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 deferral 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 March 31, 2012		At September 30, 2011
Current regulatory assets
Unrealized losses on commodity derivatives	$	535	$	225
Deferred nuclear generating units	236		236
Environmental agreements	87		—
Environmental cleanup costs – Kingston ash spill	71		73
Deferred capital leases	1		2
Fuel cost adjustment receivable	—		7
Total current regulatory assets	930		543
Non-current regulatory assets
Deferred pension costs and other post-retirement benefits costs	5,627		5,807
Unrealized losses on swaps and swaptions	1,025		1,164
Nuclear decommissioning costs	894		1,012
Environmental cleanup costs - Kingston ash spill	835		874
Construction costs	619		619
Deferred nuclear generating units	591		709
Non-nuclear decommissioning costs	527		519
Unrealized losses on commodity derivatives	470		221
Environmental agreements	253		346
Other non-current regulatory assets	299		234
Total non-current regulatory assets	11,140		11,505
Total regulatory assets	$	12,070	$	12,048

Current regulatory liabilities
Fuel cost adjustment tax equivalents	$	143	$	127
Fuel cost adjustment liability	48		—
Unrealized gains on commodity derivatives	28		153
Total current regulatory liabilities	219		280
Non-current regulatory liabilities
Unrealized gains on commodity derivatives	127		285
Total regulatory liabilities	$	346	$	565