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RETIREMENT BENEFITS (Tables)

12 Months Ended

Dec. 31, 2023

The weighted average rates assumed in the actuarial calculations used to determine both the net periodic costs for the pension and other postretirement benefit plans for the following year and the benefit obligations as of the measurement date are presented below.


	2023
Assumptions used to determine net periodic costs:	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
Pension plans
Discount rate – benefit obligations	5.25	%	5.26	%	5.25	%	5.25	%	5.31	%	5.24	%
Discount rate – interest costs	5.13		5.14		5.12		5.12		5.19		5.12
Discount rate – service costs	5.36		5.38		5.38		5.37		5.37		5.31
Expected long-term return on plan assets	8.40		8.40		8.40		8.40		8.40		8.40
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80
Other postretirement benefit plans
Discount rate – benefit obligations	5.18	%	5.20	%	5.17	%	5.17	%	5.24	%	5.16	%
Discount rate – interest costs	5.08		5.09		5.07		5.08		5.12		5.07
Discount rate – service costs	5.34		5.35		5.34		5.33		5.33		5.33
Expected long-term return on plan assets	7.67		7.95		7.49		7.43		—		6.59
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80


	2022
Assumptions used to determine net periodic costs:	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
Pension plans
Discount rate – benefit obligations	3.09	%	3.12	%	3.07	%	3.07	%	3.21	%	3.04	%
Discount rate – interest costs	2.55		2.58		2.51		2.54		2.79		2.53
Discount rate – service costs	3.34		3.36		3.37		3.35		3.36		3.21
Expected long-term return on plan assets	8.25		8.25		8.25		8.25		8.25		8.25
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80
Other postretirement benefit plans
Discount rate – benefit obligations	2.90	%	2.95	%	2.87	%	2.88	%	3.07	%	2.82	%
Discount rate – interest costs	2.32		2.38		2.30		2.27		2.55		2.17
Discount rate – service costs	3.26		3.30		3.27		3.26		3.25		3.22
Expected long-term return on plan assets	7.21		7.54		6.88		7.22		—		6.08
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80


	2021
Assumptions used to determine net periodic costs:	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
Pension plans
Discount rate – benefit obligations	2.81	%	2.85	%	2.79	%	2.80	%	2.99	%	2.75	%
Discount rate – interest costs	2.13		2.17		2.09		2.12		2.46		2.10
Discount rate – service costs	3.18		3.23		3.21		3.20		3.22		2.97
Expected long-term return on plan assets	8.25		8.25		8.25		8.25		8.25		8.25
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80
Other postretirement benefit plans
Discount rate – benefit obligations	2.56	%	2.63	%	2.52	%	2.53	%	2.78	%	2.46	%
Discount rate – interest costs	1.84		1.91		1.82		1.78		2.12		1.64
Discount rate – service costs	3.07		3.13		3.08		3.06		3.05		3.01
Expected long-term return on plan assets	7.09		7.18		6.84		6.98		—		6.54
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80


	2023
Assumptions used to determine benefit obligations:	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
Pension plans
Discount rate	5.07	%	5.08	%	5.06	%	5.06	%	5.14	%	5.05	%
Annual salary increase	4.60		4.60		4.60		4.60		4.60		4.60
Other postretirement benefit plans
Discount rate	4.99	%	5.01	%	4.98	%	4.98	%	5.06	%	4.98	%
Annual salary increase	4.60		4.60		4.60		4.60		4.60		4.60


	2022
Assumptions used to determine benefit obligations:	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
Pension plans
Discount rate	5.25	%	5.26	%	5.25	%	5.25	%	5.31	%	5.24	%
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80
Other postretirement benefit plans
Discount rate	5.18	%	5.20	%	5.17	%	5.17	%	5.24	%	5.16	%
Annual salary increase	4.80		4.80		4.80		4.80		4.80		4.80

Schedule of health care cost trend rates

The weighted average medical care cost trend rates used in measuring the APBO for the Registrants at December 31, 2023 were as follows:


	Initial Cost Trend Rate		Ultimate Cost Trend Rate		Year That Ultimate Rate is Reached
Pre-65	7.00	%	4.50	%	2032
Post-65 medical	5.50		4.50		2032
Post-65 prescription	8.50		4.50		2032

Schedule of accumulated and projected benefit obligations

The total accumulated benefit obligation for the pension plans at December 31, 2023 and 2022 was as follows:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
December 31, 2023	$	11,991	$	2,746	$	3,674	$	546	$	145	$	808
December 31, 2022	11,422		2,601		3,534		520		135		801

The projected benefit obligations for the qualified and non-qualified pension plans at December 31, 2023 are shown in the following table. All pension plan assets are related to the qualified pension plan.


