acquisition of Drop Down Assets, net of cash acquired — — 131 (131 ) — Intercompany dividends — (129 ) — 129 — Payment of dividends to common and preferred stockholders — — (9 ) — (9 ) Net receipts from settlement of acquired derivatives that include financing elements — 1 — — 1 Proceeds from issuance of long-term debt — 167 26 — 193 Payments for short and long-term debt — (146 ) (31 ) — (177 ) Distributions to, net of contributions from, noncontrolling interests in subsidiaries — (5 ) — — (5 ) Payment of debt issuance costs — (10 ) (4 ) — (14 ) Other - contingent consideration — (10 ) — — (10 ) Net cash provided/(used) by continuing operations 65 (582 ) 508 (12 ) (21 ) Cash used by discontinued operations — (132 ) — — (132 ) Net Cash Provided/(Used) by Financing Activities 65 (714 ) 508 (12 ) (153 ) Effect of exchange rate changes on cash and cash equivalents — (7 ) — — (7 ) Change in cash from discontinued operations — (149 ) — — (149 ) Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash (5 ) (287 ) (67 ) — (359 ) Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 13 1,050 323 — 1,386 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 8 $ 763 $ 256 $ — $ 1,027 (a) All significant intercompany transactions have been eliminated in consolidation.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified for comparative purposes. The reclassifications did not affect results from operations, net assets or cash flows.
Revenue Recognition	Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606 using the modified retrospective method applied to contracts which were not completed as of the adoption date. The Company recognized the cumulative effect of initially applying the new standard as a credit to the opening balance of accumulated deficit, resulting in a decrease of approximately $16 million . The adjustment primarily related to costs incurred to obtain a contract with customers and customer incentives. 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. Retail Revenues Gross revenues for energy sales and services to retail customers are recognized as the Company transfers the promised goods and services to the customer. For the majority of its electricity contracts, the Company’s performance obligation with the customer is satisfied over time and performance obligations for its electricity products are recognized as the customer takes possession of the product. The Company also allocates the contract consideration to distinct performance obligation in a contract for which the timing of the revenue recognized is different. Additionally, customer discounts and incentives reduce the contract consideration and are recognized over the term of the contract. Energy sales and services that have been delivered but not billed by period end are estimated. Accrued unbilled revenues are based on estimates of customer usage since the date of the last meter reading provided by the independent system operators or electric distribution companies. Volume estimates are based on daily forecasted volumes and estimated customer usage by class. Unbilled revenues are calculated by multiplying these volume estimates by the applicable rate by customer class. Estimated amounts are adjusted when actual usage is known and billed. As contracts for retail electricity can be for multi-year periods, 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 amount of any unsatisfied performance obligations will vary based on customer usage, which will depend on factors such as weather and customer activity and therefore it is not practicable to estimate such amounts. Energy Revenue Both physical and financial transactions are entered into to optimize the financial performance of the Company's generating facilities. Electric energy revenue is recognized upon transmission to the customer over time, using the output method for measuring progress of satisfaction of performance obligations. Physical transactions, or the sale of generated electricity to meet supply and demand, are recorded on a gross basis in the Company's consolidated statements of operations. The Company applies the invoicing practical expedient, where applicable, in recognizing energy revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Financial transactions, or the buying and selling of energy for trading purposes, are recorded net within operating revenues in the consolidated statements of operations in accordance with ASC 815. Capacity Revenue Capacity revenues consist of revenues billed to a third party at either the market or a negotiated contract price for making installed generation capacity available in order to satisfy system integrity and reliability requirements. Capacity revenues are recognized over time, using the output method for measuring progress of satisfaction of performance obligations. The Company applies the invoicing practical expedient, where applicable, in recognizing capacity revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Capacity revenue contracts mainly consist of: Capacity auctions — The Company's largest sources of capacity revenues are capacity auctions in PJM, ISO-NE, and NYISO. Both ISO-NE and PJM operate a pay-for-performance model where capacity payments are modified based on real-time performance, where NRG's actual revenues will be the combination of revenues based on the cleared auction MWs plus the net of any over- and under-performance of NRG's fleet. In addition, MISO has an annual auction, known as the Planning Resource Auction, or PRA. The Gulf Coast assets situated in the MISO market may participate in this auction. Estimated revenues for cleared auction MWs in the various capacity auctions are $554 million , $508 million , $423 million , $222 million and $57 million for fiscal years 2018 , 2019 , 2020 , 2021 and 2022 , respectively. Resource adequacy and bilateral contracts — In California, there is a resource adequacy requirement that is primarily satisfied through bilateral contracts. Such bilateral contracts are typically short-term resource adequacy contracts. When bilateral contracting does not satisfy the resource adequacy need, such shortfalls can be addressed through procurement tools administered by the CAISO, including the capacity procurement mechanism or reliability must-run contracts. Demand payments from the current long-term contracts are tied to summer peak demand and provide a mechanism for recovering a portion of the costs associated with new or changed environmental laws or regulations. In Texas, capacity and contracted revenues are through bilateral contracts with load serving entities. Long-term PPAs — Energy, capacity and where applicable, renewable attributes, from the majority of 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. Many of these PPAs are accounted for as leases. Renewable Energy Credits As stated above, renewable energy credits 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 inventory 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 table represents the Company’s disaggregation of revenue from contracts with customers for the three months ended March 31, 2018 , along with the reportable segment for each category: Three months ended March 31, 2018 Generation (In millions) Retail Gulf Coast East/West (a) Subtotal Renewables NRG Yield Eliminations Total Energy revenue (a)(b) $ — $ 371 $ 218 $ 589 $ 77 $ 114 $ (161 ) $ 619 Capacity revenue (a)(b) — 67 140 207 — 82 (1 ) 288 Retail revenue Mass customers 1,171 — — — — — (1 ) 1,170 Business solutions customers 316 — — — — — — 316 Total retail revenue 1,487 — — — — — (1 ) 1,486 Mark-to-market for economic hedging activities (c) (6 ) (564 ) (10 ) (574 ) (10 ) — 484 (106 ) Contract amortization — 3 — 3 — (17 ) — (14 ) Other revenue (a)(b) — 86 16 102 19 46 (19 ) 148 Total operating revenue 1,481 (37 ) 364 327 86 225 302 2,421 Less: Lease revenue 6 — 1 1 64 181 — 252 Less: Derivative revenue (6 ) (188 ) 80 (108 ) (10 ) — 484 360 Less: Contract amortization — 3 — 3 — (17 ) — (14 ) Total revenue from contracts with customers $ 1,481 $ 148 $ 283 $ 431 $ 32 $ 61 $ (182 ) $ 1,823 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Retail Gulf Coast East/West Subtotal Renewables NRG Yield Eliminations Total Energy revenue — — — — 61 102 — 163 Capacity revenue — — — — — 79 — 79 Other revenue 6 — 1 1 3 — — 10 (b) The following amounts of energy and capacity revenue relate to derivative instruments and are accounted for under ASC 815. Retail Gulf Coast East/West Subtotal Renewables NRG Yield Eliminations Total Energy revenue — 371 61 432 — — — 432 Capacity revenue — — 26 26 — — — 26 Other revenue — 5 3 8 — — — 8 (c) Revenue relates entirely to unrealized gains and losses on derivative instruments accounted for under ASC 815. Contract Amortization Assets and liabilities recognized from power sales agreements assumed at Fresh Start and 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. Lease Revenue Certain of the Company’s revenues are obtained through PPAs or other contractual agreements. Many of these agreements are accounted for as operating leases under ASC 840 Leases. Certain of these leases have no minimum lease payments and all of the rent is recorded as contingent rent on an actual basis when the electricity is delivered. 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.
Revenue Recognition, Customer Acquisitions	The Company’s customer acquisition costs consist of broker fees, commission payments and other costs that represent incremental costs of obtaining the contract with customers for which the Company expects to recover. The Company amortizes these amounts over the estimated life of the customer contract. As a practical expedient, the Company expenses the incremental costs of obtaining a contract if the amortization period of the asset would have been one year or less.
Revenue Recognition, Deferred Revenue	When the Company receives consideration from the customer that is in excess of the amount due, such consideration is reclassified to deferred revenue, which represents a contract liability. Generally, the Company will recognize revenue from contract liabilities in the next period as the Company satisfies its performance obligations.
Recent Accounting Developments	Recent Accounting Developments - Guidance Adopted in 2018 ASU 2017-07 — In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715) , Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, or ASU No. 2017-07. Current GAAP does not indicate where the amount of net benefit cost should be presented in an entity’s income statement and does not require entities to disclose the amount of net benefit cost that is included in the income statement. The amendments of ASU No. 2017-07 require an entity to report the service cost component of net benefit costs in the same line item as other compensation costs arising from services rendered by the related employees during the applicable service period. The other components of net benefit cost are required to be presented separately from the service cost component and outside the subtotal of income from operations. Further, ASU No. 2017-07 prescribes that only the service cost component of net benefit costs is eligible for capitalization. The Company adopted the amendments of ASU No. 2017-07 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance retrospectively which resulted in an increase in cost of operations of $4 million and a corresponding increase in other income, net on the statement of operations for the three months ended March 31, 2017 . ASU 2016-01 - In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , or ASU No. 2016-01. The amendments of ASU No. 2016-01 eliminate available-for-sale classification of equity investments and require that equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) be generally measured at fair value with changes in fair value recognized in net income. Further, the amendments require that financial assets and financial liabilities be presented separately in the notes to the financial statements, grouped by measurement category and form of financial asset. The guidance in ASU No. 2016-01 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those annual periods. The Company adopted the amendments of ASU No. 2016-01 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance on a modified retrospective basis, which resulted in no material adjustments recorded to the consolidated results of operations, cash flows, and statement of financial position. Recent Accounting Developments - Guidance 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 which includes the evaluation of lease contracts compared to the new standard. 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, NRG believes the adoption of Topic 842 will have a material impact on its financial statements. The Company is also monitoring recent changes to Topic 842 and the related impact on the implementation process.
Nuclear Decommissioning	NRG's Nuclear Decommissioning Trust Fund assets are comprised of securities classified as available-for-sale and recorded at fair value based on actively quoted market prices. NRG accounts for the Nuclear Decommissioning Trust Fund in accordance with ASC 980, Regulated Operations , because the Company's nuclear decommissioning activities are subject to approval by the PUCT with regulated rates that are designed to recover all decommissioning costs and that can be charged to and collected from the ratepayers per PUCT mandate. Since the Company is in compliance with PUCT rules and regulations regarding decommissioning trusts and the cost of decommissioning is the responsibility of the Texas ratepayers, not NRG, all realized and unrealized gains or losses (including other-than-temporary impairments) related to the Nuclear Decommissioning Trust Fund are recorded to the Nuclear Decommissioning Trust liability and are not included in net income or accumulated OCI, consistent with regulatory treatment.
Segment Reporting	The Company's segment structure reflects how management currently makes financial decisions and allocates resources. The Company's businesses are segregated as follows: Generation, which includes generation, international and BETM; Retail, which includes Mass customers and Business Solutions, which includes C&I customers and other distributed and reliability products; Renewables, which includes solar and wind assets, excluding those in NRG Yield; NRG Yield; and corporate activities. During 2017, NRG Yield acquired several projects totaling 555 MW from NRG. On March 30, 2018, the Company sold to NRG Yield, Inc. 100% of NRG's interests in Buckthorn Renewables, LLC, which owns a 154 MW construction-stage utility-scale solar generation project, located in Texas. These acquisitions were treated as a transfer of entities under common control and accordingly, all historical periods have been recast to reflect the acquisition as if they had occurred at the beginning of the financial statement period. On June 14, 2017, as described in Note 3 , Discontinued Operations and Dispositions , NRG deconsolidated GenOn for financial reporting purposes. The financial information for all historical periods have been recast to reflect the presentation of GenOn as discontinued operations within the corporate segment. NRG’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, free cash flow and capital for allocation, as well as net income/(loss).

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Other Balance Sheet Information	The following table presents the allowance for doubtful accounts included in accounts receivable, net; accumulated depreciation included in property, plant and equipment, net; accumulated amortization included in intangible assets, net and accumulated amortization included in out-of-market contracts, net: March 31, 2018 December 31, 2017 (In millions) Accounts receivable allowance for doubtful accounts $ 27 $ 28 Property, plant and equipment accumulated depreciation 4,679 4,465 Intangible assets accumulated amortization 1,393 1,818 Out-of-market contracts accumulated amortization 364 358
Reconciliation of Cash and Cash Equivalents, Restricted Cash and Funds Deposited by Counterparties	The following table provides a reconciliation of cash and cash equivalents, restricted cash and funds deposited by counterparties reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the statement of cash flows. March 31, 2018 December 31, 2017 March 31, 2017 December 31, 2016 (In millions) Cash and cash equivalents $ 764 $ 991 $ 627 $ 938 Funds deposited by counterparties 241 37 3 2 Restricted cash 407 508 397 446 Cash and cash equivalents, funds deposited by counterparties and restricted cash shown in the statement of cash flows $ 1,412 $ 1,536 $ 1,027 $ 1,386
Schedule of Change in Noncontrolling Interest	Noncontrolling Interest The following table reflects the changes in NRG's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 2,314 Dividends paid to NRG Yield, Inc. public shareholders (30 ) Distributions to noncontrolling interest (19 ) Comprehensive loss attributable to noncontrolling interest (22 ) Non-cash adjustments to noncontrolling interest 6 Contributions from noncontrolling interest 147 Sale of assets to NRG Yield, Inc. (4 ) Balance as of March 31, 2018 $ 2,392
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest The following table reflects the changes in the Company's redeemable noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 78 Distributions to redeemable noncontrolling interest (1 ) Contributions from redeemable noncontrolling interest 12 Non-cash adjustments to redeemable noncontrolling interest 7 Comprehensive loss attributable to redeemable noncontrolling interest (16 ) Balance as of March 31, 2018 $ 80
Disaggregation of Revenue from Contracts	The following table represents the Company’s disaggregation of revenue from contracts with customers for the three months ended March 31, 2018 , along with the reportable segment for each category: Three months ended March 31, 2018 Generation (In millions) Retail Gulf Coast East/West (a) Subtotal Renewables NRG Yield Eliminations Total Energy revenue (a)(b) $ — $ 371 $ 218 $ 589 $ 77 $ 114 $ (161 ) $ 619 Capacity revenue (a)(b) — 67 140 207 — 82 (1 ) 288 Retail revenue Mass customers 1,171 — — — — — (1 ) 1,170 Business solutions customers 316 — — — — — — 316 Total retail revenue 1,487 — — — — — (1 ) 1,486 Mark-to-market for economic hedging activities (c) (6 ) (564 ) (10 ) (574 ) (10 ) — 484 (106 ) Contract amortization — 3 — 3 — (17 ) — (14 ) Other revenue (a)(b) — 86 16 102 19 46 (19 ) 148 Total operating revenue 1,481 (37 ) 364 327 86 225 302 2,421 Less: Lease revenue 6 — 1 1 64 181 — 252 Less: Derivative revenue (6 ) (188 ) 80 (108 ) (10 ) — 484 360 Less: Contract amortization — 3 — 3 — (17 ) — (14 ) Total revenue from contracts with customers $ 1,481 $ 148 $ 283 $ 431 $ 32 $ 61 $ (182 ) $ 1,823 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Retail Gulf Coast East/West Subtotal Renewables NRG Yield Eliminations Total Energy revenue — — — — 61 102 — 163 Capacity revenue — — — — — 79 — 79 Other revenue 6 — 1 1 3 — — 10 (b) The following amounts of energy and capacity revenue relate to derivative instruments and are accounted for under ASC 815. Retail Gulf Coast East/West Subtotal Renewables NRG Yield Eliminations Total Energy revenue — 371 61 432 — — — 432 Capacity revenue — — 26 26 — — — 26 Other revenue — 5 3 8 — — — 8 (c) Revenue relates entirely to unrealized gains and losses on derivative instruments accounted for under ASC 815.
Contract with Customer, Asset and Liability	The following table reflects the contract assets and liabilities included in the Company’s balance sheet as of March 31, 2018 : (In millions) March 31, 2018 Deferred customer acquisition costs $ 85 Accounts receivable, net - Contracts with customers 784 Accounts receivable, net - Leases 81 Accounts receivable, net - Derivative instruments 38 Total accounts receivable, net 903 Unbilled revenues (included within Accounts receivable, net - Contracts with customers) 292 Deferred revenues 63

Discontinued Operations and D27

Discontinued Operations and Dispositions (Tables)	3 Months Ended
	Mar. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Summary of results of discontinued operations and major classes of assets and liabilities	Summarized results of discontinued operations were as follows: Three months ended March 31, 2017 (In millions) Operating revenues $ 381 Operating costs and expenses (373 ) Other expenses (44 ) Loss from operations of discontinued components, before tax (36 ) Income tax expense 1 Loss from operations of discontinued components (37 ) Interest income - affiliate 3 Loss from discontinued operations, net of tax $ (34 )

