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ASSET RETIREMENT OBLIGATIONS (Tables)

12 Months Ended

Dec. 31, 2023

Asset Retirement Obligation Disclosure [Abstract]

Details of AROs included in the balance sheets

Details of the AROs included in the balance sheets are as follows:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power(*)
	(in millions)
Balance at December 31, 2021	$	11,687	$	4,334	$	6,824	$	190	$	131
Liabilities incurred	36		—		35		—		—
Liabilities settled	(455)		(205)		(212)		(20)		—
Accretion expense	406		158		231		6		6
Cash flow revisions	(834)		—		(844)		3		7
Balance at December 31, 2022	$	10,840	$	4,287	$	6,034	$	179	$	144
Liabilities incurred	90		—		90		—		—
Liabilities settled	(617)		(270)		(304)		(18)		—
Accretion expense	403		156		230		5		6
Cash flow revisions	(399)		(15)		(385)		2		—
Balance at December 31, 2023	$	10,317	$	4,158	$	5,665	$	168	$	150

(*)Included in other deferred credits and liabilities on Southern Power's consolidated balance sheets.

Investment securities in the Funds

Investment securities in the Funds for December 31, 2023 and 2022 were as follows:


	Southern Company		Alabama Power		Georgia Power
	(in millions)
At December 31, 2023:
Equity securities	$	1,288	$	796	$	492
Debt securities	895		277		618
Other securities	239		186		53
Total investment securities in the Funds	$	2,422	$	1,259	$	1,163

At December 31, 2022:
Equity securities	$	1,095	$	690	$	405
Debt securities	838		267		571
Other securities	210		168		42
Total investment securities in the Funds(*)	$	2,143	$	1,125	$	1,018

(*)For Southern Company and Georgia Power, these amounts include investment securities pledged to creditors and collateral received and excludes payables related to a securities lending program Georgia Power's Funds previously participated in through the managers of the Funds. Under this program, Georgia Power's Funds' investment securities were loaned to institutional investors for a fee. Securities loaned were fully collateralized by cash, letters of credit, and/or securities issued or guaranteed by the U.S. government or its agencies or instrumentalities. At December 31, 2022, approximately $35 million of the fair market value of Georgia Power's Funds' securities were on loan and pledged to creditors under the Funds' managers' securities lending program. At December 31, 2022, the fair value of the collateral received was approximately $36 million and could only be sold by the borrower upon the return of the loaned securities. The collateral received was treated as a non-cash item in the statements of cash flows.

Fair value increases (decreases) of the Funds

The fair value increases (decreases) of the Funds, including unrealized gains (losses) and reinvested interest and dividends and excluding the Funds' expenses, for 2023, 2022, and 2021 are shown in the table below.


	Southern Company		Alabama Power		Georgia Power
	(in millions)
Fair value increases (decreases)
2023	$	281	$	157	$	124
2022	(360)		(171)		(189)
2021	274		200		74

Unrealized gains (losses)
At December 31, 2023	$	241	$	119	$	122
At December 31, 2022	(391)		(204)		(187)
At December 31, 2021	(27)		(30)		3

At December 31, 2023, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2023:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Company
Assets:
Energy-related derivatives(a)	$	6	$	49	$	—	$	—	$	55


Investments in trusts:(b)
Domestic equity	764		216		—		—		980
Foreign equity	145		171		—		—		316
U.S. Treasury and government agency securities	—		369		—		—		369
Municipal bonds	—		48		—		—		48
Pooled funds – fixed income	—		6		—		—		6
Corporate bonds	—		389		—		—		389
Mortgage and asset backed securities	—		89		—		—		89
Private equity	—		—		—		169		169
Cash and cash equivalents	3		—		—		—		3
Other	58		3		—		9		70
Cash equivalents and restricted cash	253		15		—		—		268
Other investments	9		27		8		—		44
Total	$	1,238	$	1,382	$	8	$	178	$	2,806
Liabilities:
Energy-related derivatives(a)	$	46	$	312	$	—	$	—	$	358
Interest rate derivatives	—		264		—		—		264
Foreign currency derivatives	—		122		—		—		122
Contingent consideration	3		—		16		—		19
Other	—		13		—		—		13
Total	$	49	$	711	$	16	$	—	$	776


