Details of the regulatory assets and liabilities are presented in the following table:

Regulatory Assets and Liabilities
(millions)	September 30, 2017		December 31, 2016
Regulatory assets:
Regulatory tax asset ⁽¹⁾	$	83	$	86
Cost-recovery clauses - deferred balances ⁽²⁾		7		8
Environmental remediation⁽³⁾		33		37
Postretirement benefits ⁽⁴⁾		276		272
Storm reserve ⁽⁵⁾		14		0
Other		22		18
Total regulatory assets		435		421
Less: Current portion		38		28
Long-term regulatory assets	$	397	$	393
Regulatory liabilities:
Regulatory tax liability	$	12	$	6
Cost-recovery clauses - deferred balances ⁽²⁾		38		112
Cost-recovery clauses - offsets to derivative assets⁽²⁾		0		17
Storm reserve ⁽⁵⁾		0		56
Accumulated reserve - cost of removal⁽⁶⁾		524		547
Other		7		7
Total regulatory liabilities		581		745
Less: Current portion		65		154
Long-term regulatory liabilities	$	516	$	591

(1)

The regulatory tax asset is primarily associated with the depreciation and recovery of AFUDC-equity. This asset does not earn a return but rather is included in the capital structure, which is used in the calculation of the weighted cost of capital used to determine revenue requirements. It will be recovered over the expected life of the related assets.

(2)

These assets and liabilities are related to FPSC clauses and riders. They are recovered or refunded through cost-recovery mechanisms approved by the FPSC on a dollar-for-dollar basis in the next year. In the case of the regulatory liability related to derivative assets, refund occurs in the year following the settlement of the derivative position.

(3)

This asset is related to costs associated with environmental remediation primarily at MGP sites. The balance is included in rate base, partially offsetting the related liability, and earns a rate of return as permitted by the FPSC. The timing of recovery is based on a settlement agreement approved by the FPSC.

(4)

This asset is related to the deferred costs of postretirement benefits and it is amortized over the remaining service life of plan participants. Deferred costs of postretirement benefits that are included in expense are recognized as cost of service for rate-making purposes as permitted by the FPSC.

(5)	See Tampa Electric Storm Restoration Cost Recovery above for information regarding this reserve. The regulatory asset is included in rate base and earns a rate of return as permitted by the FPSC. The asset will be recovered over a 12-month period.

(6)

This item represents the non-ARO cost of removal in the accumulated reserve for depreciation. AROs are costs for legally required removal of property, plant and equipment. Non-ARO cost of removal represents estimated funds received from customers through depreciation rates to cover future non-legally required cost of removal of property, plant and equipment, net of salvage value upon retirement, which reduces rate base for ratemaking purposes. This liability is reduced as costs of removal are incurred.