Fair Value of Financial Instr28

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Estimated carrying amounts and fair values of NRG's recorded financial instruments not carried at fair market value	The following table presents the level within the fair value hierarchy for long-term debt, including current portion as of March 31, 2018 and December 31, 2017 : As of March 31, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 8,772 $ 7,915 $ 8,934 $ 7,960 The estimated carrying amounts and fair values of NRG's recorded financial instruments not carried at fair market value are as follows: As of March 31, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable (a) $ 15 $ 14 $ 16 $ 15 Liabilities: Long-term debt, including current portion (b) 16,559 16,687 16,603 16,894 (a) Includes the current portion of notes receivable which is recorded in prepayments and other current assets on the Company's consolidated balance sheets. (b) Excludes deferred financing costs, which are recorded as a reduction to long-term debt on the Company's consolidated balance sheets.
Assets and liabilities measured and recorded at fair value on the consolidated balance sheets on a recurring basis	The following tables present assets and liabilities measured and recorded at fair value on the Company's condensed consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of March 31, 2018 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 22 $ 3 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 16 16 — — U.S. government and federal agency obligations 56 55 1 — Federal agency mortgage-backed securities 92 — 92 — Commercial mortgage-backed securities 16 — 16 — Corporate debt securities 100 — 100 — Equity securities 333 333 — — Foreign government fixed income securities 5 — 5 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 1,277 168 1,060 49 Interest rate contracts 92 — 92 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 62 Total assets $ 2,072 $ 576 $ 1,366 $ 68 Derivative liabilities: Commodity contracts 1,024 224 729 71 Interest rate contracts 30 — 30 — Total liabilities $ 1,054 $ 224 $ 759 $ 71 As of December 31, 2017 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 22 $ 3 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 47 45 2 — U.S. government and federal agency obligations 43 42 1 — Federal agency mortgage-backed securities 82 — 82 — Commercial mortgage-backed securities 14 — 14 — Corporate debt securities 99 — 99 — Equity securities 334 334 — — Foreign government fixed income securities 5 — 5 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 745 191 509 45 Interest rate contracts 53 — 53 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 68 Total assets $ 1,513 $ 616 $ 765 $ 64 Derivative liabilities: Commodity contracts 693 257 359 77 Interest rate contracts 59 — 59 — Total liabilities $ 752 $ 257 $ 418 $ 77
Reconciliation of beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements at least annually using significant unobservable inputs	The following tables reconcile, for the three months ended March 31, 2018 and 2017 , the beginning and ending balances for financial instruments that are recognized at fair value in the condensed consolidated financial statements, at least annually, using significant unobservable inputs: Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended March 31, 2018 (In millions) Debt Securities Derivatives (a) Total Beginning balance $ 19 $ (32 ) $ (13 ) Total gains — realized/unrealized: Included in earnings — 2 2 Purchases — 1 1 Transfers into Level 3 (b) — 4 4 Transfers out of Level 3 (b) — 3 3 Ending balance as of March 31, 2018 $ 19 $ (22 ) $ (3 ) Gains for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of March 31, 2018 $ — $ 3 $ 3 (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2. Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended March 31, 2017 (In millions) Debt Securities Trust Fund Investments Derivatives (a) Total Beginning balance $ 17 $ 54 $ (68 ) $ 3 Total gains — realized/unrealized: Included in earnings 1 — 6 7 Included in nuclear decommissioning obligation — 4 — 4 Purchases — — 4 4 Transfers into Level 3 (b) — — (8 ) (8 ) Transfers out of Level 3 (b) — — 10 10 Ending balance as of March 31, 2017 $ 18 $ 58 $ (56 ) $ 20 Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of March 31, 2017 $ — $ — $ (15 ) $ (15 ) (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2.
Significant unobservable inputs used developing fair valueets, Quantitative Information	The following tables quantify the significant unobservable inputs used in developing the fair value of the Company's Level 3 positions as of March 31, 2018 and December 31, 2017 : Significant Unobservable Inputs March 31, 2018 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 38 $ 63 Discounted Cash Flow Forward Market Price (per MWh) $ 9 $ 319 $ 40 FTRs 11 8 Discounted Cash Flow Auction Prices (per MWh) (28 ) 46 — $ 49 $ 71 Significant Unobservable Inputs December 31, 2017 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 34 $ 65 Discounted Cash Flow Forward Market Price (per MWh) $ 10 $ 142 $ 33 FTRs 11 12 Discounted Cash Flow Auction Prices (per MWh) (28 ) 46 — $ 45 $ 77
Fair value inputs, sensitivity analysis	The following table provides sensitivity of fair value measurements to increases/(decreases) in significant unobservable inputs as of March 31, 2018 and December 31, 2017 : Significant Unobservable Input Position Change In Input Impact on Fair Value Measurement Forward Market Price Power Buy Increase/(Decrease) Higher/(Lower) Forward Market Price Power Sell Increase/(Decrease) Lower/(Higher) FTR Prices Buy Increase/(Decrease) Higher/(Lower) FTR Prices Sell Increase/(Decrease) Lower/(Higher)
Net counterparty credit exposure by industry sector and by counterparty credit quality	The following tables highlight net counterparty credit exposure by industry sector and by counterparty credit quality. Net counterparty credit exposure is defined as the aggregate net asset position for NRG with counterparties where netting is permitted under the enabling agreement and includes all cash flow, mark-to-market and NPNS, and non-derivative transactions. The exposure is shown net of collateral held, and includes amounts net of receivables or payables. Net Exposure (a) (b) Category by Industry Sector (% of Total) Utilities, energy merchants, marketers and other 78 % Financial institutions 22 Total as of March 31, 2018 100 % Net Exposure (a) (b) Category by Counterparty Credit Quality (% of Total) Investment grade 78 % Non-Investment grade/Non-Rated 22 Total as of March 31, 2018 100 % (a) Counterparty credit exposure excludes uranium and coal transportation contracts because of the unavailability of market prices. (b) The figures in the tables above exclude potential counterparty credit exposure related to RTOs, ISOs, registered commodity exchanges and certain long term contracts.

Nuclear Decommissioning Trust29

Nuclear Decommissioning Trust Fund (Tables)	3 Months Ended
	Mar. 31, 2018
Nuclear Decommissioning Trust Fund Disclosure [Abstract]
Summary of aggregate fair values and unrealized gains and losses (including other-than-temporary impairments) for the securities held in the nuclear decommissioning trust fund	The following table summarizes the aggregate fair values and unrealized gains and losses (including other-than-temporary impairments) for the securities held in the trust funds, as well as information about the contractual maturities of those securities. As of March 31, 2018 As of December 31, 2017 (In millions, except otherwise noted) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Cash and cash equivalents $ 16 $ — $ — — $ 47 $ — $ — — U.S. government and federal agency obligations 56 1 1 11 43 1 — 11 Federal agency mortgage-backed securities 92 — 2 23 82 1 1 23 Commercial mortgage-backed securities 16 — 1 22 14 — — 20 Corporate debt securities 100 1 2 11 99 2 1 11 Equity securities 395 265 — — 402 272 — — Foreign government fixed income securities 5 — — 8 5 — — 9 Total $ 680 $ 267 $ 6 $ 692 $ 276 $ 2
Summary of proceeds from sales of available-for-sale securities and the related realized gains and losses	The following table summarizes proceeds from sales of available-for-sale securities and the related realized gains and losses from these sales. The cost of securities sold is determined on the specific identification method. Three months ended March 31, 2018 2017 (In millions) Realized gains $ 3 $ 2 Realized losses 3 2 Proceeds from sale of securities 182 117

Accounting for Derivative Ins30

Accounting for Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net notional volume buy/(sell) of NRG's open derivative transactions broken out by commodity	The following table summarizes the net notional volume buy/(sell) of NRG's open derivative transactions broken out by category, excluding those derivatives that qualified for the NPNS exception, as of March 31, 2018 and December 31, 2017 . Option contracts are reflected using delta volume. Delta volume equals the notional volume of an option adjusted for the probability that the option will be in-the-money at its expiration date. Total Volume March 31, 2018 December 31, 2017 Category Units (In millions) Emissions Short Ton 2 1 Coal Short Ton 17 21 Natural Gas MMBtu (208 ) (17 ) Power MWh 16 14 Capacity MW/Day (1 ) (1 ) Interest Dollars $ 3,938 $ 3,876 Equity Shares 1 1
Fair value within the derivative instrument valuation on the balance sheets	The following table summarizes the fair value within the derivative instrument valuation on the balance sheets: Fair Value Derivative Assets Derivative Liabilities March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 (In millions) Derivatives Designated as Cash Flow or Fair Value Hedges: Interest rate contracts current $ 2 $ 1 $ 2 $ 5 Interest rate contracts long-term 20 11 7 11 Total Derivatives Designated as Cash Flow or Fair Value Hedges 22 12 9 16 Derivatives Not Designated as Cash Flow or Fair Value Hedges: Interest rate contracts current 13 9 7 15 Interest rate contracts long-term 57 32 14 28 Commodity contracts current 1,000 616 781 535 Commodity contracts long-term 277 129 243 158 Total Derivatives Not Designated as Cash Flow or Fair Value Hedges 1,347 786 1,045 736 Total Derivatives $ 1,369 $ 798 $ 1,054 $ 752
Offsetting of derivatives by counterparty assets	The following table summarizes the offsetting of derivatives by counterparty master agreement level and collateral received or paid: Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of March 31, 2018 (In millions) Commodity contracts: Derivative assets $ 1,277 $ (835 ) $ (201 ) $ 241 Derivative liabilities (1,024 ) 835 120 (69 ) Total commodity contracts 253 — (81 ) 172 Interest rate contracts: Derivative assets 92 (4 ) — 88 Derivative liabilities (30 ) 4 — (26 ) Total interest rate contracts 62 — — 62 Total derivative instruments $ 315 $ — $ (81 ) $ 234 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of December 31, 2017 (In millions) Commodity contracts: Derivative assets $ 745 $ (578 ) $ (11 ) $ 156 Derivative liabilities (693 ) 578 73 (42 ) Total commodity contracts 52 — 62 114 Interest rate contracts: Derivative assets 53 (3 ) — 50 Derivative liabilities (59 ) 3 — (56 ) Total interest rate contracts (6 ) — — (6 ) Total derivative instruments $ 46 $ — $ 62 $ 108
Offsetting of derivatives by counterparty, liabilities	The following table summarizes the offsetting of derivatives by counterparty master agreement level and collateral received or paid: Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of March 31, 2018 (In millions) Commodity contracts: Derivative assets $ 1,277 $ (835 ) $ (201 ) $ 241 Derivative liabilities (1,024 ) 835 120 (69 ) Total commodity contracts 253 — (81 ) 172 Interest rate contracts: Derivative assets 92 (4 ) — 88 Derivative liabilities (30 ) 4 — (26 ) Total interest rate contracts 62 — — 62 Total derivative instruments $ 315 $ — $ (81 ) $ 234 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of December 31, 2017 (In millions) Commodity contracts: Derivative assets $ 745 $ (578 ) $ (11 ) $ 156 Derivative liabilities (693 ) 578 73 (42 ) Total commodity contracts 52 — 62 114 Interest rate contracts: Derivative assets 53 (3 ) — 50 Derivative liabilities (59 ) 3 — (56 ) Total interest rate contracts (6 ) — — (6 ) Total derivative instruments $ 46 $ — $ 62 $ 108
Effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax	The following table summarizes the effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax: Interest Rate Contracts Three months ended March 31, 2018 2017 (In millions) Accumulated OCI beginning balance $ (54 ) $ (66 ) Reclassified from accumulated OCI to income: Due to realization of previously deferred amounts 4 3 Mark-to-market of cash flow hedge accounting contracts 19 2 Accumulated OCI ending balance, net of $6, and $14 tax $ (31 ) $ (61 ) Losses expected to be realized from OCI during the next 12 months, net of $2 tax $ (9 )
Pre-tax effects of economic hedges that have not been designated as cash flow hedges, ineffectiveness on cash flow hedges and trading activity on the Company's statement of operations	The following table summarizes the pre-tax effects of economic hedges that have not been designated as cash flow hedges and trading activity on the Company's statement of operations. The effect of energy commodity contracts is included within operating revenues and cost of operations and the effect of interest rate contracts is included in interest expense. Three months ended March 31, 2018 2017 Unrealized mark-to-market results (In millions) Reversal of previously recognized unrealized losses on settled positions related to economic hedges $ 2 $ 3 Net unrealized gains/(losses) on open positions related to economic hedges 194 (22 ) Total unrealized mark-to-market gains/(losses) for economic hedging activities 196 (19 ) Reversal of previously recognized unrealized gains on settled positions related to trading activity (3 ) (15 ) Net unrealized gains on open positions related to trading activity 11 1 Total unrealized mark-to-market gains/(losses) for trading activity 8 (14 ) Total unrealized gains/(losses) $ 204 $ (33 ) Three months ended March 31, 2018 2017 (In millions) Unrealized (losses)/gains included in operating revenues $ (98 ) $ 104 Unrealized gains/(losses) included in cost of operations 302 (137 ) Total impact to statement of operations — energy commodities $ 204 $ (33 ) Total impact to statement of operations — interest rate contracts $ 48 $ 5

Debt and Capital Leases (Tables

Debt and Capital Leases (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-term debt and capital leases	Long-term debt and capital leases consisted of the following: (In millions, except rates) March 31, 2018 December 31, 2017 March 31, 2018 interest rate % (a) Recourse debt: Senior notes, due 2022 992 992 6.250 Senior notes, due 2024 733 733 6.250 Senior notes, due 2026 1,000 1,000 7.250 Senior notes, due 2027 1,250 1,250 6.625 Senior notes, due 2028 870 870 5.750 Term loan facility, due 2023 1,867 1,872 L+1.75 Tax-exempt bonds 465 465 4.125 - 6.00 Subtotal recourse debt 7,177 7,182 Non-recourse debt: NRG Yield, Inc. Convertible Senior Notes, due 2019 345 345 3.500 NRG Yield, Inc. Convertible Senior Notes, due 2020 288 288 3.250 NRG Yield Operating LLC Senior Notes, due 2024 500 500 5.375 NRG Yield Operating LLC Senior Notes, due 2026 350 350 5.000 NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2023 (b) 75 55 L+2.500 El Segundo Energy Center, due 2023 369 400 L+1.75 - L+2.375 Marsh Landing, due 2023 309 318 L+2.125 Alta Wind I - V lease financing arrangements, due 2034 and 2035 926 926 5.696 - 7.015 Walnut Creek, term loans due 2023 259 267 L+1.625 Utah Portfolio, due 2022 278 278 various Tapestry, due 2021 158 162 L+1.625 CVSR, due 2037 731 746 2.339 - 3.775 CVSR HoldCo, due 2037 188 194 4.680 Alpine, due 2022 135 135 L+1.750 Energy Center Minneapolis, due 2025 83 83 5.95 Energy Center Minneapolis, due 2031 125 125 3.55 Viento, due 2023 163 163 L+3.00 Buckthorn Solar, due 2018 and 2025 183 169 L+1.750 NRG Yield - other 573 579 various Subtotal NRG Yield debt (non-recourse to NRG) (c) 6,038 6,083 Ivanpah, due 2033 and 2038 1,068 1,073 2.285 - 4.256 Carlsbad Energy Project (c) 475 427 L+1.625 - 4.120 Agua Caliente, due 2037 815 818 2.395 - 3.633 Agua Caliente Borrower 1, due 2038 86 89 5.430 Cedro Hill, due 2025 (c) 149 151 L+1.75 Midwest Generation, due 2019 132 152 4.390 NRG Other Renewables (c) 466 478 various NRG Other 178 180 various Subtotal other NRG non-recourse debt 3,369 3,368 Subtotal all non-recourse debt 9,407 9,451 Subtotal long-term debt (including current maturities) 16,584 16,633 Capital leases 4 5 various Subtotal long-term debt and capital leases (including current maturities) 16,588 16,638 Less current maturities (d) (956 ) (688 ) Less debt issuance costs (201 ) (204 ) Discounts (25 ) (30 ) Total long-term debt and capital leases $ 15,406 $ 15,716 (a) As of March 31, 2018 , L+ equals 3 month LIBOR plus x%, except for the 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) Debt associated with the asset sales announced in February 2018 (d) The NRG Yield, Inc. Convertible Senior Notes, due 2019, become due in February 2019 and are recorded in current maturities as of March 31, 2018.

