REGULATORY ASSETS AND LIABILITIES

The following regulatory assets were reflected on our balance sheets as of December 31:



(in millions)	2018		2017		See Note
Regulatory assets ^{(1) (2)}
Pension and OPEB costs ⁽³⁾	$	1,193.5	$	1,142.0	18
Plant retirements	832.3		15.1		6
Environmental remediation costs ⁽⁴⁾	687.1		676.6		22
Income tax related items ⁽⁵⁾	369.1		15.7		14
SSR	316.7		298.9		24
AROs	185.4		192.2		8
Electric transmission costs	58.1		221.0		24
We Power generation ⁽⁶⁾	43.0		71.3
Uncollectible expense ⁽⁷⁾	38.7		35.1		1(d)
Energy efficiency programs ⁽⁸⁾	14.0		24.6
Other, net	117.9		147.9
Total regulatory assets	$	3,855.8	$	2,840.4

Balance Sheet Presentation
Current assets	$	50.7	$	37.2
Regulatory assets	3,805.1		2,803.2
Total regulatory assets	$	3,855.8	$	2,840.4


⁽¹⁾	Based on prior and current rate treatment, we believe it is probable that our utilities will continue to recover from customers the regulatory assets in this table. In accordance with GAAP, our regulatory assets do not include the allowance for ROE that is capitalized for regulatory purposes. This allowance was $18.2 million and $17.7 million at December 31, 2018 and 2017, respectively.

⁽²⁾

As of December 31, 2018, we had $125.4 million of regulatory assets not earning a return, $104.1 million of regulatory assets earning a return based on short-term interest rates, and $316.7 million of regulatory assets earning a return based on long-term interest rates. The regulatory assets not earning a return primarily relate to certain environmental remediation costs, the recovery of which depends on the timing of the actual expenditures, as well as uncollectible expense, unamortized loss on reacquired debt, and our electric real-time market pricing program. The other regulatory assets in the table either earn a return or the cash has not yet been expended, in which case the regulatory assets are offset by liabilities.


⁽³⁾	Primarily represents the unrecognized future pension and OPEB costs related to our defined benefit pension and OPEB plans. We are authorized recovery of these regulatory assets over the average remaining service life of each plan.


⁽⁴⁾	As of December 31, 2018, we had made cash expenditures of $70.7 million related to these environmental remediation costs. The remaining $616.4 million represents our estimated future cash expenditures.


⁽⁵⁾	For information on the flow through of tax repairs and the regulatory treatment of the impacts of the Tax Legislation in our various jurisdictions, see Note 24, Regulatory Environment.


⁽⁶⁾	Represents amounts recoverable from customers related to WE's costs of the generating units leased from We Power, including subsequent capital additions.


⁽⁷⁾	Represents amounts recoverable from customers related to our uncollectible expense tracking mechanisms and riders. These mechanisms allow us to recover or refund the difference between actual uncollectible write-offs and the amounts recovered in rates.


⁽⁸⁾	Represents amounts recoverable from customers related to programs at the utilities designed to meet energy efficiency standards.

The following regulatory liabilities were reflected on our balance sheets as of December 31:



(in millions)	2018		2017		See Note
Regulatory liabilities
Income tax related items ⁽¹⁾	$	2,406.6	$	2,134.1	14
Removal costs ⁽²⁾	1,329.6		1,294.9
Pension and OPEB costs ⁽³⁾	238.3		114.2		18
Mines deferral ⁽⁴⁾	120.8		95.1
Energy costs refundable through rate adjustments ⁽⁵⁾	39.6		42.0
Energy efficiency programs ⁽⁶⁾	31.7		21.1
Uncollectible expense ⁽⁷⁾	30.5		24.7		1(d)
Decoupling	30.5		1.8		24
Earnings sharing mechanisms	30.0		2.5		24
Derivatives	16.4		11.0		1(o)
Other, net	14.4		19.0
Total regulatory liabilities	$	4,288.4	$	3,760.4

Balance Sheet Presentation
Current liabilities	$	36.8	$	41.8
Regulatory liabilities	4,251.6		3,718.6
Total regulatory liabilities	$	4,288.4	$	3,760.4


⁽¹⁾	For information on the regulatory treatment of the impacts of the Tax Legislation in our various jurisdictions, see Note 24, Regulatory Environment.


⁽²⁾	Represents amounts collected from customers to cover the future cost of property, plant, and equipment removals that are not legally required. Legal obligations related to the removal of property, plant, and equipment are recorded as AROs.


⁽³⁾	Primarily represents the unrecognized future pension and OPEB benefits related to our defined benefit pension and OPEB plans. We will amortize these regulatory liabilities into net periodic benefit cost over the average remaining service life of each plan.


⁽⁴⁾	Represents the deferral of revenues less the associated cost of sales related to Tilden, which were not included in the PSCW's 2015 rate order. We intend to request that this deferral be applied for the benefit of Wisconsin retail electric customers in a future rate proceeding.


⁽⁵⁾	Represents an over-collection of energy costs that will be refunded to customers in the future. When the rates we charge to customers include energy costs that are higher than our actual energy costs, any over-collection outside of the allowable energy cost price variance is refunded to customers.


⁽⁶⁾	Represents amounts refundable to customers related to programs at the utilities designed to meet energy efficiency standards.


⁽⁷⁾	Represents amounts refundable to customers related to our uncollectible expense tracking mechanisms and riders. These mechanisms allow us to recover or refund the difference between actual uncollectible write-offs and the amounts recovered in rates.