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2023:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Alabama Power
Assets:
Energy-related derivatives	$	—	$	15	$	—	$	—	$	15
Nuclear decommissioning trusts:(b)
Domestic equity	443		208		—		—		651
Foreign equity	145		—		—		—		145
U.S. Treasury and government agency securities	—		20		—		—		20
Municipal bonds	—		1		—		—		1
Corporate bonds	—		231		—		—		231
Mortgage and asset backed securities	—		25		—		—		25
Private equity	—		—		—		169		169
Other	8		—		—		9		17
Cash equivalents and restricted cash	119		15		—		—		134
Other investments	—		27		—		—		27
Total	$	715	$	542	$	—	$	178	$	1,435
Liabilities:
Energy-related derivatives	$	—	$	110	$	—	$	—	$	110

Georgia Power
Assets:
Energy-related derivatives	$	—	$	13	$	—	$	—	$	13

Nuclear decommissioning trusts:(b)
Domestic equity	321		1		—		—		322
Foreign equity	—		170		—		—		170
U.S. Treasury and government agency securities	—		349		—		—		349
Municipal bonds	—		47		—		—		47
Corporate bonds	—		158		—		—		158
Mortgage and asset backed securities	—		64		—		—		64
Other	50		3		—		—		53

Total	$	371	$	805	$	—	$	—	$	1,176
Liabilities:
Energy-related derivatives	$	—	$	124	$	—	$	—	$	124


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2023:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Mississippi Power
Assets:
Energy-related derivatives	$	—	$	15	$	—	$	—	$	15

Cash equivalents	17		—		—		—		17
Total	$	17	$	15	$	—	$	—	$	32
Liabilities:
Energy-related derivatives	$	—	$	61	$	—	$	—	$	61

Southern Power
Assets:
Energy-related derivatives	$	—	$	3	$	—	$	—	$	3




Liabilities:
Energy-related derivatives	$	—	$	5	$	—	$	—	$	5
Foreign currency derivatives	—		22		—		—		22
Contingent consideration	3		—		16		—		19
Other	—		13		—		—		13
Total	$	3	$	40	$	16	$	—	$	59

Southern Company Gas
Assets:
Energy-related derivatives(a)	$	6	$	3	$	—	$	—	$	9

Non-qualified deferred compensation trusts:
Domestic equity	—		7		—		—		7
Foreign equity	—		1		—		—		1
Pooled funds - fixed income	—		6		—		—		6
Cash and cash equivalents	3		—		—		—		3

Total	$	9	$	17	$	—	$	—	$	26
Liabilities:
Energy-related derivatives(a)(b)	$	46	$	12	$	—	$	—	$	58
Interest rate derivatives	—		79		—		—		79
Total	$	46	$	91	$	—	$	—	$	137

(a)Excludes cash collateral of $62 million.

(b)Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 under "Nuclear Decommissioning" for additional information.

At December 31, 2022, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Company
Assets:
Energy-related derivatives(a)	$	18	$	181	$	—	$	—	$	199
Interest rate derivatives	—		12		—		—		12

Investments in trusts:(b)(c)
Domestic equity	651		178		—		—		829
Foreign equity	125		150		—		—		275
U.S. Treasury and government agency securities	—		285		—		—		285
Municipal bonds	—		51		—		—		51
Pooled funds – fixed income	—		7		—		—		7
Corporate bonds	—		412		—		—		412
Mortgage and asset backed securities	—		90		—		—		90
Private equity	—		—		—		161		161
Cash and cash equivalents	4		—		—		—		4
Other	37		12		—		—		49
Cash equivalents	1,427		20		—		—		1,447
Other investments	9		26		—		—		35
Total	$	2,271	$	1,424	$	—	$	161	$	3,856
Liabilities:
Energy-related derivatives(a)	$	32	$	178	$	—	$	—	$	210
Interest rate derivatives	—		302		—		—		302
Foreign currency derivatives	—		216		—		—		216
Contingent consideration	—		—		12		—		12
Other	—		13		—		—		13
Total	$	32	$	709	$	12	$	—	$	753