Variable Interest Entities, o32

Variable Interest Entities, or VIEs (Tables)	3 Months Ended
	Mar. 31, 2018
Variable Interest Entities Disclosure [Abstract]
Financial Information for Consolidated VIEs	The summarized financial information for the Company's consolidated VIEs consisted of the following: (In millions) March 31, 2018 December 31, 2017 Current assets $ 171 $ 118 Net property, plant and equipment 2,712 2,337 Other long-term assets 665 658 Total assets 3,548 3,113 Current liabilities 111 96 Long-term debt 856 661 Other long-term liabilities 211 209 Total liabilities 1,178 966 Redeemable noncontrolling interest 80 78 Noncontrolling interests 646 507 Net assets less noncontrolling interests $ 1,644 $ 1,562

Changes in Capital Structure (T

Changes in Capital Structure (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Changes in NRG's common shares issued and outstanding	The following table reflects the changes in NRG's common stock issued and outstanding: Issued Treasury Outstanding Balance as of December 31, 2017 418,323,134 (101,580,045 ) 316,743,089 Shares issued under LTIPs 1,081,994 — 1,081,994 Shares issued under ESPP — 175,862 175,862 Shares repurchased — (3,114,748 ) (3,114,748 ) Balance as of March 31, 2018 419,405,128 (104,518,931 ) 314,886,197
Shares Repurchased	March 2018 , share repurchases were made as follows: Total number of shares purchased Average price paid per share (a) Amounts paid for shares purchased (in millions) (a) Board Authorized Share Repurchases March 2018 3,114,748 $ 29.75 $ 93 (a) The average price paid per share and amounts paid for shares purchased exclude the commissions of $0.01 per share paid in connection with the share repurchase.
Schedule of dividends paid	The following table lists the dividends paid during the three months ended March 31, 2018 : First Quarter 2018 Dividends per Common Share $ 0.03

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of segment reporting information, by segment	Retail (a) Generation (a) Renewables (a) NRG Yield Corporate (a) Eliminations Total Three months ended March 31, 2018 (In millions) Operating revenues (a) $ 1,481 $ 327 $ 86 $ 225 $ 2 $ 300 $ 2,421 Depreciation and amortization 28 67 51 81 8 — 235 Reorganization costs 3 4 — — 13 — 20 Equity in earnings/(losses) of unconsolidated affiliates — 2 — 4 (1 ) (7 ) (2 ) Income/(loss) from continuing operations before income taxes 946 (536 ) (40 ) (1 ) (126 ) (11 ) 232 Income/(loss) from continuing operations 946 (536 ) (34 ) — (132 ) (11 ) 233 Net Income/(Loss) 946 (536 ) (34 ) — (132 ) (11 ) 233 Net Income/(Loss) attributable to NRG Energy, Inc. $ 940 $ (536 ) $ 1 $ 21 — $ (148 ) $ 1 $ 279 Total assets as of March 31, 2018 $ 3,521 $ 7,313 $ 5,191 $ 8,362 $ 9,108 $ (9,743 ) $ 23,752 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 1 $ (307 ) $ 8 $ — $ (2 ) $ — $ (300 ) Retail (a) Generation (a) Renewables (a) NRG Yield Corporate (a)(b) Eliminations Total Three months ended March 31, 2017 (In millions) Operating revenues (a) $ 1,335 $ 965 $ 95 $ 221 $ 10 $ (244 ) $ 2,382 Depreciation and amortization 28 97 47 77 8 — 257 Equity in (losses)/earnings of unconsolidated affiliates — (13 ) — 19 3 (4 ) 5 (Loss)/income from continuing operations before income taxes (31 ) 37 (35 ) (3 ) (137 ) (4 ) (173 ) (Loss)/income from continuing operations (34 ) 37 (29 ) (2 ) (137 ) (4 ) (169 ) Loss from discontinued operations, net of tax — — — — (34 ) — (34 ) Net (Loss)/Income (34 ) 37 (29 ) (2 ) (171 ) (4 ) (203 ) Net (Loss)/Income attributable to NRG Energy, Inc. $ (33 ) $ 37 $ (1 ) $ 12 $ (171 ) $ (7 ) $ (163 ) (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 1 $ 209 $ 8 $ — $ 26 $ — $ 244 (b) Includes other income - affiliate $ — $ — $ — $ — $ 48 $ — $ 48

Earnings_(Loss) Per Share (Tabl

Earnings/(Loss) Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Reconciliation of NRG's basic and diluted earnings per share	The reconciliation of NRG's basic and diluted loss per share is shown in the following table: Three months ended March 31, (In millions, except per share data) 2018 2017 Basic income/(loss) per share attributable to NRG Energy, Inc. common stockholders Net income/(loss) attributable to NRG Energy, Inc. $ 279 $ (163 ) Weighted average number of common shares outstanding - basic 318 316 Earnings/(loss) per weighted average common share — basic $ 0.88 $ (0.52 ) Diluted income/(loss) per share attributable to NRG Energy, Inc. common stockholders Weighted average number of common shares outstanding - diluted 318 316 Incremental shares attributable to the issuance of equity compensation (treasury stock method) 4 — Total dilutive shares 322 316 Earnings/(loss) per weighted average common share — diluted $ 0.87 $ (0.52 )
Summary of NRG's outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company's diluted earnings per share	The following table summarizes NRG’s outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company’s diluted loss per share: Three months ended March 31, (In millions of shares) 2018 2017 Equity compensation plans 1 6 Total 1 6

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The income tax provision consisted of the following: Three months ended March 31, (In millions except otherwise noted) 2018 2017 Income/(Loss) before income taxes $ 232 $ (173 ) Income tax benefit from continuing operations (1 ) (4 ) Effective tax rate (0.4 )% 2.3 %

Condensed Consolidating Finan37

Condensed Consolidating Financial Information (Tables)	3 Months Ended
	Mar. 31, 2018
Condensed Consolidating Financial Information Disclosure [Abstract]
Condensed Consolidating Statements of Operations	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 1,483 $ 885 $ — $ 53 $ 2,421 Operating Costs and Expenses Cost of operations 1,082 409 14 53 1,558 Depreciation and amortization 73 154 8 — 235 Selling, general and administrative 98 32 61 — 191 Reorganization costs 2 — 18 — 20 Development costs — 9 4 — 13 Total operating costs and expenses 1,255 604 105 53 2,017 Gain/(loss) on sale of assets 3 (1 ) — — 2 Operating Income/(Loss) 231 280 (105 ) — 406 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 210 — 330 (540 ) — Equity in losses of unconsolidated affiliates — (1 ) (1 ) — (2 ) Other income/(expense), net 21 (11 ) 3 (16 ) (3 ) Loss on debt extinguishment, net — — (2 ) — (2 ) Interest expense (3 ) (72 ) (92 ) (167 ) Total other income/(expense) 228 (84 ) 238 (556 ) (174 ) Income Before Income Taxes 459 196 133 (556 ) 232 Income tax expense/(benefit) 113 48 (162 ) — (1 ) Net Income 346 148 295 (556 ) 233 Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests — (46 ) 16 (16 ) (46 ) Net Income Attributable to NRG Energy, Inc. $ 346 $ 194 $ 279 $ (540 ) $ 279 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended March 31, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 1,599 $ 867 $ — $ (84 ) $ 2,382 Operating Costs and Expenses Cost of operations 1,260 664 18 (80 ) 1,862 Depreciation and amortization 99 150 8 — 257 Selling, general and administrative 96 46 118 — 260 Development costs — 12 5 — 17 Total operating costs and expenses 1,455 872 149 (80 ) 2,396 Other income - affiliate — — 48 — 48 Gain on sale of assets 2 — — — 2 Operating Income/(Loss) 146 (5 ) (101 ) (4 ) 36 Other (Expense)/Income Equity in (losses)/earnings of consolidated subsidiaries (42 ) 1 68 (27 ) — Equity in (losses)/earnings of unconsolidated affiliates (1 ) 7 (1 ) — 5 Other (expense)/income, net (2 ) 5 7 3 13 Loss on debt extinguishment, net — (2 ) — — (2 ) Interest expense (4 ) (104 ) (117 ) — (225 ) Total other expense (49 ) (93 ) (43 ) (24 ) (209 ) Income/(Loss) from Continuing Operations Before Income Taxes 97 (98 ) (144 ) (28 ) (173 ) Income tax expense/(benefit) 19 (46 ) 25 (2 ) (4 ) Income/(Loss) from Continuing Operations 78 (52 ) (169 ) (26 ) (169 ) (Loss)/income from discontinued operations, net of income tax — (37 ) 3 — (34 ) Net Income/(Loss) 78 (89 ) (166 ) (26 ) (203 ) Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interest — (38 ) (3 ) 1 (40 ) Net Income/(Loss) Attributable to NRG Energy, Inc. $ 78 $ (51 ) $ (163 ) $ (27 ) $ (163 ) (a) All significant intercompany transactions have been eliminated in consolidation.
Condensed Consolidating Statements of Comprehensive Income/(Loss)	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME For the three months ended March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income $ 346 $ 148 $ 295 $ (556 ) $ 233 Other Comprehensive (Loss)/Income, net of tax Unrealized gain on derivatives, net — 16 15 (17 ) 14 Foreign currency translation adjustments, net (2 ) (2 ) (3 ) 5 (2 ) Defined benefit plans, net — — (1 ) — (1 ) Other comprehensive (loss)/income (2 ) 14 11 (12 ) 11 Comprehensive Income 344 162 306 (568 ) 244 Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (46 ) 24 (16 ) (38 ) Comprehensive Income Attributable to NRG Energy, Inc. $ 344 $ 208 $ 282 $ (552 ) $ 282 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) For the three months ended March 31, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income/(Loss) $ 78 $ (89 ) $ (166 ) $ (26 ) $ (203 ) Other Comprehensive Income, net of tax Unrealized gain on derivatives, net — 5 4 (5 ) 4 Foreign currency translation adjustments, net 5 4 7 (9 ) 7 Defined benefit plans, net — 1 (1 ) — — Other comprehensive income 5 10 10 (14 ) 11 Comprehensive Income/(Loss) 83 (79 ) (156 ) (40 ) (192 ) Less: Comprehensive loss attributable to noncontrolling interest and redeemable noncontrolling interest — (37 ) (3 ) 1 (39 ) Comprehensive Income/(Loss) Attributable to NRG Energy, Inc. $ 83 $ (42 ) $ (153 ) $ (41 ) $ (153 ) (a) All significant intercompany transactions have been eliminated in consolidation.
Condensed Consolidating Balance Sheets	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated ASSETS (In millions) Current Assets Cash and cash equivalents $ 43 $ 371 $ 350 $ — $ 764 Funds deposited by counterparties 241 — — — 241 Restricted cash 8 399 — — 407 Accounts receivable, net 610 290 3 — 903 Inventory 323 205 — — 528 Derivative instruments 932 207 12 (136 ) 1,015 Cash collateral paid in support of energy risk management activities 211 — — — 211 Accounts receivable - affiliate 509 141 491 (1,068 ) 73 Current assets - held for sale — 89 — — 89 Prepayments and other current assets 154 134 38 — 326 Total current assets 3,031 1,836 894 (1,204 ) 4,557 Property, plant and equipment, net 2,500 11,196 240 (25 ) 13,911 Other Assets Investment in subsidiaries 511 1 7,374 (7,886 ) — Equity investments in affiliates — 1,010 1 — 1,011 Goodwill 360 179 — — 539 Intangible assets, net 439 1,290 — (3 ) 1,726 Nuclear decommissioning trust fund 680 — — — 680 Derivative instruments 245 118 38 (47 ) 354 Deferred income tax 264 (34 ) (94 ) — 136 Non-current assets held-for-sale — 157 — — 157 Other non-current assets 73 489 119 — 681 Total other assets 2,572 3,210 7,438 (7,936 ) 5,284 Total Assets $ 8,103 $ 16,242 $ 8,572 $ (9,165 ) $ 23,752 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 935 $ 21 $ — $ 956 Accounts payable 510 241 36 — 787 Accounts payable — affiliate 1,662 (121 ) (441 ) (1,068 ) 32 Derivative instruments 857 69 — (136 ) 790 Cash collateral received in support of energy risk management activities 240 — — — 240 Current liabilities held-for-sale — 80 — — 80 Accrued expenses and other current liabilities 236 146 280 — 662 Accrued expenses and other current liabilities-affiliate — — 161 — 161 Total current liabilities 3,505 1,350 57 (1,204 ) 3,708 Other Liabilities Long-term debt and capital leases 244 8,387 6,775 — 15,406 Nuclear decommissioning reserve 272 — — — 272 Nuclear decommissioning trust liability 400 — — — 400 Deferred income taxes 112 64 (156 ) — 20 Derivative instruments 224 87 — (47 ) 264 Out-of-market contracts, net 62 139 — — 201 Non-current liabilities held-for-sale — 7 — — 7 Other non-current liabilities 419 324 393 — 1,136 Total non-current liabilities 1,733 9,008 7,012 (47 ) 17,706 Total liabilities 5,238 10,358 7,069 (1,251 ) 21,414 Redeemable noncontrolling interest in subsidiaries — 80 — — 80 Stockholders’ Equity 2,865 5,804 1,503 (7,914 ) 2,258 Total Liabilities and Stockholders’ Equity $ 8,103 $ 16,242 $ 8,572 $ (9,165 ) $ 23,752 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS December 31, 2017 Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated ASSETS (In millions) Current Assets Cash and cash equivalents $ — $ 348 $ 643 $ — $ 991 Funds deposited by counterparties 37 — — — 37 Restricted cash 4 504 — — 508 Accounts receivable, net 768 307 4 — 1,079 Inventory 338 194 — — 532 Derivative instruments 625 81 9 (89 ) 626 Cash collateral paid in support of energy risk management activities 170 1 — — 171 Accounts receivable - affiliate 709 213 (129 ) (698 ) 95 Current assets held-for-sale 8 107 — — 115 Prepayments and other current assets 116 118 27 — 261 Total current assets 2,775 1,873 554 (787 ) 4,415 Property, plant and equipment, net 2,502 11,194 238 (26 ) 13,908 Other Assets Investment in subsidiaries 305 — 7,581 (7,886 ) — Equity investments in affiliates — 1,036 2 — 1,038 Goodwill 360 179 — — 539 Intangible assets, net 454 1,295 — (3 ) 1,746 Nuclear decommissioning trust fund 692 — — — 692 Derivative instruments 121 40 31 (20 ) 172 Deferred income taxes 377 (7 ) (236 ) — 134 Non-current assets held for sale — 43 — — 43 Other non-current assets 50 461 158 (38 ) 631 Total other assets 2,359 3,047 7,536 (7,947 ) 4,995 Total Assets $ 7,636 $ 16,114 $ 8,328 $ (8,760 ) $ 23,318 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 667 $ 59 $ (38 ) $ 688 Accounts payable 545 281 55 — 881 Accounts payable — affiliate 751 (201 ) 181 (698 ) 33 Derivative instruments 535 108 — (88 ) 555 Cash collateral received in support of energy risk management activities 37 — — — 37 Current liabilities held-for-sale — 72 — — 72 Accrued expenses and other current liabilities 290 175 425 — 890 Accrued expenses and other current liabilities - affiliate — — 161 — 161 Total current liabilities 2,158 1,102 881 (824 ) 3,317 Other Liabilities Long-term debt and capital leases 244 8,733 6,739 — 15,716 Nuclear decommissioning reserve 269 — — — 269 Nuclear decommissioning trust liability 415 — — — 415 Deferred income taxes 112 64 (155 ) — 21 Derivative instruments 110 107 — (20 ) 197 Out-of-market contracts, net 66 141 — — 207 Non-current liabilities held-for-sale — 8 — — 8 Other non-current liabilities 410 321 391 — 1,122 Total non-current liabilities 1,626 9,374 6,975 (20 ) 17,955 Total Liabilities 3,784 10,476 7,856 (844 ) 21,272 Redeemable noncontrolling interest in subsidiaries — 78 — — 78 Stockholders’ Equity 3,852 5,560 472 (7,916 ) 1,968 Total Liabilities and Stockholders’ Equity $ 7,636 $ 16,114 $ 8,328 $ (8,760 ) $ 23,318 (a) All significant intercompany transactions have been eliminated in consolidation.
Condensed Consolidating Statements of Cash Flows	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the three months ended March 31, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income $ 346 $ 148 $ 295 $ (556 ) $ 233 Adjustments to reconcile net income to net cash provided/(used) by operating activities: Distributions from unconsolidated affiliates — 13 — (3 ) 10 Equity in losses of unconsolidated affiliates — 1 1 — 2 Depreciation and amortization 73 154 8 — 235 Provision for bad debts 17 (2 ) — — 15 Amortization of nuclear fuel 13 — — — 13 Amortization of financing costs and debt discount/premiums — 10 4 — 14 Adjustment for debt extinguishment — — 2 — 2 Amortization of intangibles and out-of-market contracts 3 19 — — 22 Amortization of unearned equity compensation — — 13 — 13 Changes in deferred income taxes and liability for uncertain tax benefits 114 27 (144 ) — (3 ) Changes in nuclear decommissioning trust liability 34 — — — 34 Changes in derivative instruments 5 (220 ) (14 ) (18 ) (247 ) Changes in collateral deposits in support of energy risk management activities 162 1 — — 163 Gain on sale of emission allowances (8 ) — — — (8 ) (Gain)/loss on sale of assets (3 ) 1 — — (2 ) Changes in other working capital (442 ) 22 (296 ) 577 (139 ) Net Cash Provided/(Used) by Operating Activities 314 174 (131 ) — 357 Cash Flows from Investing Activities Dividends from NRG Yield, Inc. — — 25 (25 ) — Acquisition of Drop Down Assets, net of cash acquired — (42 ) — 42 — Acquisition of business, net of cash acquired (2 ) (60 ) — — (62 ) Capital expenditures (61 ) (276 ) (21 ) — (358 ) Decrease in notes receivable — 3 — — 3 Purchases of emission allowances (17 ) — — — (17 ) Proceeds from sale of emission allowances 23 — — — 23 Investments in nuclear decommissioning trust fund securities (216 ) — — — (216 ) Proceeds from the sale of nuclear decommissioning trust fund securities 182 — — — 182 Proceeds from sale of assets, net of cash disposed of 10 1 — — 11 Change in investments in unconsolidated affiliates — 2 — — 2 Net Cash (Used)/Provided by Investing Activities (81 ) (372 ) 4 17 (432 ) Cash Flows from Financing Activities Dividends from NRG Yield, Inc. — (25 ) — 25 — Payment from/(for) intercompany loans 18 80 (98 ) — — Acquisition of Drop Down Assets, net of cash acquired — — 42 (42 ) — Payment of dividends to common and preferred stockholders — — (10 ) — (10 ) Payment for treasury stock — — (93 ) — (93 ) Proceeds from issuance of long-term debt — 179 — — 179 Payments for short and long-term debt — (222 ) (6 ) — (228 ) Contributions from, net of distributions to noncontrolling interests in subsidiaries — 110 — — 110 Payment of debt issuance costs — (6 ) (1 ) — (7 ) Net Cash Provided/(Used) by Financing Activities 18 116 (166 ) (17 ) (49 ) Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash 251 (82 ) (293 ) — (124 ) Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 41 852 643 — 1,536 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 292 $ 770 $ 350 $ — $ 1,412 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the three months ended March 31, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income/(loss) $ 78 $ (89 ) $ (166 ) $ (26 ) $ (203 ) (Loss)/income from discontinued operations — (37 ) 3 — (34 ) Net income/(loss) from continuing operations 78 (52 ) (169 ) (26 ) (169 ) Adjustments to reconcile net income/(loss) to net cash (used)/provided by operating activities: Distributions from unconsolidated affiliates — 18 — (5 ) 13 Equity in losses/(earnings) of unconsolidated affiliates 1 (7 ) 1 — (5 ) Depreciation and amortization 99 150 8 — 257 Provision for bad debts 8 1 — — 9 Amortization of nuclear fuel 12 — — — 12 Amortization of financing costs and debt discount/premiums — 11 4 — 15 Amortization of intangibles and out-of-market contracts 6 24 — — 30 Amortization of unearned equity compensation — — 8 — 8 Changes in deferred income taxes and liability for uncertain tax benefits 19 (46 ) 28 — 1 Changes in nuclear decommissioning trust liability 36 — — — 36 Changes in derivative instruments (4 ) 43 (1 ) — 38 Changes in collateral deposits in support of energy risk management activities (136 ) 9 — — (127 ) Gain on sale of assets (2 ) — — — (2 ) Changes in other working capital (118 ) 458 (601 ) 63 (198 ) Net cash (used)/provided by continuing operations (1 ) 609 (722 ) 32 (82 ) Cash provided by discontinued operations — 15 — — 15 Net Cash (Used)/Provided by Operating Activities (1 ) 624 (722 ) 32 (67 ) Cash Flows from Investing Activities Dividends from NRG Yield, Inc. — — 22 (22 ) — Intercompany dividends — — 129 (129 ) — Acquisition of Drop Down Assets, net of cash acquired — (131 ) — 131 — Acquisition of businesses, net of cash acquired — (3 ) — — (3 ) Capital expenditures (64 ) (168 ) (4 ) — (236 ) Decrease in notes receivable — 4 — — 4 Purchases of emission allowances (9 ) — — — (9 ) Proceeds from sale of emission allowances 11 — — — 11 Investments in nuclear decommissioning trust fund securities (153 ) — — — (153 ) Proceeds from the sale of nuclear decommissioning trust fund securities 117 — — — 117 Proceeds from sale of assets, net of cash disposed of 11 3 — — 14 Change in investments in unconsolidated affiliates — (12 ) — — (12 ) Other 18 — — — 18 Net cash (used)/provided by continuing operations (69 ) (307 ) 147 (20 ) (249 ) Cash used by discontinued operations — (32 ) — — (32 ) Net Cash (Used)/Provided by Investing Activities (69 ) (339 ) 147 (20 ) (281 ) Cash Flows from Financing Activities Dividends from NRG Yield, Inc. — (22 ) — 22 — Payments (for)/from intercompany loans 65 (428 ) 395 (32 ) — Acquisition of Drop Down Assets, net of cash acquired — — 131 (131 ) — Intercompany dividends — (129 ) — 129 — Payment of dividends to common and preferred stockholders — — (9 ) — (9 ) Net receipts from settlement of acquired derivatives that include financing elements — 1 — — 1 Proceeds from issuance of long-term debt — 167 26 — 193 Payments for short and long-term debt — (146 ) (31 ) — (177 ) Distributions to, net of contributions from, noncontrolling interests in subsidiaries — (5 ) — — (5 ) Payment of debt issuance costs — (10 ) (4 ) — (14 ) Other - contingent consideration — (10 ) — — (10 ) Net cash provided/(used) by continuing operations 65 (582 ) 508 (12 ) (21 ) Cash used by discontinued operations — (132 ) — — (132 ) Net Cash Provided/(Used) by Financing Activities 65 (714 ) 508 (12 ) (153 ) Effect of exchange rate changes on cash and cash equivalents — (7 ) — — (7 ) Change in cash from discontinued operations — (149 ) — — (149 ) Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash (5 ) (287 ) (67 ) — (359 ) Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 13 1,050 323 — 1,386 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 8 $ 763 $ 256 $ — $ 1,027 (a) All significant intercompany transactions have been eliminated in consolidation.