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Projected benefit obligations:
Qualified pension plan	$	12,540	$	2,959	$	3,865	$	569	$	154	$	822
Non-qualified pension plan	713		117		145		29		22		60

Changes in projected benefit obligations and fair value of plan assets

Changes in the projected benefit obligations and the fair value of plan assets during the plan years ended December 31, 2023 and 2022 were as follows:


	2023
	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Change in benefit obligation
Benefit obligation at beginning of year	$	12,602	$	2,906	$	3,851	$	569	$	163	$	868

Service cost	275		64		68		11		6		24
Interest cost	626		145		191		28		8		42

Benefits paid	(744)		(155)		(224)		(32)		(6)		(104)
Actuarial loss	493		116		123		23		6		52
Balance at end of year	13,252		3,076		4,009		599		177		882
Change in plan assets
Fair value of plan assets at beginning of year	14,218		3,427		4,456		649		178		1,002

Actual return on plan assets	1,092		260		331		50		12		79
Employer contributions	52		11		9		2		2		3
Benefits paid	(744)		(154)		(225)		(32)		(7)		(104)
Fair value of plan assets at end of year	14,618		3,544		4,571		669		185		980
Accrued asset	$	1,366	$	468	$	562	$	70	$	8	$	98


	2022
	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Change in benefit obligation
Benefit obligation at beginning of year	$	16,382	$	3,806	$	5,012	$	743	$	222	$	1,134

Service cost	412		99		103		17		9		34
Interest cost	408		96		123		18		6		28
Benefits paid	(692)		(144)		(226)		(30)		(5)		(75)
Actuarial gain	(3,908)		(951)		(1,161)		(179)		(69)		(253)
Balance at end of year	12,602		2,906		3,851		569		163		868
Change in plan assets
Fair value of plan assets at beginning of year	17,225		4,141		5,415		786		213		1,241

Actual loss on plan assets	(2,376)		(579)		(753)		(110)		(31)		(167)
Employer contributions	61		9		20		3		1		3
Benefits paid	(692)		(144)		(226)		(30)		(5)		(75)
Fair value of plan assets at end of year	14,218		3,427		4,456		649		178		1,002
Accrued asset	$	1,616	$	521	$	605	$	80	$	15	$	134

Amounts recognized in balance sheets

Amounts recognized in the balance sheets at December 31, 2023 and 2022 related to the Registrants' pension plans consist of the following:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
December 31, 2023:
Prepaid pension costs(a)	$	2,079	$	585	$	706	$	99	$	31	$	158
Other regulatory assets, deferred(b)	2,960		821		1,051		152		—		143

Other current liabilities	(64)		(11)		(13)		(2)		(2)		(3)
Employee benefit obligations(c)	(649)		(106)		(131)		(27)		(21)		(58)
Other regulatory liabilities, deferred	(47)		—		—		—		—		—
AOCI	79		—		—		—		20		(45)

December 31, 2022:
Prepaid pension costs(a)	$	2,290	$	629	$	738	$	108	$	37	$	183
Other regulatory assets, deferred(b)	2,455		679		887		123		—		111

Other current liabilities	(56)		(10)		(12)		(2)		(2)		(3)
Employee benefit obligations(c)	(618)		(98)		(121)		(26)		(20)		(42)
Other regulatory liabilities, deferred	(85)		—		—		—		—		—
AOCI	24		—		—		—		11		(75)

(a)Included in prepaid pension and other postretirement benefit costs on Alabama Power's balance sheet and other deferred charges and assets on Southern Power's consolidated balance sheet.

(b)Amounts for Southern Company exclude regulatory assets of $173 million and $190 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' pension plans prior to its acquisition by Southern Company.

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

Presented below are the amounts included in regulatory assets at December 31, 2023 and 2022 related to the portion of the defined benefit pension plan attributable to Southern Company, the traditional electric operating companies, and Southern Company Gas that had not yet been recognized in net periodic pension cost.


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Company Gas
	(in millions)
Balance at December 31, 2023
Regulatory assets:
Prior service cost	$	9	$	4	$	6	$	1	$	(7)
Net loss	2,904		817		1,045		151		100
Regulatory amortization	—		—		—		—		50
Total regulatory assets(*)	$	2,913	$	821	$	1,051	$	152	$	143

Balance at December 31, 2022
Regulatory assets:
Prior service cost	$	10	$	4	$	7	$	1	$	(9)
Net loss	2,361		675		880		122		66
Regulatory amortization	—		—		—		—		54
Total regulatory assets(*)	$	2,371	$	679	$	887	$	123	$	111

(*)Amounts for Southern Company exclude regulatory assets of $173 million and $190 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' pension plans prior to its acquisition by Southern Company.

