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, 2019		At September 30, 2018
Current regulatory assets
Gallatin coal combustion residual facilities⁽¹⁾	$	—	$	38
Unrealized losses on interest rate derivatives	85		73
Environmental agreements	—		3
Unrealized losses on commodity contracts	33		4
Environmental cleanup costs - Kingston ash spill	65		266
Fuel cost adjustment receivable	—		30
Total current regulatory assets	183		414

Non-current regulatory assets
Deferred pension costs and other post-retirement benefits costs	2,940		3,119
Non-nuclear decommissioning costs⁽¹⁾	1,761		1,019
Gallatin coal combustion residuals facilities⁽¹⁾	—		861
Nuclear decommissioning costs	847		784
Unrealized losses on interest rate derivatives	1,049		692
Environmental agreements	12		11
Unrealized losses on commodity contracts	9		8
Other non-current regulatory assets	137		118
Total non-current regulatory assets	6,755		6,612
Total regulatory assets	$	6,938	$	7,026

Current regulatory liabilities
Fuel cost adjustment tax equivalents	$	138	$	146
Fuel cost adjustment	10		—
Unrealized gains on commodity derivatives	13		41
Total current regulatory liabilities	161		187

Non-current regulatory liabilities
Deferred other post-retirement benefits cost	58		73
Unrealized gains on commodity derivatives	6		31
Total non-current regulatory liabilities	64		104
Total regulatory liabilities	$	225	$	291

Note

(1) See Note 9.