Basis of Presentation - Basis o

Basis of Presentation - Basis of Presentation (Details)	Mar. 31, 2018MW
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Generation capacity (in MW)	30,000

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Other Balance Sheet Information (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accounts receivable allowance for doubtful accounts	$ 27	$ 28
Property, plant and equipment accumulated depreciation	4,679	4,465
Intangible assets accumulated amortization	1,393	1,818
Out-of-market contracts accumulated amortization	$ 364	$ 358

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 764	$ 991	$ 627	$ 938
Funds deposited by counterparties	241	37	3	2
Restricted cash	407	508	397	446
Cash and cash equivalents, funds deposited by counterparties and restricted cash shown in the statement of cash flows	$ 1,412	$ 1,536	$ 1,027	$ 1,386

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Noncontrolling Interest [Roll Forward]
Balance as of beginning of period	$ 2,314
Dividends paid to NRG Yield, Inc. public shareholders	(30)
Distributions to noncontrolling interest	(19)
Comprehensive income (loss) attributable to noncontrolling interest	(38)	$ (39)
Contributions from noncontrolling interest	147
Sale of assets to NRG Yield, Inc.	(4)
Balance as of end of period	2,392
Noncontrolling Interest
Noncontrolling Interest [Roll Forward]
Comprehensive income (loss) attributable to noncontrolling interest	(22)
Non-cash adjustments to noncontrolling interest	$ 6

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Noncontrolling Interest [Line Items]
Balance as of beginning of period	$ 78
Distributions to noncontrolling interest	(19)
Contributions from redeemable noncontrolling interest	12
Comprehensive income (loss) attributable to noncontrolling interest	(38)	$ (39)
Balance as of end of period	80
Redeemable noncontrolling interest
Noncontrolling Interest [Line Items]
Distributions to noncontrolling interest	(1)
Non-cash adjustments to noncontrolling interest	7
Comprehensive income (loss) attributable to noncontrolling interest	$ (16)

Summary of Significant Accoun43

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to opening retained earnings	$ (5,982)		$ (6,268)
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to opening retained earnings		$ 16

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Capacity Revenue (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from External Customer [Line Items]
Estimated revenue for cleared auction MWs, capacity auctions	$ 1,823
Capacity revenue
Revenue from External Customer [Line Items]
Estimated revenue for cleared auction MWs, capacity auctions	$ 288
Scenario, Forecast | Capacity revenue
Revenue from External Customer [Line Items]
Estimated revenue for cleared auction MWs, capacity auctions		$ 57	$ 222	$ 423	$ 508	$ 554

Summary of Significant Accoun45

Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,823
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	196	$ (19)
Derivative revenue	204	(33)
Contract amortization	(14)
Operating revenues	2,421	2,382
Lease revenue	252
Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(182)
Contract amortization	0
Operating revenues	300	(244)
Lease revenue	0
Energy revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	619
Derivative revenue	432
Lease revenue	163
Energy revenue | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(161)
Derivative revenue	0
Lease revenue	0
Capacity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	288
Derivative revenue	26
Lease revenue	79
Capacity revenue | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(1)
Derivative revenue	0
Lease revenue	0
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Retail | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Retail | Mass customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,170
Retail | Mass customers | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(1)
Retail | Business solutions customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	316
Retail | Business solutions customers | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Total retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,486
Total retail revenue | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(1)
Derivative revenue
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	(106)
Derivative revenue	360
Derivative revenue | Eliminations
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	484
Derivative revenue	484
Other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	148
Lease revenue	10
Other revenue | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(19)
Lease revenue	0
Total operating revenue
Disaggregation of Revenue [Line Items]
Operating revenues	2,421
Total operating revenue | Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	302
Other derivative revenue
Disaggregation of Revenue [Line Items]
Derivative revenue	8
Other derivative revenue | Eliminations
Disaggregation of Revenue [Line Items]
Derivative revenue	0
Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,481
Contract amortization	0
Operating revenues	1,481	1,335
Lease revenue	6
Retail | Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(1)	(1)
Retail | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Derivative revenue	0
Lease revenue	0
Retail | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Derivative revenue	0
Lease revenue	0
Retail | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Retail | Retail | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,171
Retail | Retail | Business solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	316
Retail | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,487
Retail | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	(6)
Derivative revenue	(6)
Retail | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Lease revenue	6
Retail | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	1,481
Retail | Other derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	0
Generation | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	431
Contract amortization	3
Operating revenues	327	965
Lease revenue	1
Generation | Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	307	(209)
Generation | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	589
Derivative revenue	432
Lease revenue	0
Generation | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	207
Derivative revenue	26
Lease revenue	0
Generation | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Generation | Retail | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | Retail | Business solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	(574)
Derivative revenue	(108)
Generation | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	102
Lease revenue	1
Generation | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	327
Generation | Other derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	8
Generation | Gulf Coast | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	148
Contract amortization	3
Lease revenue	0
Generation | Gulf Coast | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	371
Derivative revenue	371
Lease revenue	0
Generation | Gulf Coast | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	67
Derivative revenue	0
Lease revenue	0
Generation | Gulf Coast | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Generation | Gulf Coast | Retail | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | Gulf Coast | Retail | Business solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | Gulf Coast | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | Gulf Coast | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	(564)
Derivative revenue	(188)
Generation | Gulf Coast | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	86
Lease revenue	0
Generation | Gulf Coast | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	(37)
Generation | Gulf Coast | Other derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	5
Generation | East and West | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	283
Contract amortization	0
Lease revenue	1
Generation | East and West | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	218
Derivative revenue	61
Lease revenue	0
Generation | East and West | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	140
Derivative revenue	26
Lease revenue	0
Generation | East and West | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Generation | East and West | Retail | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | East and West | Retail | Business solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | East and West | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Generation | East and West | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	(10)
Derivative revenue	80
Generation | East and West | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	16
Lease revenue	1
Generation | East and West | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	364
Generation | East and West | Other derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	3
Renewables | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	32
Contract amortization	0
Operating revenues	86	95
Lease revenue	64
Renewables | Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(8)	(8)
Renewables | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	77
Derivative revenue	0
Lease revenue	61
Renewables | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Derivative revenue	0
Lease revenue	0
Renewables | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Renewables | Retail | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Renewables | Retail | Business solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Renewables | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Renewables | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	(10)
Derivative revenue	(10)
Renewables | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	19
Lease revenue	3
Renewables | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	86
Renewables | Other derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	0
NRG Yield | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	61
Contract amortization	(17)
Operating revenues	225	221
Lease revenue	181
NRG Yield | Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	0	$ 0
NRG Yield | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	114
Derivative revenue	0
Lease revenue	102
NRG Yield | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	82
Derivative revenue	0
Lease revenue	79
NRG Yield | Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
NRG Yield | Retail | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
NRG Yield | Retail | Business solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
NRG Yield | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
NRG Yield | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Unrealized Gain (Loss) on Derivatives, Mark To Market, Economic Hedging Activities	0
Derivative revenue	0
NRG Yield | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	46
Lease revenue	0
NRG Yield | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	225
NRG Yield | Other derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	$ 0

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Contract Assets and Liabilities (Details) $ in Millions	Mar. 31, 2018USD ($)
Schedule Of Contract Assets And Liabilities [Line Items]
Deferred customer acquisition costs	$ 85
Total accounts receivable, net	903
Unbilled revenues (included within Accounts receivable, net - Contracts with customers)	292
Deferred revenues	63
Accounts receivable, net - Contracts with customers
Schedule Of Contract Assets And Liabilities [Line Items]
Total accounts receivable, net	784
Accounts receivable, net - Leases
Schedule Of Contract Assets And Liabilities [Line Items]
Total accounts receivable, net	81
Accounts receivable, net - Derivative instruments
Schedule Of Contract Assets And Liabilities [Line Items]
Total accounts receivable, net	$ 38

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Recent Accounting Developments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of operations	$ 1,558	$ 1,862
Other income/(expense), net	$ (3)	13
ASU 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of operations		4
Other income/(expense), net		$ 4

Discontinued Operations and D48

Discontinued Operations and Dispositions - Summary of Results (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations, net of tax	$ 0	$ (34)
Discontinued Operations | GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues		381
Operating costs and expenses		(373)
Other expenses		(44)
Loss from operations of discontinued components, before tax		(36)
Income tax expense		1
Loss from operations of discontinued components		(37)
Interest income - affiliate		3
Loss from discontinued operations, net of tax		$ (34)

Discontinued Operations and D49

Discontinued Operations and Dispositions - Narrative (Details) - USD ($) $ in Millions	Apr. 27, 2018	Mar. 22, 2018	Jun. 12, 2017	Dec. 31, 2017	Dec. 31, 2017	Mar. 31, 2018
GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pension liability						$ 91
Liability, other postretirement-employment and retiree heal and welfare benefits						25
GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Settlement consideration						$ 261.3
GenOn Entities | Services Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Shared services, annualized rate				$ 84	$ 84
Credit applied			$ 28
Restructuring Support Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of aggregate principal amount						93.00%
Intercompany secured revolving credit facility						$ 125
Payment of pension contributions				13	13
Restructuring Support Agreement | Services Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Shared services, annualized rate				84	84
Credit applied					$ 28
Restructuring Support Agreement | Services Agreement | GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payment to affiliate		$ 13.5		$ 15
Subsequent Event | GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Professional fees	$ 6
Subsequent Event | Restructuring Support Agreement | GenOn Mid-Atlantic | Intercompany Credit Agreement | Letter of Credit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Letters of credit	$ 37.5

Discontinued Operations and D50

Discontinued Operations and Dispositions - Transfer of Assets Under Common Control (Details) $ in Millions	Mar. 30, 2018USD ($)MW	Mar. 31, 2018USD ($)MW	Mar. 27, 2017USD ($)MW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generation capacity (in MW) | MW		30,000
Contributions from noncontrolling interest		$ 147
Buckthorn Renewables, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generation capacity (in MW) | MW	154
Cash consideration	$ 42
Assumed non-recourse debt in transaction	183
Contributions from noncontrolling interest	$ 19
Agua Caliente solar project
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration			$ 130
Assumed non-recourse debt in transaction			328
Working capital adjustments			$ 1
Agua Caliente solar project | Agua Caliente
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of ownership sold			16.00%
Generation capacity (in MW) | MW			46
Agua Caliente solar project | Utah Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generation capacity (in MW) | MW			265
Discontinued Operations, Held-for-sale or Disposed of by Sale | Buckthorn Renewables, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of ownership sold	100.00%

Fair Value of Financial Instr51

Fair Value of Financial Instruments - Estimated Carrying Amounts and Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term debt, including current portion	$ 16,584	$ 16,633
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes receivable	15	16
Long-term debt, including current portion	16,559	16,603
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes receivable	14	15
Long-term debt, including current portion	16,687	16,894
Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term debt, including current portion	8,772	8,934
Fair Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term debt, including current portion	$ 7,915	$ 7,960

