REGULATORY ASSETS AND LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2023

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of regulatory assets

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

(in millions)	2023		2022		See Note
Regulatory assets (1) (2)
Environmental remediation costs (3)	$	121.5	$	118.5	21
Pension and OPEB costs (4)	62.0		48.6		19, 23
Income tax related items	57.2		61.5		16
Plant retirement related items	38.4		43.1
AROs	18.8		15.6		1(k), 9
Derivatives	12.5		22.5		1(p)
Bluewater (5)	11.9		6.8
ReACT™	10.4		13.0		23
Uncollectible expense	8.9		5.6		5
Energy efficiency programs (6)	5.5		13.4
Other, net	13.5		16.9
Total regulatory assets	$	360.6	$	365.5

(1)    Based on prior and current rate treatment, we believe it is probable that we 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 $7.7 million and $9.6 million at December 31, 2023 and 2022, respectively.

(2)    As of December 31, 2023, we had $36.2 million of regulatory assets not earning a return. The regulatory assets not earning a return relate to certain environmental remediation costs. The other regulatory assets in the table either earn a return at our weighted average cost of capital or the cash has not yet been expended, in which case the regulatory assets are offset by liabilities.

(3)    As of December 31, 2023, we had made cash expenditures of $36.2 million related to these environmental remediation costs. The remaining $85.3 million represents our estimated future cash expenditures.

(4)    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.

(5)    Primarily relates to costs associated with our long-term service agreement with Bluewater for natural gas storage services. The PSCW has approved escrow accounting for these costs. As a result, we defer as a regulatory asset or liability the difference between actual storage costs and those included in rates until recovery or refund is authorized in a future rate proceeding.

(6)    Represents amounts recoverable from customers related to programs designed to meet energy efficiency standards.

Schedule of regulatory liabilities

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

(in millions)	2023		2022		See Note
Regulatory liabilities
Income tax related items	$	331.4	$	343.7	16
Removal costs (1)	191.2		186.5
Pension and OPEB benefits (2)	85.3		90.1		19, 23
Energy costs refundable through rate adjustments	36.3		9.9		1(d)
Derivatives	4.1		7.9		1(p)
Other, net	32.2		22.1
Total regulatory liabilities	$	680.5	$	660.2
Balance sheet presentation
Other current liabilities	$	8.5	$	9.9
Regulatory liabilities	672.0		650.3
Total regulatory liabilities	$	680.5	$	660.2

(1)    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. See Note 9, Asset Retirement Obligations, for more information on our legal obligations.

(2)     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.