Amounts recognized in the balance sheets at December 31, 2023 and 2022 related to the Registrants' other postretirement benefit plans consist of the following:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
December 31, 2023:
Prepaid other postretirement benefit costs(a)	$	—	$	74	$	—	$	—	$	—	$	—
Other regulatory assets, deferred(b)	23		—		11		—		—		—
Other current liabilities	(6)		—		—		—		(1)		—
Employee benefit obligations(c)	(285)		—		(79)		(32)		(8)		(44)
Other regulatory liabilities, deferred	(231)		(48)		(85)		(10)		—		(68)
AOCI	(9)		—		—		—		1		(10)

December 31, 2022:
Prepaid other postretirement benefit costs(a)	$	—	$	28	$	—	$	—	$	—	$	—
Other regulatory assets, deferred(b)	34		—		19		—		—		—
Other current liabilities	(6)		—		—		—		(1)		—
Employee benefit obligations(c)	(437)		—		(146)		(35)		(8)		(66)
Other regulatory liabilities, deferred	(170)		(21)		(58)		(9)		—		(58)
AOCI	(4)		—		—		—		—		(2)

(a)Included in prepaid pension and other postretirement benefit costs on Alabama Power's balance sheet.

(b)Amounts for Southern Company exclude regulatory assets of $24 million and $32 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' other postretirement benefit plans prior to its acquisition by Southern Company.

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

Presented below are the amounts included in net regulatory assets (liabilities) at December 31, 2023 and 2022 related to the other postretirement benefit plans of Southern Company, the traditional electric operating companies, and Southern Company Gas that had not yet been recognized in net periodic other postretirement benefit cost.


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Company Gas
	(in millions)
Balance at December 31, 2023:
Regulatory assets (liabilities):
Prior service cost	$	13	$	4	$	5	$	1	$	—
Net gain	(216)		(52)		(79)		(11)		(64)
Regulatory amortization	—		—		—		—		(4)
Total regulatory assets (liabilities)(*)	$	(203)	$	(48)	$	(74)	$	(10)	$	(68)

Balance at December 31, 2022:
Regulatory assets (liabilities):
Prior service cost	$	14	$	4	$	6	$	1	$	1
Net gain	(150)		(25)		(45)		(10)		(64)
Regulatory amortization	—		—		—		—		5
Total regulatory assets (liabilities)(*)	$	(136)	$	(21)	$	(39)	$	(9)	$	(58)

(*)Amounts for Southern Company exclude regulatory assets of $24 million and $32 million at December 31, 2023 and 2022, respectively, associated with unamortized amounts in Southern Company Gas' other postretirement benefit plans prior to its acquisition by Southern Company.

Changes in balances of regulatory assets and regulatory liabilities related to defined benefit pension plans

The changes in the balance of regulatory assets related to the portion of the defined benefit pension plan attributable to Southern Company, the traditional electric operating companies, and Southern Company Gas for the years ended December 31, 2023 and 2022 are presented in the following table:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Company Gas
	(in millions)
Regulatory assets (liabilities):(*)
Balance at December 31, 2021	$	2,801	$	809	$	971	$	146	$	91
Net (gain) loss	(183)		(67)		(9)		(12)		27


Reclassification adjustments:
Amortization of prior service costs	(1)		(1)		(1)		—		2
Amortization of net gain (loss)	(246)		(62)		(74)		(11)		1
Amortization of regulatory assets(*)	—		—		—		—		(10)
Total reclassification adjustments	(247)		(63)		(75)		(11)		(7)
Total change	(430)		(130)		(84)		(23)		20
Balance at December 31, 2022	$	2,371	$	679	$	887	$	123	$	111
Net loss	576		153		178		31		34


Reclassification adjustments:
Amortization of prior service costs	(1)		(1)		(1)		—		2
Amortization of net loss	(33)		(10)		(13)		(2)		—
Amortization of regulatory assets(*)	—		—		—		—		(4)
Total reclassification adjustments	(34)		(11)		(14)		(2)		(2)
Total change	542		142		164		29		32
Balance at December 31, 2023	$	2,913	$	821	$	1,051	$	152	$	143

The changes in the balance of net regulatory assets (liabilities) related to the other postretirement benefit plans for the plan years ended December 31, 2023 and 2022 are presented in the following table:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Company Gas
	(in millions)
Net regulatory assets (liabilities):(*)
Balance at December 31, 2021	$	(74)	$	(62)	$	(10)	$	1	$	(34)
Net (gain) loss	(64)		41		(27)		(10)		(13)


Reclassification adjustments:
Amortization of prior service costs	1		—		—		—		—
Amortization of net gain (loss)	1		—		(2)		—		—
Amortization of regulatory assets(*)	—		—		—		—		(11)
Total reclassification adjustments	2		—		(2)		—		(11)
Total change	(62)		41		(29)		(10)		(24)
Balance at December 31, 2022	$	(136)	$	(21)	$	(39)	$	(9)	$	(58)
Net gain	(77)		(30)		(38)		(1)		—


Reclassification adjustments:
Amortization of prior service costs	(1)		—		(1)		—		—
Amortization of net gain	6		3		4		—		—
Amortization of regulatory assets(*)	—		—		—		—		(10)
Total reclassification adjustments	5		3		3		—		(10)
Total change	(72)		(27)		(35)		(1)		(10)
Balance at December 31, 2023	$	(208)	$	(48)	$	(74)	$	(10)	$	(68)

Amounts included in AOCI related to defined benefit pension plans

Presented below are the amounts included in AOCI at December 31, 2023 and 2022 related to the portion of the defined benefit pension plan attributable to Southern Company, Southern Power, and Southern Company Gas that had not yet been recognized in net periodic pension cost.