Fair Value of Financial Instr52

Fair Value of Financial Instruments - Assets and liabilities measured and recorded at fair value (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 1,369	$ 798
Derivative liabilities	1,054	752
Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1,277	745
Derivative liabilities	1,024	693
Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	92	53
Derivative liabilities	30	59
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	22	22
U.S. government and federal agency obligations	1	1
Total assets	2,072	1,513
Derivative liabilities	1,054	752
Fair value, measurements, recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1,277	745
Derivative liabilities	1,024	693
Fair value, measurements, recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	92	53
Derivative liabilities	30	59
Fair value, measurements, recurring | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	16	47
Fair value, measurements, recurring | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	56	43
Fair value, measurements, recurring | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	92	82
Fair value, measurements, recurring | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	16	14
Fair value, measurements, recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	100	99
Fair value, measurements, recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	333	334
Equity contracts	62	68
Fair value, measurements, recurring | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	5	5
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	3	3
U.S. government and federal agency obligations	1	1
Total assets	576	616
Derivative liabilities	224	257
Fair value, measurements, recurring | Level 1 | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	168	191
Derivative liabilities	224	257
Fair value, measurements, recurring | Level 1 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair value, measurements, recurring | Level 1 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	16	45
Fair value, measurements, recurring | Level 1 | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	55	42
Fair value, measurements, recurring | Level 1 | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 1 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 1 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	333	334
Fair value, measurements, recurring | Level 1 | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	0	0
U.S. government and federal agency obligations	0	0
Total assets	1,366	765
Derivative liabilities	759	418
Fair value, measurements, recurring | Level 2 | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1,060	509
Derivative liabilities	729	359
Fair value, measurements, recurring | Level 2 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	92	53
Derivative liabilities	30	59
Fair value, measurements, recurring | Level 2 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	2
Fair value, measurements, recurring | Level 2 | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	1	1
Fair value, measurements, recurring | Level 2 | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	92	82
Fair value, measurements, recurring | Level 2 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	16	14
Fair value, measurements, recurring | Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	100	99
Fair value, measurements, recurring | Level 2 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 2 | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	5	5
Fair value, measurements, recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	19	19
U.S. government and federal agency obligations	0	0
Total assets	68	64
Derivative liabilities	71	77
Fair value, measurements, recurring | Level 3 | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	49	45
Derivative liabilities	71	77
Fair value, measurements, recurring | Level 3 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair value, measurements, recurring | Level 3 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	$ 0	$ 0

Fair Value of Financial Instr53

Fair Value of Financial Instruments - Reconciliation of Level 3 Financial Instruments (Details) - Level 3 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (13)	$ 3
Total gains — realized/unrealized
Included in earnings	2	7
Included in nuclear decommissioning obligation		4
Purchases	1	4
Transfers into Level 3	4	(8)
Transfers out of Level 3	3	10
Ending balance	(3)	20
Gains/(Losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of June 30, 2017 and 2016	3	(15)
Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	19	17
Total gains — realized/unrealized
Included in earnings	0	1
Included in nuclear decommissioning obligation		0
Purchases	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	19	18
Gains/(Losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of June 30, 2017 and 2016	0	0
Trust Fund Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		54
Total gains — realized/unrealized
Included in earnings		0
Included in nuclear decommissioning obligation		4
Purchases		0
Transfers into Level 3		0
Transfers out of Level 3		0
Ending balance		58
Gains/(Losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of June 30, 2017 and 2016		0
Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(32)	(68)
Total gains — realized/unrealized
Included in earnings	2	6
Included in nuclear decommissioning obligation		0
Purchases	1	4
Transfers into Level 3	4	(8)
Transfers out of Level 3	3	10
Ending balance	(22)	(56)
Gains/(Losses) for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of June 30, 2017 and 2016	$ 3	$ (15)

Fair Value of Financial Instr54

Fair Value of Financial Instruments - Derivative Fair Value Measurements, Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Total derivative assets valued with prices provied by models and other valuation techniques (as a percent)	4.00%
Total derivative liabilities valued with prices provied by models and other valuation techniques (as a percent)	7.00%
Decrease in credit reserve	$ 2,000,000	$ 0

Fair Value of Financial Instr55

Fair Value of Financial Instruments - Derivative Fair Value Measurements (Details) $ in Millions	Mar. 31, 2018USD ($)$ / MWh	Dec. 31, 2017USD ($)$ / MWh
Assets
Derivative assets	$ 1,369	$ 798
Liabilities
Derivative liabilities	1,054	752
Fair value, measurements, recurring
Liabilities
Derivative liabilities	1,054	752
Fair value, measurements, recurring | Level 3
Liabilities
Derivative liabilities	71	77
Commodity contracts
Assets
Derivative assets	1,277	745
Liabilities
Derivative liabilities	1,024	693
Commodity contracts | Fair value, measurements, recurring
Assets
Derivative assets	1,277	745
Liabilities
Derivative liabilities	1,024	693
Commodity contracts | Fair value, measurements, recurring | Level 3
Assets
Derivative assets	49	45
Liabilities
Derivative liabilities	71	77
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts
Assets
Derivative assets	38	34
Liabilities
Derivative liabilities	$ 63	$ 65
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts | Low
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	9	10
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts | High
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	319	142
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts | Weighted Average
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	40	33
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs
Assets
Derivative assets	$ 11	$ 11
Liabilities
Derivative liabilities	$ 8	$ 12
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs | Low
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	(28)	(28)
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs | High
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	46	46
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs | Weighted Average
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	0	0

Fair Value of Financial Instr56

Fair Value of Financial Instruments - Counterparty Credit Risk (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Concentration of Credit Risk
Counterparty credit exposure to a portion of the Company's counterparties	$ 505
Net counterparty credit exposure to a portion of the Company's counterparties	244
Collateral held (cash and letters of credit) against counterparty credit exposure to a portion of the Company's counterparties	$ 264
Company's exposure before collateral is expected to roll off by the end of 2019 (as a percent)	83.00%
Net exposure (as a percent)	100.00%
Counterparty credit risk exposure to certain counterparties, threshold (as a percent)	10.00%
Aggregate counterparty credit risk exposure for counterparties representing exposure above threshold percentage	$ 65
Estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements for the next 5 years	$ 4,100
Period of estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements (in years)	5 years
NRG Yield, Inc.
Concentration of Credit Risk
Estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements for the next 5 years	$ 2,500
Investment grade
Concentration of Credit Risk
Net exposure (as a percent)	78.00%
Non-Investment grade/Non-Rated
Concentration of Credit Risk
Net exposure (as a percent)	22.00%
Utilities, energy merchants, marketers and other
Concentration of Credit Risk
Net exposure (as a percent)	78.00%
Financial institutions
Concentration of Credit Risk
Net exposure (as a percent)	22.00%

Nuclear Decommissioning Trust57

Nuclear Decommissioning Trust Fund - Summary of aggregate fair values and realized gains and losses (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Nuclear decommissioning trust fund
Fair Value	$ 680	$ 692
Unrealized Gains	267	276
Unrealized Losses	6	2
Cash and cash equivalents
Nuclear decommissioning trust fund
Fair Value	16	47
Unrealized Gains	0	0
Unrealized Losses	0	0
U.S. government and federal agency obligations
Nuclear decommissioning trust fund
Fair Value	56	43
Unrealized Gains	1	1
Unrealized Losses	$ 1	$ 0
Weighted-average Maturities (In years)	11 years	11 years
Federal agency mortgage-backed securities
Nuclear decommissioning trust fund
Fair Value	$ 92	$ 82
Unrealized Gains	0	1
Unrealized Losses	$ 2	$ 1
Weighted-average Maturities (In years)	23 years	23 years
Commercial mortgage-backed securities
Nuclear decommissioning trust fund
Fair Value	$ 16	$ 14
Unrealized Gains	0	0
Unrealized Losses	$ 1	$ 0
Weighted-average Maturities (In years)	22 years	20 years
Corporate debt securities
Nuclear decommissioning trust fund
Fair Value	$ 100	$ 99
Unrealized Gains	1	2
Unrealized Losses	$ 2	$ 1
Weighted-average Maturities (In years)	11 years	11 years
Equity securities
Nuclear decommissioning trust fund
Fair Value	$ 395	$ 402
Unrealized Gains	265	272
Unrealized Losses	0	0
Foreign government fixed income securities
Nuclear decommissioning trust fund
Fair Value	5	5
Unrealized Gains	0	0
Unrealized Losses	$ 0	$ 0
Weighted-average Maturities (In years)	8 years	9 years

Nuclear Decommissioning Trust58

Nuclear Decommissioning Trust Fund - Summary of proceeds from sales of available-for-sale securities and related gains and losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Nuclear Decommissioning Trust Fund Disclosure [Abstract]
Realized gains	$ 3	$ 2
Realized losses	3	2
Proceeds from sale of securities	$ 182	$ 117

Accounting for Derivative Ins59

Accounting for Derivative Instruments and Hedging Activities - Net notional volume buy/sell of open derivative transactions (Details) shares in Millions, mw_per_day in Millions, T in Millions, MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)MWhMMBTUmw_per_dayTshares	Dec. 31, 2017USD ($)MWhMMBTUmw_per_dayTshares
Long | Emissions
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, mass (ton)	2	1
Long | Coal
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, mass (ton)	17	21
Long | Power
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, energy (in MMBtu and MWh) | MWh	16	14
Long | Interest
Volumetric Underlying Derivative Transactions
Derivative, notional amount (in usd) | $	$ 3,938	$ 3,876
Long | Equity
Volumetric Underlying Derivative Transactions
Derivative, non-monetary notional amount (in shares) | shares	1	1
Short | Natural Gas
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, energy (in MMBtu and MWh) | MMBTU	208	17
Short | Capacity
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, flow rate (in MW/Day) | mw_per_day	(1)	(1)

Accounting for Derivative Ins60

Accounting for Derivative Instruments and Hedging Activities - Fair value within the derivative instrument valuation (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Assets	$ 1,369	$ 798
Derivative Liabilities	1,054	752
Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	22	12
Derivative Liabilities	9	16
Designated as Hedging Instrument | Interest rate contracts current
Derivative [Line Items]
Derivative Assets	2	1
Derivative Liabilities	2	5
Designated as Hedging Instrument | Interest rate contracts long-term
Derivative [Line Items]
Derivative Assets	20	11
Derivative Liabilities	7	11
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	1,347	786
Derivative Liabilities	1,045	736
Not Designated as Hedging Instrument | Interest rate contracts current
Derivative [Line Items]
Derivative Assets	13	9
Derivative Liabilities	7	15
Not Designated as Hedging Instrument | Interest rate contracts long-term
Derivative [Line Items]
Derivative Assets	57	32
Derivative Liabilities	14	28
Not Designated as Hedging Instrument | Commodity contracts current
Derivative [Line Items]
Derivative Assets	1,000	616
Derivative Liabilities	781	535
Not Designated as Hedging Instrument | Commodity contracts long-term
Derivative [Line Items]
Derivative Assets	277	129
Derivative Liabilities	$ 243	$ 158

Accounting for Derivative Ins61

Accounting for Derivative Instruments and Hedging Activities - Offsetting of derivatives by counterparty master agreement level and collateral received (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative assets	$ 1,369	$ 798
Cash Collateral (Held) / Posted	(240)	(37)
Gross Amounts of Recognized Derivative Liabilities	(1,054)	(752)
Cash Collateral Posted	211	171
Gross Amounts of Recognized Assets / Liabilities	315	46
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	(81)	62
Net Amount	234	108
Commodity contracts
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative assets	1,277	745
Derivative Instruments	(835)	(578)
Cash Collateral (Held) / Posted	(201)	(11)
Net Amount	241	156
Gross Amounts of Recognized Derivative Liabilities	(1,024)	(693)
Derivative Instruments	835	578
Cash Collateral Posted	120	73
Net Amount	(69)	(42)
Gross Amounts of Recognized Assets / Liabilities	253	52
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	(81)	62
Net Amount	172	114
Interest rate contracts
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative assets	92	53
Derivative Instruments	(4)	(3)
Cash Collateral (Held) / Posted	0	0
Net Amount	88	50
Gross Amounts of Recognized Derivative Liabilities	(30)	(59)
Derivative Instruments	4	3
Cash Collateral Posted	0	0
Net Amount	(26)	(56)
Gross Amounts of Recognized Assets / Liabilities	62	(6)
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	0	0
Net Amount	$ 62	$ (6)

Accounting for Derivative Ins62

Accounting for Derivative Instruments and Hedging Activities - Effect of ASC 815 on accumulated OCI balance attributable to hedge derivatives, net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassified from accumulated OCI to income:
Accumulated other comprehensive income (loss), tax	$ 6	$ 14
Losses expected to be realized from OCI during the next twelve months, tax	2
Interest rate contracts
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax
Accumulated OCI beginning balance	(54)	(66)
Reclassified from accumulated OCI to income:
Due to realization of previously deferred amounts	4	3
Mark-to-market of cash flow hedge accounting contracts	19	2
Accumulated OCI ending balance, net of $6, and $14 tax	(31)	(61)
Losses expected to be realized from OCI during the next 12 months, net of $2 tax	$ (9)

Accounting for Derivative Ins63

Accounting for Derivative Instruments and Hedging Activities - Pre-tax effects of economic hedges not designated a cash flow hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Unrealized mark-to-market results
Reversal of previously recognized unrealized losses on settled positions related to economic hedges	$ 2	$ 3
Net unrealized gains/(losses) on open positions related to economic hedges	194	(22)
Total unrealized mark-to-market gains/(losses) for economic hedging activities	196	(19)
Reversal of previously recognized unrealized gains on settled positions related to trading activity	(3)	(15)
Net unrealized gains on open positions related to trading activity	11	1
Total unrealized mark-to-market gains/(losses) for trading activity	8	(14)
Total unrealized losses	204	(33)
Credit Risk Related Contingent Features
Unrealized gain (loss) from open economic hedge positions	194	(22)
Collateral due on net liability position that has not been called by a certain marginable agreement counterparty	5
Adequate Assurance Clauses
Credit Risk Related Contingent Features
Derivative net liability position, collateral required Contracts with Credit Rating Contingent Feature	20
Credit Rating Contingent Features
Credit Risk Related Contingent Features
Derivative net liability position, collateral required Contracts with Credit Rating Contingent Feature	5
Commodity contracts
Unrealized mark-to-market results
Total unrealized losses	204	(33)
Commodity contracts | Sales
Unrealized mark-to-market results
Total unrealized losses	(98)	104
Commodity contracts | Cost of Sales
Unrealized mark-to-market results
Total unrealized losses	302	(137)
Interest rate contracts
Unrealized mark-to-market results
Total unrealized losses	$ 48	$ 5

