Regulatory Assets and Liabilities

Regulatory assets generally represent incurred costs that have been deferred because such costs are probable of future recovery in customer rates. Regulatory liabilities generally represent obligations to make refunds to customers for previous collections for costs that are not likely to be incurred or deferrals of gains that will be credited to customers in future periods. Components of regulatory assets and regulatory liabilities are summarized in the table below:



Regulatory Assets and Liabilities
	At December 31, 2014		At September 30, 2014
Current regulatory assets
Deferred nuclear generating units	$	237	$	237
Unrealized losses on commodity derivatives	205		134
Environmental agreements	62		54
Environmental cleanup costs - Kingston ash spill	45		47
Fuel cost adjustment receivable	15		9
Total current regulatory assets	564		481

Non-current regulatory assets
Deferred pension costs and other post-retirement benefits costs	4,235		4,297
Deferred pension costs due to actions of regulator	51		—
Unrealized losses on interest rate derivatives	1,141		957
Nuclear decommissioning costs	908		931
Environmental cleanup costs - Kingston ash spill	360		421
Non-nuclear decommissioning costs	651		645
Deferred nuclear generating units	1,209		1,255
Environmental agreements	91		108
Unrealized losses on commodity derivatives	97		72
Other non-current regulatory assets	300		308
Total non-current regulatory assets	9,043		8,994
Total regulatory assets	$	9,607	$	9,475

Current regulatory liabilities
Fuel cost adjustment tax equivalents	$	174	$	182
Unrealized gains on commodity derivatives	—		2
Total current regulatory liabilities	174		184
Total regulatory liabilities	$	174	$	184

Deferred Pension Costs Due to Actions of Regulator. In 2015, TVA began including its cash contributions to the pension plan in the rate-making formula; accordingly, on October 1, 2014, TVA began recognizing pension costs as regulatory assets to the extent that the amount calculated under GAAP as pension expense differs from the amount TVA contributes to the pension plan.