	Southern Company		Southern Power		Southern Company Gas
	(in millions)
Balance at December 31, 2023
AOCI:
Prior service cost	$	(1)	$	—	$	(2)
Net (gain) loss	80		20		(43)
Total AOCI	$	79	$	20	$	(45)

Balance at December 31, 2022
AOCI:
Prior service cost	$	(2)	$	—	$	(3)
Net (gain) loss	26		11		(72)
Total AOCI	$	24	$	11	$	(75)

Presented below are the amounts included in AOCI at December 31, 2023 and 2022 related to the other postretirement benefit plans of Southern Company, Southern Power, and Southern Company Gas that had not yet been recognized in net periodic other postretirement benefit cost.


	Southern Company		Southern Power		Southern Company Gas
	(in millions)
Balance at December 31, 2023
AOCI:
Prior service cost	$	1	$	—	$	—
Net (gain) loss	(10)		1		(10)
Total AOCI	$	(9)	$	1	$	(10)

Balance at December 31, 2022
AOCI:
Prior service cost	$	1	$	—	$	—
Net (gain) loss	(5)		—		(2)
Total AOCI	$	(4)	$	—	$	(2)

Components of OCI related to defined benefit pension plan

The components of OCI related to the portion of the defined benefit pension plan attributable to Southern Company, Southern Power, and Southern Company Gas for the years ended December 31, 2023 and 2022 are presented in the following table:


	Southern Company		Southern Power		Southern Company Gas
	(in millions)
AOCI:
Balance at December 31, 2021	$	100	$	35	$	(45)
Net gain	(82)		(22)		(30)


Reclassification adjustments:

Amortization of net gain (loss)	6		(2)		—

Total change	(76)		(24)		(30)
Balance at December 31, 2022	$	24	$	11	$	(75)
Net loss	62		9		29

Reclassification adjustments:
Amortization of prior service costs	1		—		1
Amortization of net loss	(8)		—		—
Total reclassification adjustments	(7)		—		1
Total change	55		9		30
Balance at December 31, 2023	$	79	$	20	$	(45)

The components of OCI related to the other postretirement benefit plans for the plan years ended December 31, 2023 and 2022 are presented in the following table:


	Southern Company		Southern Power		Southern Company Gas
	(in millions)
AOCI:
Balance at December 31, 2021	$	—	$	2	$	(5)
Net gain	(3)		(2)		—

Reclassification adjustments:

Amortization of net gain (loss)	(1)		—		3

Total change	(4)		(2)		3
Balance at December 31, 2022	$	(4)	$	—	$	(2)
Net (gain) loss	(12)		1		—

Reclassification adjustments:

Amortization of net gain (loss)	7		—		(8)

Total change	(5)		1		(8)
Balance at December 31, 2023	$	(9)	$	1	$	(10)

Components of net periodic benefit cost

Components of net periodic pension cost for the Registrants were as follows:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
2023
Service cost	$	275	$	64	$	68	$	11	$	6	$	24
Interest cost	626		145		191		28		8		42
Expected return on plan assets	(1,229)		(297)		(385)		(56)		(15)		(85)
Recognized net (gain) loss	32		9		13		2		—		(5)
Net amortization	—		1		1		—		—		15
Prior service cost	—		—		—		—		—		(3)
Net periodic pension cost (income)	$	(296)	$	(78)	$	(112)	$	(15)	$	(1)	$	(12)

2022
Service cost	$	412	$	99	$	103	$	17	$	9	$	34
Interest cost	408		96		123		18		6		28
Expected return on plan assets	(1,265)		(306)		(399)		(57)		(15)		(91)
Recognized net loss	240		62		75		11		2		8
Net amortization	—		1		1		—		—		15
Prior service cost	—		—		—		—		—		(3)
Net periodic pension cost (income)	$	(205)	$	(48)	$	(97)	$	(11)	$	2	$	(9)

2021
Service cost	$	434	$	102	$	112	$	18	$	10	$	37
Interest cost	346		82		104		16		5		24
Expected return on plan assets	(1,191)		(287)		(375)		(55)		(14)		(86)
Recognized net loss	314		82		100		15		3		13
Net amortization	1		1		1		—		—		15
Prior service cost	—		—		—		—		—		(3)
Net periodic pension cost (income)	$	(96)	$	(20)	$	(58)	$	(6)	$	4	$	—

Components of the other postretirement benefit plans' net periodic cost for the Registrants were as follows:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
2023
Service cost	$	15	$	4	$	4	$	1	$	—	$	1
Interest cost	70		17		25		3		—		9
Expected return on plan assets	(83)		(33)		(29)		(3)		1		(10)
Net amortization	(11)		(3)		(3)		—		—		6
Net periodic postretirement benefit cost (income)	$	(9)	$	(15)	$	(3)	$	1	$	1	$	6