Debt and Capital Leases - Sched

Debt and Capital Leases - Schedule of Long-term Debt and Capital Leases (Details) - USD ($) $ in Millions	Mar. 21, 2018	Mar. 31, 2018	Dec. 31, 2017	May 26, 2017	Feb. 17, 2017
Debt Instrument [Line Items]
Long-term debt		$ 16,584	$ 16,633
Capital leases		4	5
Subtotal long-term debt and capital leases (including current maturities)		16,588	16,638
Current portion of long-term debt and capital leases		(956)	(688)
Less debt issuance costs		(201)	(204)
Discounts		(25)	(30)
Long-term debt and capital leases		$ 15,406	15,716
Alta Wind I - V lease financing arrangements, due 2034 and 2035 | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		5.696%
Alta Wind I - V lease financing arrangements, due 2034 and 2035 | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		7.015%
Recourse Debt
Debt Instrument [Line Items]
Long-term debt		$ 7,177	7,182
Recourse Debt | Senior notes, due 2022
Debt Instrument [Line Items]
Long-term debt		$ 992	992
Interest rate, stated percentage		6.25%
Recourse Debt | Senior notes, due 2024
Debt Instrument [Line Items]
Long-term debt		$ 733	733
Interest rate, stated percentage		6.25%
Recourse Debt | Senior notes, due 2026
Debt Instrument [Line Items]
Long-term debt		$ 1,000	1,000
Interest rate, stated percentage		7.25%
Recourse Debt | Senior notes, due 2027
Debt Instrument [Line Items]
Long-term debt		$ 1,250	1,250
Interest rate, stated percentage		6.625%
Recourse Debt | Senior notes, due 2028
Debt Instrument [Line Items]
Long-term debt		$ 870	870
Interest rate, stated percentage		5.75%
Recourse Debt | Term loan facility, due 2023
Debt Instrument [Line Items]
Long-term debt		$ 1,867	1,872
Recourse Debt | Term loan facility, due 2023 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%	1.75%
Recourse Debt | Tax-exempt bonds
Debt Instrument [Line Items]
Long-term debt		$ 465	465
Recourse Debt | Tax-exempt bonds | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		4.125%
Recourse Debt | Tax-exempt bonds | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		6.00%
Non Recourse Debt
Debt Instrument [Line Items]
Long-term debt		$ 9,407	9,451
Non Recourse Debt | NRG Yield, Inc. Convertible Senior Notes, due 2019
Debt Instrument [Line Items]
Long-term debt		$ 345	345
Interest rate, stated percentage		3.50%
Non Recourse Debt | NRG Yield, Inc. Convertible Senior Notes, due 2020
Debt Instrument [Line Items]
Long-term debt		$ 288	288
Interest rate, stated percentage		3.25%
Non Recourse Debt | NRG Yield, Inc. Convertible Senior Notes, due 2019
Debt Instrument [Line Items]
Long-term debt		$ 500	500
Interest rate, stated percentage		5.375%
Non Recourse Debt | NRG Yield, Inc. Convertible Senior Notes, due 2020
Debt Instrument [Line Items]
Long-term debt		$ 350	350
Interest rate, stated percentage		5.00%
Non Recourse Debt | NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2019
Debt Instrument [Line Items]
Long-term debt		$ 75	55
Non Recourse Debt | NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2019 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		2.50%
Non Recourse Debt | El Segundo Energy Center, due 2023
Debt Instrument [Line Items]
Long-term debt		$ 369	400
Non Recourse Debt | El Segundo Energy Center, due 2023 | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		1.75%
Non Recourse Debt | El Segundo Energy Center, due 2023 | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		2.375%
Non Recourse Debt | Marsh Landing, due 2023
Debt Instrument [Line Items]
Long-term debt		$ 309	318
Non Recourse Debt | Marsh Landing, due 2023 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		2.125%
Non Recourse Debt | Alta Wind I - V lease financing arrangements, due 2034 and 2035
Debt Instrument [Line Items]
Long-term debt		$ 926	926
Non Recourse Debt | Walnut Creek, term loans due 2023
Debt Instrument [Line Items]
Long-term debt		$ 259	267
Non Recourse Debt | Walnut Creek, term loans due 2023 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.625%
Non Recourse Debt | Utah Portfolio, due 2022
Debt Instrument [Line Items]
Long-term debt		$ 278	278
Non Recourse Debt | Tapestry, due 2021
Debt Instrument [Line Items]
Long-term debt		$ 158	162
Non Recourse Debt | Tapestry, due 2021 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.625%
Non Recourse Debt | CVSR, due 2037
Debt Instrument [Line Items]
Long-term debt		$ 731	746
Non Recourse Debt | CVSR, due 2037 | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		2.339%
Non Recourse Debt | CVSR, due 2037 | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		3.775%
Non Recourse Debt | CVSR HoldCo, due 2037
Debt Instrument [Line Items]
Long-term debt		$ 188	194
Interest rate, stated percentage		4.68%
Non Recourse Debt | Alpine, due 2022
Debt Instrument [Line Items]
Long-term debt		$ 135	135
Non Recourse Debt | Alpine, due 2022 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.75%
Non Recourse Debt | Energy Center Minneapolis, due 2025
Debt Instrument [Line Items]
Long-term debt		$ 83	83
Interest rate, stated percentage		595.00%
Non Recourse Debt | Energy Center Minneapolis, due 2025 | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		3.55%
Non Recourse Debt | Energy Center Minneapolis, due 2025 | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		5.95%
Non Recourse Debt | Energy Center Minneapolis, due 2031
Debt Instrument [Line Items]
Long-term debt		$ 125	125
Interest rate, stated percentage		3.55%
Non Recourse Debt | Viento, due 2023
Debt Instrument [Line Items]
Long-term debt		$ 163	163
Non Recourse Debt | Viento, due 2023 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		3.00%
Non Recourse Debt | Buckthorn Solar, due 2018 and 2025
Debt Instrument [Line Items]
Long-term debt		$ 183	169
Non Recourse Debt | Buckthorn Solar, due 2018 and 2025 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.75%
Non Recourse Debt | NRG Yield - other
Debt Instrument [Line Items]
Long-term debt		$ 573	579
Non Recourse Debt | Subtotal NRG Yield debt (non-recourse to NRG)
Debt Instrument [Line Items]
Long-term debt		6,038	6,083
Non Recourse Debt | Ivanpah, due 2033 and 2038
Debt Instrument [Line Items]
Long-term debt		$ 1,068	1,073
Non Recourse Debt | Ivanpah, due 2033 and 2038 | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		2.285%
Non Recourse Debt | Ivanpah, due 2033 and 2038 | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		4.256%
Non Recourse Debt | Carlsbad Energy Project
Debt Instrument [Line Items]
Long-term debt		$ 475	427
Interest rate, stated percentage				4.12%
Non Recourse Debt | Carlsbad Energy Project | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		1.625%
Non Recourse Debt | Carlsbad Energy Project | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		4.12%
Non Recourse Debt | Agua Caliente, due 2037
Debt Instrument [Line Items]
Long-term debt		$ 815	818
Non Recourse Debt | Agua Caliente, due 2037 | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		2.395%
Non Recourse Debt | Agua Caliente, due 2037 | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		3.633%
Non Recourse Debt | Agua Caliente Borrower 1, due 2038
Debt Instrument [Line Items]
Long-term debt		$ 86	89
Interest rate, stated percentage		5.43%			5.43%
Non Recourse Debt | Cedro Hill, due 2025
Debt Instrument [Line Items]
Long-term debt		$ 149	151
Non Recourse Debt | Cedro Hill, due 2025 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		1.75%
Non Recourse Debt | Midwest Generation, due 2019
Debt Instrument [Line Items]
Long-term debt		$ 132	152
Interest rate, stated percentage		4.39%
Non Recourse Debt | Other Renewables Debt
Debt Instrument [Line Items]
Long-term debt		$ 466	478
Non Recourse Debt | NRG Other
Debt Instrument [Line Items]
Long-term debt		178	180
Non Recourse Debt | Subtotal other NRG non-recourse debt
Debt Instrument [Line Items]
Long-term debt		$ 3,369	$ 3,368

Debt and Capital Leases - Narra

Debt and Capital Leases - Narrative (Details) - USD ($)	Mar. 21, 2018	May 26, 2017	Feb. 17, 2017	Mar. 31, 2018	Apr. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt				$ 16,584,000,000		$ 16,633,000,000
Recourse Debt
Debt Instrument [Line Items]
Long-term debt				7,177,000,000		7,182,000,000
Non Recourse Debt
Debt Instrument [Line Items]
Long-term debt				9,407,000,000		9,451,000,000
Revolving Credit Facility | Carlsbad Financing Agreement
Debt Instrument [Line Items]
Long-term construction loan		$ 194,000,000
Revolving Credit Facility | Letter of Credit
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		83,000,000
Revolving Credit Facility | Working Capital Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity		$ 4,000,000
Term loan facility, due 2023 | Recourse Debt
Debt Instrument [Line Items]
Long-term debt				$ 1,867,000,000		1,872,000,000
Term loan facility, due 2023 | Recourse Debt | LIBOR
Debt Instrument [Line Items]
Change in interest rate	0.50%
Basis spread on variable rate	1.75%			1.75%
Term loan facility, due 2023 | Recourse Debt | LIBOR floor
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
NRG Yield Revolving Credit Facility
Debt Instrument [Line Items]
Borrowing outstanding under revolver				$ 75,000,000
NRG Yield Revolving Credit Facility | Letter of Credit
Debt Instrument [Line Items]
Letters of credit outstanding under revolver				$ 67,000,000
NRG Yield Revolving Credit Facility | Non Recourse Debt
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount				2.50%
Agua Caliente Borrower 1, due 2038 | Non Recourse Debt
Debt Instrument [Line Items]
Percentage of ownership			51.00%
Proceeds from issuance of senior secured debt			$ 130,000,000
Interest rate, stated percentage			5.43%	5.43%
Long-term debt				$ 86,000,000		89,000,000
Carlsbad Energy Project | Non Recourse Debt
Debt Instrument [Line Items]
Interest rate, stated percentage		4.12%
Proceeds from issuance of debt		$ 407,000,000
Long-term debt				475,000,000		$ 427,000,000
Carlsbad Energy Project | Notes Payable
Debt Instrument [Line Items]
Long-term debt				$ 475,000,000
Subsequent Event | NRG Yield Revolving Credit Facility | Non Recourse Debt
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount					1.75%

Variable Interest Entities, o66

Variable Interest Entities, or VIEs (Details) $ in Millions	Nov. 02, 2016	Mar. 31, 2018USD ($)facilityMW	Dec. 31, 2017USD ($)
Investments Accounted for by the Equity Method
Equity investments in affiliates		$ 1,011	$ 1,038
Generation capacity (in MW) | MW		30,000
Deficit restoration obligation		$ 81
Current assets		171	118
Net property, plant and equipment		2,712	2,337
Other long-term assets		665	658
Total assets		3,548	3,113
Current liabilities		111	96
Long-term debt		856	661
Other long-term liabilities		211	209
Total liabilities		1,178	966
Redeemable noncontrolling interest		80	78
Noncontrolling interests		646	507
Net assets less noncontrolling interests		1,644	$ 1,562
GenConn Energy LLC
Investments Accounted for by the Equity Method
Equity investments in affiliates		$ 100
Power generation facilities | facility		2
Generation capacity (in MW) | MW		190
Economic interest in equity method investments (as a percent)		50.00%
Sun Edison Utility-Scale Solar and Wind | Mechanically-complete Solar Assets
Investments Accounted for by the Equity Method
PPA period	20 years
Equity investments in affiliates		$ 338

Changes in Capital Structure -

Changes in Capital Structure - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2018	Feb. 28, 2018	Dec. 31, 2017
Capital Structure
Common stock, shares authorized (in shares)		500,000,000	500,000,000		500,000,000
Shares issued under ESPP (in shares)	175,862
Stock repurchase program, amount, beginning immediately				$ 500
Total number of shares purchased			3,114,748
Commissions per share (in dollars per share)		$ 0.0001
Capital Allocation Plan
Capital Structure
Stock repurchase program, authorized amount				$ 1,000
Total number of shares purchased		3,114,748
Average price paid per share (in dollars per share)		$ 29.75
Amounts paid for shares purchased		$ 93

Changes in Capital Structure 68

Changes in Capital Structure - Changes in NRG's common shares outstanding and issued (Details) - shares	Jan. 01, 2018	Mar. 31, 2018
Schedule of Stock by Class, Equity [Roll Forward]
Balance as of beginning of period (in shares)	418,323,134	418,323,134
Treasury shares, balance as of beginning of period (in shares)	(101,580,045)	(101,580,045)
Outstanding, as of beginning of period (in shares)	316,743,089	316,743,089
Shares issued under LTIPs		1,081,994
Shares issued under ESPP	175,862
Shares repurchased		(3,114,748)
Balance as of end of period (in shares)		419,405,128
Treasury shares, balance as of end of the period (in shares)		(104,518,931)
Outstanding, as of end of period (in shares)		314,886,197
Issued
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs		1,081,994
Shares issued under ESPP	0
Shares repurchased		0
Treasury
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs		0
Shares issued under ESPP	175,862
Shares repurchased		(3,114,748)

Changes in Capital Structure 69

Changes in Capital Structure - Schedule of dividends paid (Details) - $ / shares	Apr. 19, 2018	Mar. 31, 2018	Mar. 31, 2017
Dividends [Abstract]
Dividends Per Common Share (in usd per share)		$ 0.03	$ 0.03
Subsequent Event
Subsequent Event [Line Items]
Common stock dividends declared (in usd per share)	$ 0.03
Common stock dividends proposed annual amount (in usd per share)	$ 0.12

Segment Reporting (Details)

Segment Reporting (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)MW	Mar. 31, 2017USD ($)	Mar. 30, 2018MW	Dec. 31, 2017USD ($)MW
Segment Reporting Information
Generation capacity (in MW) | MW	30,000
Operating revenues	$ 2,421	$ 2,382
Depreciation and amortization	235	257
Reorganization costs	20	0
Equity in earnings/(losses) of unconsolidated affiliates	(2)	5
Income/(loss) from continuing operations before income taxes	232	(173)
Income/(loss) from continuing operations	233	(169)
Loss from discontinued operations, net of income tax	0	(34)
Net Income/(Loss)	233	(203)
Net income/(loss) attributable to NRG Energy, Inc.	279	(163)
Total assets	23,752			$ 23,318
Includes other income - affiliate	0	48
Eliminations
Segment Reporting Information
Operating revenues	300	(244)
Depreciation and amortization	0	0
Reorganization costs	0
Equity in earnings/(losses) of unconsolidated affiliates	(7)	(4)
Income/(loss) from continuing operations before income taxes	(11)	(4)
Income/(loss) from continuing operations	(11)	(4)
Loss from discontinued operations, net of income tax		0
Net Income/(Loss)	(11)	(4)
Net income/(loss) attributable to NRG Energy, Inc.	1	(7)
Total assets	(9,743)
Retail | Operating Segments
Segment Reporting Information
Operating revenues	1,481	1,335
Depreciation and amortization	28	28
Reorganization costs	3
Equity in earnings/(losses) of unconsolidated affiliates	0	0
Income/(loss) from continuing operations before income taxes	946	(31)
Income/(loss) from continuing operations	946	(34)
Loss from discontinued operations, net of income tax		0
Net Income/(Loss)	946	(34)
Net income/(loss) attributable to NRG Energy, Inc.	940	(33)
Total assets	3,521
Includes other income - affiliate		0
Retail | Eliminations
Segment Reporting Information
Operating revenues	(1)	(1)
Generation | Operating Segments
Segment Reporting Information
Operating revenues	327	965
Depreciation and amortization	67	97
Reorganization costs	4
Equity in earnings/(losses) of unconsolidated affiliates	2	(13)
Income/(loss) from continuing operations before income taxes	(536)	37
Income/(loss) from continuing operations	(536)	37
Loss from discontinued operations, net of income tax		0
Net Income/(Loss)	(536)	37
Net income/(loss) attributable to NRG Energy, Inc.	(536)	37
Total assets	7,313
Includes other income - affiliate		0
Generation | Eliminations
Segment Reporting Information
Operating revenues	307	(209)
Renewables | Operating Segments
Segment Reporting Information
Operating revenues	86	95
Depreciation and amortization	51	47
Reorganization costs	0
Equity in earnings/(losses) of unconsolidated affiliates	0	0
Income/(loss) from continuing operations before income taxes	(40)	(35)
Income/(loss) from continuing operations	(34)	(29)
Loss from discontinued operations, net of income tax		0
Net Income/(Loss)	(34)	(29)
Net income/(loss) attributable to NRG Energy, Inc.	1	(1)
Total assets	5,191
Includes other income - affiliate		0
Renewables | Eliminations
Segment Reporting Information
Operating revenues	(8)	(8)
NRG Yield | Operating Segments
Segment Reporting Information
Operating revenues	225	221
Depreciation and amortization	81	77
Reorganization costs	0
Equity in earnings/(losses) of unconsolidated affiliates	4	19
Income/(loss) from continuing operations before income taxes	(1)	(3)
Income/(loss) from continuing operations	0	(2)
Loss from discontinued operations, net of income tax		0
Net Income/(Loss)	0	(2)
Net income/(loss) attributable to NRG Energy, Inc.	21	12
Total assets	8,362
Includes other income - affiliate		0
NRG Yield | Eliminations
Segment Reporting Information
Operating revenues	0	0
Corporate | Operating Segments
Segment Reporting Information
Operating revenues	2	10
Depreciation and amortization	8	8
Reorganization costs	13
Equity in earnings/(losses) of unconsolidated affiliates	(1)	3
Income/(loss) from continuing operations before income taxes	(126)	(137)
Income/(loss) from continuing operations	(132)	(137)
Loss from discontinued operations, net of income tax		(34)
Net Income/(Loss)	(132)	(171)
Net income/(loss) attributable to NRG Energy, Inc.	(148)	(171)
Total assets	9,108
Includes other income - affiliate		48
Corporate | Eliminations
Segment Reporting Information
Operating revenues	$ 2	$ (26)
Buckthorn Renewables, LLC
Segment Reporting Information
Generation capacity (in MW) | MW			154
Discontinued Operations, Held-for-sale or Disposed of by Sale | Buckthorn Renewables, LLC
Segment Reporting Information
Percentage of ownership sold			100.00%
NRG Yield
Segment Reporting Information
Generation capacity (in MW) | MW				555

Earnings_(Loss) Per Share - Rec

Earnings/(Loss) Per Share - Reconciliation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic earnings per share attributable to NRG common stockholders
Net income/(loss) attributable to NRG Energy, Inc.	$ 279	$ (163)
Weighted average number of common shares outstanding — basic (in shares)	318	316
Earnings/(Loss) per Weighted Average Common Share — Basic (in usd per share)	$ 0.88	$ (0.52)
Earnings Per Share, Diluted [Abstract]
Weighted average number of common shares outstanding - diluted (in shares)	318	316
Incremental shares attributable to the issuance of equity compensation (treasury stock method) (in shares)	4	0
Total dilutive shares (in shares)	322	316
Earnings/(loss) per weighted average common share — diluted (in usd per share)	$ 0.87	$ (0.52)

Earnings_(Loss) Per Share - Ant

Earnings/(Loss) Per Share - Anti-dilutive Securities (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	1	6
Equity compensation plans
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	1	6

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Effective Tax Rate
Income/(Loss) before income taxes	$ 232	$ (173)
Income tax benefit	$ (1)	$ (4)
Effective tax rate	(0.40%)	2.30%
Uncertain Tax Benefits
Non-current tax liability for uncertain tax benefits	$ 35
Unrecognized tax benefits, penalties and interest accrued	$ 3

Related Party Transactions - Se

Related Party Transactions - Service Agreement and Transition Services Agreement with GenOn (Details) - USD ($) $ in Millions	Jun. 12, 2017	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Notice of termination, period		60 days
Other income - affiliate			$ 0	$ 48
Services Agreement | Restructuring Support Agreement
Related Party Transaction [Line Items]
Shared services, annualized rate		$ 84			$ 84
Credit applied					28
GenOn | Services Agreement
Related Party Transaction [Line Items]
Service fees			193
Shared services, annualized rate		$ 84			$ 84
Credit applied	$ 28
GenOn | Transition Services Agreement | Restructuring Support Agreement
Related Party Transaction [Line Items]
Selling, general and administrative expenses			$ 21