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Alabama Power
Assets:
Energy-related derivatives	$	—	$	62	$	—	$	—	$	62
Nuclear decommissioning trusts:(b)
Domestic equity	396		169		—		—		565
Foreign equity	125		—		—		—		125
U.S. Treasury and government agency securities	—		19		—		—		19
Municipal bonds	—		1		—		—		1
Corporate bonds	—		225		—		—		225
Mortgage and asset backed securities	—		22		—		—		22
Private equity	—		—		—		161		161
Other	7		—		—		—		7
Cash equivalents	438		20		—		—		458
Other investments	—		26		—		—		26
Total	$	966	$	544	$	—	$	161	$	1,671
Liabilities:

Energy-related derivatives	$	—	$	39	$	—	$	—	$	39

Georgia Power
Assets:
Energy-related derivatives	$	—	$	42	$	—	$	—	$	42

Nuclear decommissioning trusts:(b)(c)
Domestic equity	255		1		—		—		256
Foreign equity	—		149		—		—		149
U.S. Treasury and government agency securities	—		266		—		—		266
Municipal bonds	—		50		—		—		50
Corporate bonds	—		187		—		—		187
Mortgage and asset backed securities	—		68		—		—		68
Other	30		12		—		—		42
Cash equivalents	355		—		—		—		355
Total	$	640	$	775	$	—	$	—	$	1,415
Liabilities:
Energy-related derivatives	$	—	$	62	$	—	$	—	$	62


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs		Net Asset Value as a Practical Expedient
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Mississippi Power
Assets:
Energy-related derivatives	$	—	$	59	$	—	$	—	$	59

Cash equivalents	47		—		—		—		47
Total	$	47	$	59	$	—	$	—	$	106
Liabilities:
Energy-related derivatives	$	—	$	32	$	—	$	—	$	32



Southern Power
Assets:
Energy-related derivatives	$	—	$	8	$	—	$	—	$	8



Liabilities:
Energy-related derivatives	$	—	$	12	$	—	$	—	$	12
Foreign currency derivatives	—		47		—		—		47
Contingent consideration	—		—		12		—		12
Other	—		13		—		—		13
Total	$	—	$	72	$	12	$	—	$	84

Southern Company Gas
Assets:
Energy-related derivatives(a)	$	18	$	10	$	—	$	—	$	28

Non-qualified deferred compensation trusts:
Domestic equity	—		8		—		—		8
Foreign equity	—		1		—		—		1
Pooled funds - fixed income	—		7		—		—		7
Cash equivalents	4		—		—		—		4
Cash equivalents	50		—		—		—		50
Total	$	72	$	26	$	—	$	—	$	98
Liabilities:
Energy-related derivatives(a)(b)	$	32	$	33	$	—	$	—	$	65
Interest rate derivatives	—		86		—		—		86
Total	$	32	$	119	$	—	$	—	$	151

(a)Excludes cash collateral of $41 million.

(c)Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. See Note 6 under "Nuclear Decommissioning" for additional information.

Accumulated provisions for the external decommissioning trust funds

At December 31, 2023 and 2022, the accumulated provisions for the external decommissioning trust funds were as follows:


	2023		2022
	(in millions)
Alabama Power
Plant Farley	$	1,259	$	1,125

Georgia Power
Plant Hatch	$	705	$	628
Plant Vogtle Units 1 and 2	434		382
Plant Vogtle Units 3 and 4	24		8
Total	$	1,163	$	1,018

Estimated costs of decommissioning

The estimated costs of decommissioning at December 31, 2023 based on the most current studies were as follows:


	Alabama Power		Georgia Power
	Plant Farley		Plant Hatch(*)		Plant Vogtle Units 1 and 2(*)		Plant Vogtle Unit 3(*)
Most current study year	2023		2021		2021		2020
Decommissioning periods:
Beginning year	2037		2034		2047		2063
Completion year	2087		2075		2079		2074
	(in millions)
Site study costs:
Radiated structures	$	1,402	$	771	$	628	$	284
Spent fuel management	513		186		170		30
Non-radiated structures	133		61		85		33
Total site study costs	$	2,048	$	1,018	$	883	$	347

(*)Based on Georgia Power's ownership interests.