2022
Service cost	$	23	$	6	$	6	$	1	$	—	$	1
Interest cost	42		10		15		2		—		5
Expected return on plan assets	(80)		(32)		(28)		(2)		1		(9)
Net amortization	(1)		—		2		—		—		6
Net periodic postretirement benefit cost (income)	$	(16)	$	(16)	$	(5)	$	1	$	1	$	3

2021
Service cost	$	24	$	6	$	7	$	1	$	—	$	2
Interest cost	35		9		12		1		—		4
Expected return on plan assets	(76)		(30)		(26)		(1)		1		(10)
Net amortization	2		—		2		—		—		6
Net periodic postretirement benefit cost (income)	$	(15)	$	(15)	$	(5)	$	1	$	1	$	2

Estimated pension benefit payments

At December 31, 2023, estimated benefit payments were as follows:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Benefit Payments:
2024	$	748	$	164	$	241	$	33	$	7	$	57
2025	776		171		248		34		7		59
2026	801		177		254		36		8		60
2027	822		182		257		37		8		62
2028	840		187		260		38		7		64
2029 to 2033	4,417		988		1,337		201		47		336


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Benefit payments:
2024	$	111	$	24	$	40	$	5	$	1	$	17
2025	109		24		39		5		1		17
2026	108		24		38		5		1		16
2027	108		24		38		5		1		16
2028	108		25		38		4		1		15
2029 to 2033	523		123		188		21		1		64

Changes in the APBO and the fair value of plan assets

Changes in the APBO and the fair value of the Registrants' plan assets during the plan years ended December 31, 2023 and 2022 were as follows:


	2023
	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Change in benefit obligation
Benefit obligation at beginning of year	$	1,441	$	344	$	514	$	59	$	9	$	179

Service cost	15		4		4		1		—		1
Interest cost	70		17		25		3		—		9
Benefits paid	(107)		(24)		(36)		(4)		(1)		(18)
Actuarial (gain) loss	(33)		(12)		(18)		(2)		1		1

Balance at end of year	1,386		329		489		57		9		172
Change in plan assets
Fair value of plan assets at beginning of year	998		372		368		24		—		113

Actual return on plan assets	131		52		51		2		—		19
Employer contributions	73		3		27		3		1		14
Benefits paid	(107)		(24)		(36)		(4)		(1)		(18)
Fair value of plan assets at end of year	1,095		403		410		25		—		128
Accrued asset (liability)	$	(291)	$	74	$	(79)	$	(32)	$	(9)	$	(44)


	2022
	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
Change in benefit obligation
Benefit obligation at beginning of year	$	1,849	$	440	$	656	$	76	$	11	$	237

Service cost	23		6		6		1		—		1
Interest cost	42		10		15		2		—		5
Benefits paid	(109)		(23)		(38)		(4)		(1)		(18)
Actuarial gain	(365)		(89)		(125)		(16)		(1)		(46)
Retiree drug subsidy	1		—		—		—		—		—
Balance at end of year	1,441		344		514		59		9		179
Change in plan assets
Fair value of plan assets at beginning of year	1,251		489		450		29		—		143

Actual loss on plan assets	(218)		(98)		(71)		(4)		—		(25)
Employer contributions	73		4		27		3		1		13
Benefits paid	(108)		(23)		(38)		(4)		(1)		(18)
Fair value of plan assets at end of year	998		372		368		24		—		113
Accrued asset (liability)	$	(443)	$	28	$	(146)	$	(35)	$	(9)	$	(66)

Summary of investment strategies and benefit plan asset fair values

A description of the major asset classes that the pension and other postretirement benefit plans are comprised of, along with the valuation methods used for fair value measurement, is provided below:


Description			Valuation Methodology
Domestic equity: A mix of large and small capitalization stocks with generally an equal distribution of value and growth attributes, managed both actively and through passive index approaches. International equity: A mix of large and small capitalization growth and value stocks with developed and emerging markets exposure, managed both actively and through fundamental indexing approaches.			Domestic and international equities such as common stocks, American depositary receipts, and real estate investment trusts that trade on public exchanges are classified as Level 1 investments and are valued at the closing price in the active market. Equity funds with unpublished prices that are comprised of publicly traded securities (such as commingled/pooled funds) are also valued at the closing price in the active market, but are classified as Level 2.
Fixed income: A mix of domestic and international bonds.			Investments in fixed income securities, including fixed income pooled funds, are generally classified as Level 2 investments and are valued based on prices reported in the market place. Additionally, the value of fixed income securities takes into consideration certain items such as broker quotes, spreads, yield curves, interest rates, and discount rates that apply to the term of a specific instrument.
Trust-owned life insurance (TOLI): Investments of taxable trusts aimed at minimizing the impact of taxes on the portfolio.			Investments in TOLI policies are classified as Level 2 investments and are valued based on the underlying investments held in the policy's separate accounts. The underlying assets are equity and fixed income pooled funds that are comprised of Level 1 and Level 2 securities.
Real estate: Investments in equity or debt of real properties and in publicly traded real estate securities. Special situations: Investments in opportunistic strategies with the objective of diversifying and enhancing returns and exploiting short-term inefficiencies, as well as investments in promising new strategies of a longer-term nature. Private equity: Investments in private or public securities typically through privately-negotiated and/or structured transactions, including leveraged buyouts, venture capital, and distressed debt. Private credit: Investments focused on debt instruments, of which returns are driven by income rather than capital appreciation. Infrastructure: Investments in real assets, typically with long-term, predictable, and stable cash flows and a meaningful income component.			Investments in real estate, special situations, private equity, private credit, and infrastructure are typically invested in private partnerships and/or other pooled vehicles (Funds) which are generally classified as Net Asset Value as a Practical Expedient, since the Funds and underlying assets are not publicly traded and/or often have liquidity restrictions. The managers of the Funds value the assets using various inputs and techniques depending on the nature of the underlying investments. Techniques may include purchase multiples for comparable transactions, comparable public company trading multiples, discounted cash flow analysis, prevailing market capitalization rates, recent sales of comparable investments, and independent third-party appraisals. The total market value of each of the Funds is determined by aggregating the value of the underlying assets less liabilities.

Fair values of plan assets

The fair values, and actual allocations relative to the target allocations, of the Southern Company system's pension plans at December 31, 2023 and 2022 are presented below.


	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				Target Allocation		Actual Allocation
At December 31, 2023:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Company
Assets:
Equity:											41	%	40	%
Domestic equity	$	1,959	$	771	$	—	$	—	$	2,730
International equity	1,947		1,052		—		—		2,999
Fixed income:											30		32
U.S. Treasury, government, and agency bonds	—		1,973		—		—		1,973
Mortgage- and asset-backed securities	—		44		—		—		44
Corporate bonds	—		1,724		—		—		1,724
Pooled funds	—		777		—		—		777
Cash equivalents and other	371		58		—		—		429
Real estate investments	369		—		—		1,684		2,053		12		14
Special situations	—		—		—		245		245		3		2
Private equity	—		—		—		1,761		1,761		9		12
Private credit	—		—		—		25		25		3		—
Infrastructure	—		—		—		—		—		2		—
Total	$	4,646	$	6,399	$	—	$	3,715	$	14,760	100	%	100	%




Alabama Power
Assets:
Equity:											41	%	40	%
Domestic equity	$	476	$	187	$	—	$	—	$	663
International equity	472		255		—		—		727
Fixed income:											30		32
U.S. Treasury, government, and agency bonds	—		479		—		—		479
Mortgage- and asset-backed securities	—		11		—		—		11
Corporate bonds	—		418		—		—		418
Pooled funds	—		188		—		—		188
Cash equivalents and other	90		14		—		—		104
Real estate investments	89		—		—		408		497		12		14
Special situations	—		—		—		59		59		3		2
Private equity	—		—		—		427		427		9		12
Private credit	—		—		—		6		6		3		—
Infrastructure	—		—		—		—		—		2		—
Total	$	1,127	$	1,552	$	—	$	900	$	3,579	100	%	100	%


	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				Target Allocation		Actual Allocation
At December 31, 2023:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Georgia Power
Assets:
Equity:											41	%	40	%
Domestic equity	$	611	$	241	$	—	$	—	$	852
International equity	609		329		—		—		938
Fixed income:											30		32
U.S. Treasury, government, and agency bonds	—		617		—		—		617
Mortgage- and asset-backed securities	—		14		—		—		14
Corporate bonds	—		539		—		—		539
Pooled funds	—		243		—		—		243
Cash equivalents and other	116		18		—		—		134
Real estate investments	115		—		—		527		642		12		14
Special situations	—		—		—		77		77		3		2
Private equity	—		—		—		551		551		9		12
Private credit	—		—		—		8		8		3		—
Infrastructure	—		—		—		—		—		2		—
Total	$	1,451	$	2,001	$	—	$	1,163	$	4,615	100	%	100	%




Mississippi Power
Assets:
Equity:											41	%	40	%
Domestic equity	$	89	$	35	$	—	$	—	$	124
International equity	89		48		—		—		137
Fixed income:											30		32
U.S. Treasury, government, and agency bonds	—		90		—		—		90
Mortgage- and asset-backed securities	—		2		—		—		2
Corporate bonds	—		79		—		—		79
Pooled funds	—		36		—		—		36
Cash equivalents and other	17		3		—		—		20
Real estate investments	17		—		—		77		94		12		14
Special situations	—		—		—		11		11		3		2
Private equity	—		—		—		81		81		9		12
Private credit	—		—		—		1		1		3		—
Infrastructure	—		—		—		—		—		2		—
Total	$	212	$	293	$	—	$	170	$	675	100	%	100	%