Related Party Transactions - Cr

Related Party Transactions - Credit Agreement with GenOn (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Long-term debt	$ 16,584,000,000	$ 16,633,000,000
Cash collateral paid in support of energy risk management activities	211,000,000	171,000,000
GenOn
Related Party Transaction [Line Items]
Cash collateral paid in support of energy risk management activities	28,000,000	32,000,000
Settlement consideration	261,300,000
GenOn | Revolving Credit Facility | Intercompany Credit Agreement
Related Party Transaction [Line Items]
Credit facility maximum borrowing capacity	500,000,000
Letters of credit outstanding under revolver	86,000,000	$ 92,000,000
Long-term debt	$ 125,000,000

Commitments and Contingencies (

Commitments and Contingencies (Details)

Mar. 27, 2018USD ($)

Feb. 16, 2018USD ($)

Nov. 07, 2017USD ($)

Sep. 07, 2017USD ($)

Jun. 01, 2001

Mar. 31, 2018USD ($)

May 31, 2016case

Jun. 30, 2013case

Jun. 30, 2010ClaimPlaintiff

Aug. 31, 2009generatingunit

Mar. 31, 2018USD ($)lawsuit

Mar. 10, 2010Claim

Jul. 31, 2013Claim

Mar. 31, 2018Plaintiff

Dec. 13, 2016

Dec. 31, 2012Claim

Sep. 30, 2012Claim

GenOn Energy | Senior Notes | Senior Unsecured Notes 2017

Loss Contingencies

Interest rate, stated percentage

7.875%

GenOn Energy | Senior Notes | Senior Unsecured Notes 2018

Loss Contingencies

Interest rate, stated percentage

9.50%

GenOn Energy | Senior Notes | Senior Unsecured Notes 2020

Loss Contingencies

Interest rate, stated percentage

9.875%

GenOn Americas Generation, LLC | Senior Notes | Senior Unsecured Notes 2021

Loss Contingencies

Interest rate, stated percentage

8.50%

GenOn Americas Generation, LLC | Senior Notes | Senior Unsecured Notes 2031

Loss Contingencies

Interest rate, stated percentage

9.125%

Midwest Generation Asbestos Liabilities

Loss Contingencies

Damages sought, amount

$ 61,000,000

Telephone Consumer Protection Act Purported Class Actions

Loss Contingencies

Damages sought, amount

$ 1,500

Number of lawsuits/cases | lawsuit

3

Telephone Consumer Protection Act Purported Class Actions | CALIFORNIA

Loss Contingencies

Number of lawsuits/cases | lawsuit

1

Telephone Consumer Protection Act Purported Class Actions | NEW JERSEY

Loss Contingencies

Number of lawsuits/cases | lawsuit

2

CDWR and SDGE v Sunrise Power

Loss Contingencies

Damages sought, amount

$ 1,200,000

PPA period

10 years

Remaining term

70 months

Morgantown V. GenOn Mid-Atlantic

Loss Contingencies

Damages sought, amount

$ 0

BTEC New Albany v. NRG Texas Power LLC

Loss Contingencies

Damages sought, amount

$ 48,000,000

Natural Gas Litigation

Loss Contingencies

Motion filed to dismiss, claims number | case

1

Pending claims | Claim

5

Number of lawsuits/cases | case

1

Natixis V. GenOn Mid-Atlantic

Loss Contingencies

Damages sought, amount

$ 34,000,000

Midwest Generation New Source Review

Loss Contingencies

Number of coal-fired electric generating stations | generatingunit

6

Motion filed to dismiss, claims number | Claim

9

9

Pending claims | Claim

10

10

1

Plaintiffs | Plaintiff

1

1

Midwest Generation New Source Review | State of Illinois

Loss Contingencies

Settlement amount to be paid

$ 500,000

Midwest Generation New Source Review | Federal Government

Loss Contingencies

Settlement amount to be paid

$ 500,000

Minimum | Midwest Generation New Source Review

Loss Contingencies

Pending claims | Plaintiff

1

Maximum | Midwest Generation New Source Review

Loss Contingencies

Pending claims | Claim

10

Regulatory Matters (Details)

Regulatory Matters (Details) $ in Millions	Dec. 20, 2013USD ($)
GenOn
Regulatory Assets [Line Items]
Regulatory payments sought	$ 22

Condensed Consolidating Finan78

Condensed Consolidating Financial Information - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt	$ 16,584	$ 16,633
Recourse Debt
Debt Instrument [Line Items]
Long-term debt	7,177	$ 7,182
Senior Notes | Recourse Debt
Debt Instrument [Line Items]
Long-term debt	$ 4,800

Condensed Consolidating Finan79

Condensed Consolidating Financial Information - STATEMENTS OF OPERATIONS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Revenues
Total operating revenues	$ 2,421	$ 2,382
Operating Costs and Expenses
Cost of operations	1,558	1,862
Depreciation and amortization	235	257
Selling, general and administrative	191	260
Reorganization costs	20	0
Development costs	13	17
Total operating costs and expenses	2,017	2,396
Other income - affiliate	0	48
Gain on sale of assets	2	2
Operating Income/(Loss)	406	36
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	0	0
Equity in (losses)/earnings of unconsolidated affiliates	(2)	5
Other income/(expense), net	(3)	13
Loss on debt extinguishment, net	(2)	(2)
Interest expense	(167)	(225)
Total other expense	(174)	(209)
Income/(Loss) from Continuing Operations Before Income Taxes	232	(173)
Income tax expense/(benefit)	(1)	(4)
Income/(Loss) from Continuing Operations	233	(169)
Loss from discontinued operations, net of income tax	0	(34)
Net Income/(Loss)	233	(203)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	(46)	(40)
Net Income Attributable to NRG Energy, Inc.	279	(163)
Eliminations
Operating Revenues
Total operating revenues	53	(84)
Operating Costs and Expenses
Cost of operations	53	(80)
Depreciation and amortization	0	0
Selling, general and administrative	0	0
Reorganization costs	0
Development costs	0	0
Total operating costs and expenses	53	(80)
Other income - affiliate		0
Gain on sale of assets	0	0
Operating Income/(Loss)	0	(4)
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	(540)	(27)
Equity in (losses)/earnings of unconsolidated affiliates	0	0
Other income/(expense), net	(16)	3
Loss on debt extinguishment, net	0	0
Interest expense		0
Total other expense	(556)	(24)
Income/(Loss) from Continuing Operations Before Income Taxes	(556)	(28)
Income tax expense/(benefit)	0	(2)
Income/(Loss) from Continuing Operations		(26)
Loss from discontinued operations, net of income tax		0
Net Income/(Loss)	(556)	(26)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	(16)	1
Net Income Attributable to NRG Energy, Inc.	(540)	(27)
Guarantor Subsidiaries
Operating Revenues
Total operating revenues	1,483	1,599
Operating Costs and Expenses
Cost of operations	1,082	1,260
Depreciation and amortization	73	99
Selling, general and administrative	98	96
Reorganization costs	2
Development costs	0	0
Total operating costs and expenses	1,255	1,455
Other income - affiliate		0
Gain on sale of assets	3	2
Operating Income/(Loss)	231	146
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	210	(42)
Equity in (losses)/earnings of unconsolidated affiliates	0	(1)
Other income/(expense), net	21	(2)
Loss on debt extinguishment, net	0	0
Interest expense	(3)	(4)
Total other expense	228	(49)
Income/(Loss) from Continuing Operations Before Income Taxes	459	97
Income tax expense/(benefit)	113	19
Income/(Loss) from Continuing Operations		78
Loss from discontinued operations, net of income tax		0
Net Income/(Loss)	346	78
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	0	0
Net Income Attributable to NRG Energy, Inc.	346	78
Non-Guarantor Subsidiaries
Operating Revenues
Total operating revenues	885	867
Operating Costs and Expenses
Cost of operations	409	664
Depreciation and amortization	154	150
Selling, general and administrative	32	46
Reorganization costs	0
Development costs	9	12
Total operating costs and expenses	604	872
Other income - affiliate		0
Gain on sale of assets	(1)	0
Operating Income/(Loss)	280	(5)
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	0	1
Equity in (losses)/earnings of unconsolidated affiliates	(1)	7
Other income/(expense), net	(11)	5
Loss on debt extinguishment, net	0	(2)
Interest expense	(72)	(104)
Total other expense	(84)	(93)
Income/(Loss) from Continuing Operations Before Income Taxes	196	(98)
Income tax expense/(benefit)	48	(46)
Income/(Loss) from Continuing Operations		(52)
Loss from discontinued operations, net of income tax		(37)
Net Income/(Loss)	148	(89)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	(46)	(38)
Net Income Attributable to NRG Energy, Inc.	194	(51)
NRG Energy, Inc. (Note Issuer)
Operating Revenues
Total operating revenues	0	0
Operating Costs and Expenses
Cost of operations	14	18
Depreciation and amortization	8	8
Selling, general and administrative	61	118
Reorganization costs	18
Development costs	4	5
Total operating costs and expenses	105	149
Other income - affiliate		48
Gain on sale of assets	0	0
Operating Income/(Loss)	(105)	(101)
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	330	68
Equity in (losses)/earnings of unconsolidated affiliates	(1)	(1)
Other income/(expense), net	3	7
Loss on debt extinguishment, net	(2)	0
Interest expense	(92)	(117)
Total other expense	238	(43)
Income/(Loss) from Continuing Operations Before Income Taxes	133	(144)
Income tax expense/(benefit)	(162)	25
Income/(Loss) from Continuing Operations		(169)
Loss from discontinued operations, net of income tax		3
Net Income/(Loss)	295	(166)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	16	(3)
Net Income Attributable to NRG Energy, Inc.	$ 279	$ (163)

Condensed Consolidating Finan80

Condensed Consolidating Financial Information - COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Net Income	$ 233	$ (203)
Other Comprehensive (Loss)/Income, net of tax
Unrealized gain on derivatives, net	14	4
Foreign currency translation adjustments, net	(2)	7
Defined benefit plans, net	(1)	0
Other comprehensive income	11	11
Comprehensive Income/(Loss)	244	(192)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	(38)	(39)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	282	(153)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net Income	(556)	(26)
Other Comprehensive (Loss)/Income, net of tax
Unrealized gain on derivatives, net	(17)	(5)
Foreign currency translation adjustments, net	5	(9)
Defined benefit plans, net	0	0
Other comprehensive income	(12)	(14)
Comprehensive Income/(Loss)	(568)	(40)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	(16)	1
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	(552)	(41)
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Income	346	78
Other Comprehensive (Loss)/Income, net of tax
Unrealized gain on derivatives, net	0	0
Foreign currency translation adjustments, net	(2)	5
Defined benefit plans, net	0	0
Other comprehensive income	(2)	5
Comprehensive Income/(Loss)	344	83
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	0	0
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	344	83
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Income	148	(89)
Other Comprehensive (Loss)/Income, net of tax
Unrealized gain on derivatives, net	16	5
Foreign currency translation adjustments, net	(2)	4
Defined benefit plans, net	0	1
Other comprehensive income	14	10
Comprehensive Income/(Loss)	162	(79)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	(46)	(37)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	208	(42)
NRG Energy, Inc. (Note Issuer)
Condensed Financial Statements, Captions [Line Items]
Net Income	295	(166)
Other Comprehensive (Loss)/Income, net of tax
Unrealized gain on derivatives, net	15	4
Foreign currency translation adjustments, net	(3)	7
Defined benefit plans, net	(1)	(1)
Other comprehensive income	11	10
Comprehensive Income/(Loss)	306	(156)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	24	(3)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	$ 282	$ (153)

Condensed Consolidating Finan81

Condensed Consolidating Financial Information - BALANCE SHEETS (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 764	$ 991	$ 627	$ 938
Funds deposited by counterparties	241	37	3	2
Restricted cash	407	508	$ 397	$ 446
Accounts receivable, net	903	1,079
Inventory	528	532
Derivative instruments	1,015	626
Cash collateral paid in support of energy risk management activities	211	171
Accounts receivable - affiliate	73	95
Prepayments and other current assets	326	261
Current assets held-for-sale	89	115
Total current assets	4,557	4,415
Property, plant and equipment, net	13,911	13,908
Other Assets
Investment in subsidiaries	0	0
Equity investments in affiliates	1,011	1,038
Goodwill	539	539
Intangible assets, net	1,726	1,746
Nuclear decommissioning trust fund	680	692
Derivative instruments	354	172
Deferred income tax	136	134
Non-current assets held-for-sale	157	43
Other non-current assets	681	631
Total other assets	5,284	4,995
Total Assets	23,752	23,318
Current Liabilities
Current portion of long-term debt and capital leases	956	688
Accounts payable	787	881
Accounts payable - affiliate	32	33
Derivative instruments	790	555
Cash collateral received in support of energy risk management activities	240	37
Current liabilities held-for-sale	80	72
Accrued expenses and other current liabilities	662	890
Accrued expenses and other current liabilities-affiliate	161	161
Total current liabilities	3,708	3,317
Other Liabilities
Long-term debt and capital leases	15,406	15,716
Nuclear decommissioning reserve	272	269
Nuclear decommissioning trust liability	400	415
Deferred income taxes	20	21
Derivative instruments	264	197
Out-of-market contracts, net	201	207
Non-current liabilities held-for-sale	7	8
Other non-current liabilities	1,136	1,122
Total non-current liabilities	17,706	17,955
Total Liabilities	21,414	21,272
Redeemable noncontrolling interest in subsidiaries	80	78
Total Stockholders’ Equity	2,258	1,968
Total Liabilities and Stockholders’ Equity	23,752	23,318
Eliminations
Current Assets
Cash and cash equivalents	0	0
Funds deposited by counterparties	0	0
Restricted cash	0	0
Accounts receivable, net	0	0
Inventory	0	0
Derivative instruments	(136)	(89)
Cash collateral paid in support of energy risk management activities	0	0
Accounts receivable - affiliate	(1,068)	(698)
Prepayments and other current assets	0	0
Current assets held-for-sale	0	0
Total current assets	(1,204)	(787)
Property, plant and equipment, net	(25)	(26)
Other Assets
Investment in subsidiaries	(7,886)	(7,886)
Equity investments in affiliates	0	0
Goodwill	0	0
Intangible assets, net	(3)	(3)
Nuclear decommissioning trust fund	0	0
Derivative instruments	(47)	(20)
Deferred income tax	0	0
Non-current assets held-for-sale	0	0
Other non-current assets	0	(38)
Total other assets	(7,936)	(7,947)
Total Assets	(9,165)	(8,760)
Current Liabilities
Current portion of long-term debt and capital leases	0	(38)
Accounts payable	0	0
Accounts payable - affiliate	(1,068)	(698)
Derivative instruments	(136)	(88)
Cash collateral received in support of energy risk management activities	0	0
Current liabilities held-for-sale	0	0
Accrued expenses and other current liabilities	0	0
Accrued expenses and other current liabilities-affiliate	0	0
Total current liabilities	(1,204)	(824)
Other Liabilities
Long-term debt and capital leases	0	0
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Deferred income taxes	0	0
Derivative instruments	(47)	(20)
Out-of-market contracts, net	0	0
Non-current liabilities held-for-sale	0	0
Other non-current liabilities	0	0
Total non-current liabilities	(47)	(20)
Total Liabilities	(1,251)	(844)
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders’ Equity	(7,914)	(7,916)
Total Liabilities and Stockholders’ Equity	(9,165)	(8,760)
Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	43	0
Funds deposited by counterparties	241	37
Restricted cash	8	4
Accounts receivable, net	610	768
Inventory	323	338
Derivative instruments	932	625
Cash collateral paid in support of energy risk management activities	211	170
Accounts receivable - affiliate	509	709
Prepayments and other current assets	154	116
Current assets held-for-sale	0	8
Total current assets	3,031	2,775
Property, plant and equipment, net	2,500	2,502
Other Assets
Investment in subsidiaries	511	305
Equity investments in affiliates	0	0
Goodwill	360	360
Intangible assets, net	439	454
Nuclear decommissioning trust fund	680	692
Derivative instruments	245	121
Deferred income tax	264	377
Non-current assets held-for-sale	0	0
Other non-current assets	73	50
Total other assets	2,572	2,359
Total Assets	8,103	7,636
Current Liabilities
Current portion of long-term debt and capital leases	0	0
Accounts payable	510	545
Accounts payable - affiliate	1,662	751
Derivative instruments	857	535
Cash collateral received in support of energy risk management activities	240	37
Current liabilities held-for-sale	0	0
Accrued expenses and other current liabilities	236	290
Accrued expenses and other current liabilities-affiliate	0	0
Total current liabilities	3,505	2,158
Other Liabilities
Long-term debt and capital leases	244	244
Nuclear decommissioning reserve	272	269
Nuclear decommissioning trust liability	400	415
Deferred income taxes	112	112
Derivative instruments	224	110
Out-of-market contracts, net	62	66
Non-current liabilities held-for-sale	0	0
Other non-current liabilities	419	410
Total non-current liabilities	1,733	1,626
Total Liabilities	5,238	3,784
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders’ Equity	2,865	3,852
Total Liabilities and Stockholders’ Equity	8,103	7,636
Non-Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	371	348
Funds deposited by counterparties	0	0
Restricted cash	399	504
Accounts receivable, net	290	307
Inventory	205	194
Derivative instruments	207	81
Cash collateral paid in support of energy risk management activities	0	1
Accounts receivable - affiliate	141	213
Prepayments and other current assets	134	118
Current assets held-for-sale	89	107
Total current assets	1,836	1,873
Property, plant and equipment, net	11,196	11,194
Other Assets
Investment in subsidiaries	1	0
Equity investments in affiliates	1,010	1,036
Goodwill	179	179
Intangible assets, net	1,290	1,295
Nuclear decommissioning trust fund	0	0
Derivative instruments	118	40
Deferred income tax	(34)	(7)
Non-current assets held-for-sale	157	43
Other non-current assets	489	461
Total other assets	3,210	3,047
Total Assets	16,242	16,114
Current Liabilities
Current portion of long-term debt and capital leases	935	667
Accounts payable	241	281
Accounts payable - affiliate	(121)	(201)
Derivative instruments	69	108
Cash collateral received in support of energy risk management activities	0	0
Current liabilities held-for-sale	80	72
Accrued expenses and other current liabilities	146	175
Accrued expenses and other current liabilities-affiliate	0	0
Total current liabilities	1,350	1,102
Other Liabilities
Long-term debt and capital leases	8,387	8,733
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Deferred income taxes	64	64
Derivative instruments	87	107
Out-of-market contracts, net	139	141
Non-current liabilities held-for-sale	7	8
Other non-current liabilities	324	321
Total non-current liabilities	9,008	9,374
Total Liabilities	10,358	10,476
Redeemable noncontrolling interest in subsidiaries	80	78
Total Stockholders’ Equity	5,804	5,560
Total Liabilities and Stockholders’ Equity	16,242	16,114
NRG Energy, Inc. (Note Issuer)
Current Assets
Cash and cash equivalents	350	643
Funds deposited by counterparties	0	0
Restricted cash	0	0
Accounts receivable, net	3	4
Inventory	0	0
Derivative instruments	12	9
Cash collateral paid in support of energy risk management activities	0	0
Accounts receivable - affiliate	491	(129)
Prepayments and other current assets	38	27
Current assets held-for-sale	0	0
Total current assets	894	554
Property, plant and equipment, net	240	238
Other Assets
Investment in subsidiaries	7,374	7,581
Equity investments in affiliates	1	2
Goodwill	0	0
Intangible assets, net	0	0
Nuclear decommissioning trust fund	0	0
Derivative instruments	38	31
Deferred income tax	(94)	(236)
Non-current assets held-for-sale	0	0
Other non-current assets	119	158
Total other assets	7,438	7,536
Total Assets	8,572	8,328
Current Liabilities
Current portion of long-term debt and capital leases	21	59
Accounts payable	36	55
Accounts payable - affiliate	(441)	181
Derivative instruments	0	0
Cash collateral received in support of energy risk management activities	0	0
Current liabilities held-for-sale	0	0
Accrued expenses and other current liabilities	280	425
Accrued expenses and other current liabilities-affiliate	161	161
Total current liabilities	57	881
Other Liabilities
Long-term debt and capital leases	6,775	6,739
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Deferred income taxes	(156)	(155)
Derivative instruments	0	0
Out-of-market contracts, net	0	0
Non-current liabilities held-for-sale	0	0
Other non-current liabilities	393	391
Total non-current liabilities	7,012	6,975
Total Liabilities	7,069	7,856
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders’ Equity	1,503	472
Total Liabilities and Stockholders’ Equity	$ 8,572	$ 8,328

