As of September 30, 2019, NRG had energy-related derivative instruments extending through 2034. The Company marks these derivatives to market through the statement of operations. NRG has executed power purchase agreements extending through 2033 that qualified for the NPNS exception and were therefore exempt from fair value accounting treatment.

NRG was 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 entered into interest rate swap agreements. As of September 30, 2019, NRG had no interest rate derivative instruments as a result of the early termination of such contracts in connection with the repayment of the 2023 Term Loan Facility during the second quarter of 2019. See Note 10, Debt and Finance Leases, for further discussion.

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 September 30, 2019 and December 31, 2018. 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
		September 30, 2019		December 31, 2018
Category	Units	(In millions)
Emissions	Short Ton	2		(2)
Renewable Energy Certificates	Certificates	1		1
Coal	Short Ton	4		13
Natural Gas	MMBtu	(273)		(330)
Oil	Barrels	—		1
Power	MWh	37		1
Capacity	MW/Day	(1)		(1)
Interest	Dollars	$	—	$	1,000

The decrease in the natural gas position was primarily the result of additional retail hedge positions and settlement of generation hedges. The increase in the power position was primarily the result of additional retail hedge positions and the settlement of generation hedges. The decrease in the interest position was the result of the early settlement of the interest rate swaps.


	Fair Value
	Derivative Assets						Derivative Liabilities
	September 30, 2019		December 31, 2018		September 30, 2019		December 31, 2018
	(In millions)




Derivatives Not Designated as Cash Flow or Fair Value Hedges:
Interest rate contracts current	$	—	$	17	$	—	$	—
Interest rate contracts long-term	—		22		—		—
Commodity contracts current	735		747		668		673
Commodity contracts long-term	358		295		364		304
Total Derivatives Not Designated as Cash Flow or Fair Value Hedges	$	1,093	$	1,081	$	1,032	$	977

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 September 30, 2019 Balance Sheet
	Gross Amounts of Recognized Assets / Liabilities		Derivative Instruments		Cash Collateral (Held) / Posted		Net Amount
	(In millions)
Commodity contracts:
Derivative assets	$	1,093	$	(869)	$	(5)	$	219
Derivative liabilities	(1,032)		869		70		(93)
Total commodity contracts	$	61	$	—	$	65	$	126


	Gross Amounts Not Offset in the December 31, 2018 Balance Sheet
	Gross Amounts of Recognized Assets / Liabilities		Derivative Instruments		Cash Collateral (Held) / Posted		Net Amount
	(In millions)
Commodity contracts:
Derivative assets	$	1,042	$	(778)	$	(31)	$	233
Derivative liabilities	(977)		778		114		(85)
Total commodity contracts	65		—		83		148
Interest rate contracts:
Derivative assets	39		—		—		39

Total interest rate contracts	39		—		—		39


Total derivative instruments	$	104	$	—	$	83	$	187


	Interest Rate Contracts
	Three months ended		Nine months ended
	September 30, 2018		September 30, 2018

	(In millions)
Accumulated OCL beginning balance	$	(23)	$	(54)
Reclassified from accumulated OCL to income:
Due to realization of previously deferred amounts	1		8
Mark-to-market of cash flow hedge accounting contracts	(3)		21
Sale of NRG Yield and Renewables Platform	25		25
Accumulated OCL ending balance, net of $0 tax	$	—	$	—

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 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 commodity hedges is included within operating revenues and cost of operations and the effect of interest rate hedges is included in interest expense.


	Three months ended September 30,						Nine months ended September 30,
	2019		2018		2019		2018
Unrealized mark-to-market results	(In millions)
Reversal of previously recognized unrealized (gains) on settled positions related to economic hedges	$	(118)	$	(84)	$	(88)	$	(85)
Reversal of acquired (gain) positions related to economic hedges	(3)		(10)		(4)		(11)
Net unrealized gains on open positions related to economic hedges	57		26		69		158
Total unrealized mark-to-market (losses)/gains for economic hedging activities	(64)		(68)		(23)		62
Reversal of previously recognized unrealized (gains) on settled positions related to trading activity	(1)		(4)		(8)		(10)
Net unrealized (losses)/gains on open positions related to trading activity	(3)		8		23		27
Total unrealized mark-to-market (losses)/gains for trading activity	(4)		4		15		17
Total unrealized (losses)/gains	$	(68)	$	(64)	$	(8)	$	79


	Three months ended September 30,						Nine months ended September 30,
	2019		2018		2019		2018
	(In millions)
Unrealized (losses)/ gains included in operating revenues	$	(214)	$	59	$	66	$	(14)
Unrealized gains/(losses) included in cost of operations	146		(123)		(74)		93
Total impact to statement of operations — energy commodities	$	(68)	$	(64)	$	(8)	$	79
Total impact to statement of operations — interest rate contracts	$	—	$	2	$	(38)	$	17

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 nine months ended September 30, 2019, the $69 million unrealized gain from open economic hedge positions was primarily the result of an increase in value of forward purchases of ERCOT heat rate due to ERCOT heat rate expansion.

For the nine months ended September 30, 2018, the $158 million unrealized gain from open economic hedge positions was primarily the result of an increase in value of forward purchases of ERCOT heat rate and ERCOT electricity contracts due to ERCOT heat rate expansion and increases in ERCOT power prices.

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 September 30, 2019 was $39 million. The collateral required for contracts with credit rating contingent features that are in a net liability position as of September 30, 2019 was $18 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 $2 million as of September 30, 2019.