As of March 31, 2020, 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 2036 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 March 31, 2020, 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.

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, 2020 and December 31, 2019. 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 (In millions)
Category	Units	March 31, 2020	December 31, 2019
Emissions	Short Ton	1	3
Renewable Energy Certificates	Certificates	1	1
Coal	Short Ton	7	10
Natural Gas	MMBtu	(152)	(181)

Power	MWh	46	38
Capacity	MW/Day	(1)	(1)


	Fair Value
	Derivative Assets						Derivative Liabilities
(In millions)	March 31, 2020		December 31, 2019		March 31, 2020		December 31, 2019




Derivatives Not Designated as Cash Flow or Fair Value Hedges:


Commodity contracts current	$	884	$	860	$	832	$	781
Commodity contracts long-term	434		310		370		322
Total Derivatives Not Designated as Cash Flow or Fair Value Hedges	$	1,318	$	1,170	$	1,202	$	1,103

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
(In millions)	Gross Amounts of Recognized Assets / Liabilities		Derivative Instruments		Cash Collateral (Held) / Posted		Net Amount
As of March 31, 2020
Commodity contracts:
Derivative assets	$	1,318	$	(1,010)	$	(17)	$	291
Derivative liabilities	(1,202)		1,010		94		(98)
Total commodity contracts	$	116	$	—	$	77	$	193


	Gross Amounts Not Offset in the Statement of Financial Position
(In millions)	Gross Amounts of Recognized Assets / Liabilities		Derivative Instruments		Cash Collateral (Held) / Posted		Net Amount
As of December 31, 2019
Commodity contracts:
Derivative assets	$	1,170	$	(909)	$	(7)	$	254
Derivative liabilities	(1,103)		909		73		(121)
Total commodity contracts	$	67	$	—	$	66	$	133

Unrealized gains and losses associated with changes in the fair value of derivative instruments not accounted for as cash flow and fair value 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 or fair value 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.


(In millions)	Three months ended March 31,
Unrealized mark-to-market results	2020		2019
Reversal of previously recognized unrealized losses on settled positions related to economic hedges	$	9	$	19
Reversal of acquired loss/(gain) positions related to economic hedges	1		(2)
Net unrealized gains on open positions related to economic hedges	34		3
Total unrealized mark-to-market gains for economic hedging activities	44		20
Reversal of previously recognized unrealized (gains) on settled positions related to trading activity	(2)		(6)
Net unrealized gains on open positions related to trading activity	13		13
Total unrealized mark-to-market gains for trading activity	11		7
Total unrealized gains	$	55	$	27


	Three months ended March 31,
(In millions)	2020		2019
Unrealized gains included in operating revenues	$	7	$	27
Unrealized gains included in cost of operations	48		—
Total impact to statement of operations — energy commodities	$	55	$	27
Total impact to statement of operations — interest rate contracts	$	—	$	(9)

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, 2020, the $34 million unrealized gain from open economic hedge positions was primarily the result of an increase in value of forward power positions due to a decrease in West/Other power prices, as well as an increase in value of ERCOT heat rate positions due to ERCOT heat rate expansion.

For the three months ended March 31, 2019, the $3 million unrealized gain from open economic hedge positions was primarily the result of an increase in value of forward power positions due to a decrease in 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 March 31, 2020 was $12 million. The collateral required for contracts with credit rating contingent features that are in a net liability position as of March 31, 2020 was $25 million. The Company is also a party to certain marginable agreements under which it