Condensed Consolidating Finan82

Condensed Consolidating Financial Information - CASH FLOWS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows from Operating Activities
Net Income/(Loss)	$ 233	$ (203)
(Loss)/income from discontinued operations	0	(34)
Net income	233	(169)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates	10	13
Equity in losses of unconsolidated affiliates	2	(5)
Depreciation and amortization	235	257
Provision for bad debts	15	9
Amortization of nuclear fuel	13	12
Amortization of financing costs and debt discount/premiums	14	15
Adjustment for debt extinguishment	2	0
Amortization of intangibles and out-of-market contracts	22	30
Amortization of unearned equity compensation	13	8
Changes in deferred income taxes and liability for uncertain tax benefits	(3)	1
Changes in nuclear decommissioning trust liability	34	36
Changes in derivative instruments	(247)	38
Changes in collateral deposits in support of energy risk management activities	163	(127)
Gain on sale of emission allowances	(8)	0
(Gain)/loss on sale of assets	(2)	(2)
Changes in other working capital	(139)	(198)
Cash provided/(used) by continuing operations	357	(82)
Cash used by discontinued operations	0	15
Net Cash Provided/(Used) by Operating Activities	357	(67)
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.	0	0
Intercompany dividends		0
Acquisition of Drop Down Assets, net of cash acquired	0	0
Acquisitions of businesses, net of cash acquired	(62)	(3)
Capital expenditures	(358)	(236)
Decrease in notes receivable	3	4
Purchases of emission allowances	(17)	(9)
Proceeds from sale of emission allowances	23	11
Investments in nuclear decommissioning trust fund securities	(216)	(153)
Proceeds from the sale of nuclear decommissioning trust fund securities	182	117
Proceeds from sale of assets, net of cash disposed of	11	14
Change in investments in unconsolidated affiliates	2	(12)
Other	0	18
Cash (used)/provided by continuing operations	(432)	(249)
Cash used by discontinued operations	0	(32)
Net Cash (Used)/Provided by Investing Activities	(432)	(281)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.	0	0
Payment from/(for) intercompany loans	0	0
Acquisition of Drop Down Assets, net of cash acquired	0	0
Intercompany dividends		0
Payment of dividends to common and preferred stockholders	(10)	(9)
Payment for treasury stock	(93)	0
Net receipts from settlement of acquired derivatives that include financing elements	0	1
Proceeds from issuance of long-term debt	179	193
Payments for short and long-term debt	(228)	(177)
Distributions to, net of contributions from, noncontrolling interests in subsidiaries	110	(5)
Payment of debt issuance costs	(7)	(14)
Other - contingent consideration	0	(10)
Cash used by continuing operations	(49)	(21)
Cash used by discontinued operations	0	(132)
Net Cash Used by Financing Activities	(49)	(153)
Effect of exchange rate changes on cash and cash equivalents	0	(7)
Change in Cash from discontinued operations	0	(149)
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash	(124)	(359)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period	1,536	1,386
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	1,412	1,027
Eliminations
Cash Flows from Operating Activities
Net Income/(Loss)	(556)	(26)
(Loss)/income from discontinued operations		0
Net income		(26)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates	(3)	(5)
Equity in losses of unconsolidated affiliates	0	0
Depreciation and amortization	0	0
Provision for bad debts	0	0
Amortization of nuclear fuel	0	0
Amortization of financing costs and debt discount/premiums	0	0
Adjustment for debt extinguishment	0
Amortization of intangibles and out-of-market contracts	0	0
Amortization of unearned equity compensation	0	0
Changes in deferred income taxes and liability for uncertain tax benefits	0	0
Changes in nuclear decommissioning trust liability	0	0
Changes in derivative instruments	(18)	0
Changes in collateral deposits in support of energy risk management activities	0	0
Gain on sale of emission allowances	0
(Gain)/loss on sale of assets	0	0
Changes in other working capital	577	63
Cash provided/(used) by continuing operations		32
Cash used by discontinued operations		0
Net Cash Provided/(Used) by Operating Activities	0	32
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.	(25)	(22)
Intercompany dividends		(129)
Acquisition of Drop Down Assets, net of cash acquired	42	131
Acquisitions of businesses, net of cash acquired	0	0
Capital expenditures	0	0
Decrease in notes receivable	0	0
Purchases of emission allowances	0	0
Proceeds from sale of emission allowances	0	0
Investments in nuclear decommissioning trust fund securities	0	0
Proceeds from the sale of nuclear decommissioning trust fund securities	0	0
Proceeds from sale of assets, net of cash disposed of	0	0
Change in investments in unconsolidated affiliates	0	0
Other		0
Cash (used)/provided by continuing operations		(20)
Cash used by discontinued operations		0
Net Cash (Used)/Provided by Investing Activities	17	(20)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.	25	22
Payment from/(for) intercompany loans	0	(32)
Acquisition of Drop Down Assets, net of cash acquired	(42)	(131)
Intercompany dividends		129
Payment of dividends to common and preferred stockholders	0	0
Payment for treasury stock	0
Net receipts from settlement of acquired derivatives that include financing elements		0
Proceeds from issuance of long-term debt	0	0
Payments for short and long-term debt	0	0
Distributions to, net of contributions from, noncontrolling interests in subsidiaries	0	0
Payment of debt issuance costs	0	0
Other - contingent consideration		0
Cash used by continuing operations		(12)
Cash used by discontinued operations		0
Net Cash Used by Financing Activities	(17)	(12)
Effect of exchange rate changes on cash and cash equivalents		0
Change in Cash from discontinued operations		0
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash	0	0
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period	0	0
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	0	0
Guarantor Subsidiaries
Cash Flows from Operating Activities
Net Income/(Loss)	346	78
(Loss)/income from discontinued operations		0
Net income		78
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates	0	0
Equity in losses of unconsolidated affiliates	0	1
Depreciation and amortization	73	99
Provision for bad debts	17	8
Amortization of nuclear fuel	13	12
Amortization of financing costs and debt discount/premiums	0	0
Adjustment for debt extinguishment	0
Amortization of intangibles and out-of-market contracts	3	6
Amortization of unearned equity compensation	0	0
Changes in deferred income taxes and liability for uncertain tax benefits	114	19
Changes in nuclear decommissioning trust liability	34	36
Changes in derivative instruments	5	(4)
Changes in collateral deposits in support of energy risk management activities	162	(136)
Gain on sale of emission allowances	(8)
(Gain)/loss on sale of assets	(3)	(2)
Changes in other working capital	(442)	(118)
Cash provided/(used) by continuing operations		(1)
Cash used by discontinued operations		0
Net Cash Provided/(Used) by Operating Activities	314	(1)
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.	0	0
Intercompany dividends		0
Acquisition of Drop Down Assets, net of cash acquired	0	0
Acquisitions of businesses, net of cash acquired	(2)	0
Capital expenditures	(61)	(64)
Decrease in notes receivable	0	0
Purchases of emission allowances	(17)	(9)
Proceeds from sale of emission allowances	23	11
Investments in nuclear decommissioning trust fund securities	(216)	(153)
Proceeds from the sale of nuclear decommissioning trust fund securities	182	117
Proceeds from sale of assets, net of cash disposed of	10	11
Change in investments in unconsolidated affiliates	0	0
Other		18
Cash (used)/provided by continuing operations		(69)
Cash used by discontinued operations		0
Net Cash (Used)/Provided by Investing Activities	(81)	(69)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.	0	0
Payment from/(for) intercompany loans	18	65
Acquisition of Drop Down Assets, net of cash acquired	0	0
Intercompany dividends		0
Payment of dividends to common and preferred stockholders	0	0
Payment for treasury stock	0
Net receipts from settlement of acquired derivatives that include financing elements		0
Proceeds from issuance of long-term debt	0	0
Payments for short and long-term debt	0	0
Distributions to, net of contributions from, noncontrolling interests in subsidiaries	0	0
Payment of debt issuance costs	0	0
Other - contingent consideration		0
Cash used by continuing operations		65
Cash used by discontinued operations		0
Net Cash Used by Financing Activities	18	65
Effect of exchange rate changes on cash and cash equivalents		0
Change in Cash from discontinued operations		0
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash	251	(5)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period	41	13
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	292	8
Non-Guarantor Subsidiaries
Cash Flows from Operating Activities
Net Income/(Loss)	148	(89)
(Loss)/income from discontinued operations		(37)
Net income		(52)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates	13	18
Equity in losses of unconsolidated affiliates	1	(7)
Depreciation and amortization	154	150
Provision for bad debts	(2)	1
Amortization of nuclear fuel	0	0
Amortization of financing costs and debt discount/premiums	10	11
Adjustment for debt extinguishment	0
Amortization of intangibles and out-of-market contracts	19	24
Amortization of unearned equity compensation	0	0
Changes in deferred income taxes and liability for uncertain tax benefits	27	(46)
Changes in nuclear decommissioning trust liability	0	0
Changes in derivative instruments	(220)	43
Changes in collateral deposits in support of energy risk management activities	1	9
Gain on sale of emission allowances	0
(Gain)/loss on sale of assets	1	0
Changes in other working capital	22	458
Cash provided/(used) by continuing operations		609
Cash used by discontinued operations		15
Net Cash Provided/(Used) by Operating Activities	174	624
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.	0	0
Intercompany dividends		0
Acquisition of Drop Down Assets, net of cash acquired	(42)	(131)
Acquisitions of businesses, net of cash acquired	(60)	(3)
Capital expenditures	(276)	(168)
Decrease in notes receivable	3	4
Purchases of emission allowances	0	0
Proceeds from sale of emission allowances	0	0
Investments in nuclear decommissioning trust fund securities	0	0
Proceeds from the sale of nuclear decommissioning trust fund securities	0	0
Proceeds from sale of assets, net of cash disposed of	1	3
Change in investments in unconsolidated affiliates	2	(12)
Other		0
Cash (used)/provided by continuing operations		(307)
Cash used by discontinued operations		(32)
Net Cash (Used)/Provided by Investing Activities	(372)	(339)
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.	(25)	(22)
Payment from/(for) intercompany loans	80	(428)
Acquisition of Drop Down Assets, net of cash acquired	0	0
Intercompany dividends		(129)
Payment of dividends to common and preferred stockholders	0	0
Payment for treasury stock	0
Net receipts from settlement of acquired derivatives that include financing elements		1
Proceeds from issuance of long-term debt	179	167
Payments for short and long-term debt	(222)	(146)
Distributions to, net of contributions from, noncontrolling interests in subsidiaries	110	(5)
Payment of debt issuance costs	(6)	(10)
Other - contingent consideration		(10)
Cash used by continuing operations		(582)
Cash used by discontinued operations		(132)
Net Cash Used by Financing Activities	116	(714)
Effect of exchange rate changes on cash and cash equivalents		(7)
Change in Cash from discontinued operations		(149)
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash	(82)	(287)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period	852	1,050
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	770	763
NRG Energy, Inc. (Note Issuer)
Cash Flows from Operating Activities
Net Income/(Loss)	295	(166)
(Loss)/income from discontinued operations		3
Net income		(169)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions from unconsolidated affiliates	0	0
Equity in losses of unconsolidated affiliates	1	1
Depreciation and amortization	8	8
Provision for bad debts	0	0
Amortization of nuclear fuel	0	0
Amortization of financing costs and debt discount/premiums	4	4
Adjustment for debt extinguishment	2
Amortization of intangibles and out-of-market contracts	0	0
Amortization of unearned equity compensation	13	8
Changes in deferred income taxes and liability for uncertain tax benefits	(144)	28
Changes in nuclear decommissioning trust liability	0	0
Changes in derivative instruments	(14)	(1)
Changes in collateral deposits in support of energy risk management activities	0	0
Gain on sale of emission allowances	0
(Gain)/loss on sale of assets	0	0
Changes in other working capital	(296)	(601)
Cash provided/(used) by continuing operations		(722)
Cash used by discontinued operations		0
Net Cash Provided/(Used) by Operating Activities	(131)	(722)
Cash Flows from Investing Activities
Dividends from NRG Yield, Inc.	25	22
Intercompany dividends		129
Acquisition of Drop Down Assets, net of cash acquired	0	0
Acquisitions of businesses, net of cash acquired	0	0
Capital expenditures	(21)	(4)
Decrease in notes receivable	0	0
Purchases of emission allowances	0	0
Proceeds from sale of emission allowances	0	0
Investments in nuclear decommissioning trust fund securities	0	0
Proceeds from the sale of nuclear decommissioning trust fund securities	0	0
Proceeds from sale of assets, net of cash disposed of	0	0
Change in investments in unconsolidated affiliates	0	0
Other		0
Cash (used)/provided by continuing operations		147
Cash used by discontinued operations		0
Net Cash (Used)/Provided by Investing Activities	4	147
Cash Flows from Financing Activities
Dividends from NRG Yield, Inc.	0	0
Payment from/(for) intercompany loans	(98)	395
Acquisition of Drop Down Assets, net of cash acquired	42	131
Intercompany dividends		0
Payment of dividends to common and preferred stockholders	(10)	(9)
Payment for treasury stock	(93)
Net receipts from settlement of acquired derivatives that include financing elements		0
Proceeds from issuance of long-term debt	0	26
Payments for short and long-term debt	(6)	(31)
Distributions to, net of contributions from, noncontrolling interests in subsidiaries	0	0
Payment of debt issuance costs	(1)	(4)
Other - contingent consideration		0
Cash used by continuing operations		508
Cash used by discontinued operations		0
Net Cash Used by Financing Activities	(166)	508
Effect of exchange rate changes on cash and cash equivalents		0
Change in Cash from discontinued operations		0
Net Decrease in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash	(293)	(67)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period	643	323
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	$ 350	$ 256