	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				Target Allocation		Actual Allocation
At December 31, 2023:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Power
Assets:
Equity:											41	%	40	%
Domestic equity	$	24	$	10	$	—	$	—	$	34
International equity	25		13		—		—		38
Fixed income:											30		32
U.S. Treasury, government, and agency bonds	—		25		—		—		25
Mortgage- and asset-backed securities	—		1		—		—		1
Corporate bonds	—		22		—		—		22
Pooled funds	—		10		—		—		10
Cash equivalents and other	5		1		—		—		6
Real estate investments	5		—		—		21		26		12		14
Special situations	—		—		—		3		3		3		2
Private equity	—		—		—		22		22		9		12
Private credit	—		—		—		—		—		3		—
Infrastructure	—		—		—		—		—		2		—
Total	$	59	$	82	$	—	$	46	$	187	100%		100	%

Southern Company Gas
Assets:
Equity:											41	%	40	%
Domestic equity	$	130	$	52	$	—	$	—	$	182
International equity	130		71		—		—		201
Fixed income:											30		32
U.S. Treasury, government, and agency bonds	—		132		—		—		132
Mortgage- and asset-backed securities	—		3		—		—		3
Corporate bonds	—		116		—		—		116
Pooled funds	—		52		—		—		52
Cash equivalents and other	25		4		—		—		29
Real estate investments	25		—		—		113		138		12		14
Special situations	—		—		—		16		16		3		2
Private equity	—		—		—		118		118		9		12
Private credit	—		—		—		2		2		3		—
Infrastructure	—		—		—		—		—		2		—
Total	$	310	$	430	$	—	$	249	$	989	100	%	100	%


	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				Target Allocation		Actual Allocation
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Company
Assets:
Equity:											45	%	43	%
Domestic equity	$	2,078	$	691	$	—	$	—	$	2,769
International equity	2,166		1,090		—		—		3,256
Fixed income:											30		28
U.S. Treasury, government, and agency bonds	—		1,469		—		—		1,469
Mortgage- and asset-backed securities	—		29		—		—		29
Corporate bonds	—		1,494		—		—		1,494
Pooled funds	—		607		—		—		607
Cash equivalents and other	399		7		—		—		406
Real estate investments	376		—		—		1,887		2,263		13		15
Special situations	—		—		—		187		187		3		2
Private equity	—		—		—		1,717		1,717		9		12
Total	$	5,019	$	5,387	$	—	$	3,791	$	14,197	100	%	100	%
Liabilities:
Derivatives	(4)		—		—		—		(4)
Total	$	5,015	$	5,387	$	—	$	3,791	$	14,193	100	%	100	%

Alabama Power
Assets:
Equity:											45	%	43	%
Domestic equity	$	500	$	167	$	—	$	—	$	667
International equity	522		263		—		—		785
Fixed income:											30		28
U.S. Treasury, government, and agency bonds	—		354		—		—		354
Mortgage- and asset-backed securities	—		7		—		—		7
Corporate bonds	—		360		—		—		360
Pooled funds	—		146		—		—		146
Cash equivalents and other	96		2		—		—		98
Real estate investments	91		—		—		455		546		13		15
Special situations	—		—		—		45		45		3		2
Private equity	—		—		—		414		414		9		12
Total	$	1,209	$	1,299	$	—	$	914	$	3,422	100	%	100	%
Liabilities:
Derivatives	(1)		—		—		—		(1)
Total	$	1,208	$	1,299	$	—	$	914	$	3,421	100	%	100	%


	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				Target Allocation		Actual Allocation
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Georgia Power
Assets:
Equity:											45	%	43	%
Domestic equity	$	651	$	217	$	—	$	—	$	868
International equity	678		342		—		—		1,020
Fixed income:											30		28
U.S. Treasury, government, and agency bonds	—		460		—		—		460
Mortgage- and asset-backed securities	—		9		—		—		9
Corporate bonds	—		468		—		—		468
Pooled funds	—		190		—		—		190
Cash equivalents and other	125		2		—		—		127
Real estate investments	118		—		—		591		709		13		15
Special situations	—		—		—		59		59		3		2
Private equity	—		—		—		538		538		9		12
Total	$	1,572	$	1,688	$	—	$	1,188	$	4,448	100	%	100	%
Liabilities:
Derivatives	(1)		—		—		—		(1)
Total	$	1,571	$	1,688	$	—	$	1,188	$	4,447	100	%	100	%

Mississippi Power
Assets:
Equity:											45	%	43	%
Domestic equity	$	95	$	32	$	—	$	—	$	127
International equity	99		50		—		—		149
Fixed income:											30		28
U.S. Treasury, government, and agency bonds	—		67		—		—		67
Mortgage- and asset-backed securities	—		1		—		—		1
Corporate bonds	—		68		—		—		68
Pooled funds	—		28		—		—		28
Cash equivalents and other	18		—		—		—		18
Real estate investments	17		—		—		86		103		13		15
Special situations	—		—		—		9		9		3		2
Private equity	—		—		—		78		78		9		12
Total	$	229	$	246	$	—	$	173	$	648	100	%	100	%


