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, 2012		At September 30, 2012
Current regulatory assets
Unrealized losses on commodity derivatives	$	274	$	310
Deferred nuclear generating units	237		237
Environmental agreements	87		87
Environmental cleanup costs - Kingston ash spill	72		72
Fuel cost adjustment receivable	14		68
Total current regulatory assets	684		774

Non-current regulatory assets
Deferred pension costs and other post-retirement benefits costs	5,427		5,517
Unrealized losses on interest rate derivatives	1,218		1,332
Nuclear decommissioning costs	927		914
Environmental cleanup costs - Kingston ash spill	779		797
Construction costs	619		619
Non-nuclear decommissioning costs	563		550
Deferred nuclear generating units	414		473
Unrealized losses on commodity derivatives	317		335
Environmental agreements	237		237
Other non-current regulatory assets	349		353
Total non-current regulatory assets	10,850		11,127
Total regulatory assets	$	11,534	$	11,901

Current regulatory liabilities
Fuel cost adjustment tax equivalents	$	177	$	173
Unrealized gains on commodity derivatives	17		18
Total current regulatory liabilities	194		191

Non-current regulatory liabilities
Unrealized gains on commodity derivatives	99		109
Total non-current regulatory liabilities	99		109
Total regulatory liabilities	$	293	$	300