Regulatory Assets and Liabilities (Tables)

3 Months Ended

Mar. 31, 2024

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of regulatory assets and liabilities

The following regulatory assets and liabilities are reflected on the consolidated balance sheets as of March 31, 2024 and December 31, 2023.

	2024		2023
	(dollars in thousands)
Regulatory Assets:
Premium and loss on reacquired debt(a)	$	24,504	$	25,476
Amortization of financing leases(b)	27,760		28,780
Outage costs(c)	34,627		30,040
Asset retirement obligations—Ashpond and other(l)	338,752		343,523
Depreciation expense - Plant Vogtle(d)	33,770		34,125
Depreciation expense - Plant Wansley(e)	330,945		335,884
Deferred charges related to Vogtle Units No. 3 and No. 4 training costs(f)	55,528		55,159
Interest rate options cost(g)	135,561		137,463
Deferral of effects on net margin—TA Smith Energy Facility(h)	129,299		130,786
Deferral of effects on net margin—BC Smith Energy Facility(p)	9,379		1,817
Other regulatory assets(o)	16,123		8,436
Total Regulatory Assets	$	1,136,248	$	1,131,489
Regulatory Liabilities:
Accumulated retirement costs for other obligations(i)	$	23,455	$	25,992
Deferral of effects on net margin—Hawk Road Energy Facility(h)	15,866		16,020
Major maintenance reserve(j)	114,484		120,547
Deferred debt service adder(k)	174,507		170,466
Asset retirement obligations—Nuclear(l)	82,606		47,217
Revenue deferral plan(m)	279,467		308,507
Natural gas hedges(n)	10,381		13,445
Other regulatory liabilities(o)	3,318		4,126
Total Regulatory Liabilities	$	704,084	$	706,320
Net Regulatory Assets	$	432,164	$	425,169

(a)Represents premiums paid, together with unamortized transaction costs related to reacquired debt that are being amortized over the lives of the refunding debt, which range up to 20 years.

(b)Represents the difference between expense recognized for rate-making purposes versus financial statement purposes related to finance lease payments and the aggregate of the amortization of the asset and interest on the obligation.

(c)Consists of both coal-fired maintenance and nuclear refueling outage costs. Coal-fired outage costs are amortized on a straight-line basis to expense over periods up to 60 months, depending on the operating cycle of each unit. Nuclear refueling outage costs are amortized on a straight-line basis to expense over the 18 or 24-month operating cycles of each unit.

(d)Prior to Nuclear Regulatory Commission (NRC) approval of a 20-year license extension for Plant Vogtle, we deferred the difference between Plant Vogtle depreciation expense based on the then 40-year operating license and depreciation expense assuming an expected 20-year license extension. Amortization commenced upon NRC approval of the license extension in 2009 and is being amortized over the remaining life of the plant.

(e)Represents the deferral of accelerated depreciation associated with the early retirement of Plant Wansley, which occurred on August 31, 2022. Amortization commenced upon the retirement of Plant Wansley and will end no later than December 31, 2040.

(f)Deferred charges consist of training related costs, including interest and carrying costs of such training. Amortization commences effective with the commercial operation date of each unit and is amortized to expense over the life of the units.

(g)Deferral of premiums paid to purchase interest rate options used to hedge interest rates on certain borrowings, related carrying costs and other incidentals associated with construction of Vogtle Units No. 3 and No. 4. Amortization commenced in August 2023 after Vogtle Unit No. 3 was placed in service.

(h)Effects on net margin for TA Smith and Hawk Road Energy Facilities were deferred through the end of 2015 and are being amortized over the remaining life of each respective plant.

(i)Represents the accrual of retirement costs associated with long-lived assets for which there are no legal obligations to retire the assets.

(j)Represents collections for future major maintenance costs; revenues are recognized as major maintenance costs are incurred.

(k)Represents collections to fund certain debt payments to be made through the end of 2025 which will be in excess of amounts collected through depreciation expense; the deferred credits will be amortized over the remaining useful life of the plants.

(l)Represents the difference in the timing of recognition of decommissioning costs for financial statement purposes versus ratemaking purposes, as well as the deferral of unrealized gains and losses of funds set aside for decommissioning.

(m)Deferred revenues under a rate management program that allowed for additional collections over a five-year period which began in 2018. These amounts are being amortized to income and applied to member billings, per each members' election, over the subsequent five-year period.

(n)Represents the deferral of unrealized gains on natural gas contracts.

(o)The amortization periods for other regulatory assets range up to 30 years and the amortization periods of other regulatory liabilities range up to 24 years.

(p)Effects on net margin for the BC Smith Energy Facility that are being deferred until on or before January 2026 and will be amortized over the remaining life of the plant.