Regulatory Assets and Liabilities

6 Months Ended

Mar. 31, 2019

Regulatory Assets and Liabilities Disclosure [Abstract]

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, 2019		At September 30, 2018
Current regulatory assets
Gallatin coal combustion residual facilities	$	26	$	38
Unrealized losses on interest rate derivatives	78		73
Environmental agreements	—		3
Unrealized losses on commodity contracts	7		4
Environmental cleanup costs – Kingston ash spill	130		266
Fuel cost adjustment receivable	—		30
Total current regulatory assets	241		414

Non-current regulatory assets
Deferred pension costs and other post-retirement benefits costs	3,000		3,119
Non-nuclear decommissioning costs	1,054		1,019
Nuclear decommissioning costs	856		784
Gallatin coal combustion residual facilities	864		861
Unrealized losses on interest rate derivatives	897		692
Environmental agreements	12		11
Unrealized losses on commodity contracts	7		8
Other non-current regulatory assets	132		118
Total non-current regulatory assets	6,822		6,612
Total regulatory assets	$	7,063	$	7,026

Current regulatory liabilities
Fuel cost adjustment tax equivalents	$	144	$	146
Fuel cost adjustment	19		—
Unrealized gains on commodity derivatives	32		41
Total current regulatory liabilities	195		187

Non-current regulatory liabilities
Deferred other post-retirement benefits cost	63		73
Unrealized gains on commodity derivatives	10		31
Total non-current regulatory liabilities	73		104
Total regulatory liabilities	$	268	$	291