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 June 30, 2012		At September 30, 2011
Current regulatory assets
Unrealized losses on commodity derivatives	$	441	$	225
Deferred nuclear generating units	236		236
Environmental agreements	87		—
Environmental cleanup costs – Kingston ash spill	70		73
Fuel cost adjustment receivable	19		7
Deferred capital leases	1		2
Total current regulatory assets	854		543
Non-current regulatory assets
Deferred pension costs and other post-retirement benefits costs	5,537		5,807
Unrealized losses on swaps and swaption	1,350		1,164
Nuclear decommissioning costs	942		1,012
Environmental cleanup costs - Kingston ash spill	817		874
Construction costs	619		619
Non-nuclear decommissioning costs	548		519
Deferred nuclear generating units	532		709
Unrealized losses on commodity derivatives	446		221
Environmental agreements	251		346
Other non-current regulatory assets	361		234
Total non-current regulatory assets	11,403		11,505
Total regulatory assets	$	12,257	$	12,048

Current regulatory liabilities
Fuel cost adjustment tax equivalents	$	155	$	127
Unrealized gains on commodity derivatives	13		153
Total current regulatory liabilities	168		280
Non-current regulatory liabilities
Unrealized gains on commodity derivatives	113		285
Total non-current regulatory liabilities	113		285
Total regulatory liabilities	$	281	$	565