	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				Target Allocation		Actual Allocation
At December 31, 2022:	(Level 1)		(Level 2)		(Level 3)		(NAV)		Total
	(in millions)
Southern Power
Assets:
Equity:											45	%	43	%
Domestic equity	$	25	$	9	$	—	$	—	$	34
International equity	27		14		—		—		41
Fixed income:											30		28
U.S. Treasury, government, and agency bonds	—		18		—		—		18
Corporate bonds	—		19		—		—		19
Pooled funds	—		8		—		—		8
Cash equivalents and other	5		—		—		—		5
Real estate investments	5		—		—		24		29		13		15
Special situations	—		—		—		2		2		3		2
Private equity	—		—		—		21		21		9		12
Total	$	62	$	68	$	—	$	47	$	177	100	%	100	%

Southern Company Gas
Assets:
Equity:											45	%	43	%
Domestic equity	$	146	$	49	$	—	$	—	$	195
International equity	152		77		—		—		229
Fixed income:											30		28
U.S. Treasury, government, and agency bonds	—		104		—		—		104
Mortgage- and asset-backed securities	—		2		—		—		2
Corporate bonds	—		105		—		—		105
Pooled funds	—		43		—		—		43
Cash equivalents and other	28		1		—		—		29
Real estate investments	27		—		—		133		160		13		15
Special situations	—		—		—		13		13		3		2
Private equity	—		—		—		121		121		9		12
Total	$	353	$	381	$	—	$	267	$	1,001	100	%	100	%

The fair values, and actual allocations relative to the target allocations, of the applicable Registrants' other postretirement benefit plan assets at December 31, 2023 and 2022 are presented below.


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Net Asset Value as a Practical Expedient		Total		Target Allocation		Actual Allocation
At December 31, 2023:	(Level 1)		(Level 2)		(NAV)
	(in millions)
Southern Company
Assets:
Equity:									60	%	61	%
Domestic equity	$	85	$	87	$	—	$	172
International equity	53		82		—		135
Fixed income:									30		28
U.S. Treasury, government, and agency bonds	—		57		—		57
Mortgage- and asset-backed securities	—		2		—		2
Corporate bonds	—		47		—		47
Pooled funds	—		92		—		92
Cash equivalents and other	21		2		—		23
Trust-owned life insurance	—		456		—		456
Real estate investments	11		—		46		57		4		6
Special situations	—		—		6		6		1		1
Private equity	—		—		48		48		3		4
Private credit	—		—		1		1		1		—
Infrastructure	—		—		—		—		1		—
Total	$	170	$	825	$	101	$	1,096	100	%	100	%

Alabama Power
Assets:
Equity:									67	%	66	%
Domestic equity	$	16	$	6	$	—	$	22
International equity	16		9		—		25
Fixed income:									23		23
U.S. Treasury, government, and agency bonds	—		16		—		16

Corporate bonds	—		14		—		14
Pooled funds	—		8		—		8
Cash equivalents and other	3		—		—		3
Trust-owned life insurance	—		280		—		280
Real estate investments	3		—		14		17		4		6
Special situations	—		—		2		2		1		1
Private equity	—		—		15		15		3		4
Private credit	—		—		—		—		1		—
Infrastructure	—		—		—		—		1		—
Total	$	38	$	333	$	31	$	402	100	%	100	%


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Net Asset Value as a Practical Expedient		Total		Target Allocation		Actual Allocation
At December 31, 2023:	(Level 1)		(Level 2)		(NAV)
	(in millions)
Georgia Power
Assets:
Equity:									58	%	57	%
Domestic equity	$	47	$	6	$	—	$	53
International equity	16		40		—		56
Fixed income:									35		35
U.S. Treasury, government, and agency bonds	—		16		—		16

Corporate bonds	—		14		—		14
Pooled funds	—		47		—		47
Cash equivalents and other	13		—		—		13
Trust-owned life insurance	—		176		—		176
Real estate investments	4		—		14		18		3		4
Special situations	—		—		2		2		1		1
Private equity	—		—		14		14		2		3
Private credit	—		—		—		—		1		—
Infrastructure	—		—		—		—		—		—
Total	$	80	$	299	$	30	$	409	100	%	100	%

Mississippi Power
Assets:
Equity:									34	%	33	%
Domestic equity	$	3	$	1	$	—	$	4
International equity	3		1		—		4
Fixed income:									43		44
U.S. Treasury, government, and agency bonds	—		7		—		7
Corporate bonds	—		2		—		2
Pooled funds	—		1		—		1
Cash equivalents and other	1		—		—		1

Real estate investments	1		—		2		3		10		11
Special situations	—		—		—		—		2		2
Private equity	—		—		2		2		7		10
Private credit	—		—		—		—		3		—
Infrastructure	—		—		—		—		1		—
Total	$	8	$	12	$	4	$	24	100	%	100	%


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Net Asset Value as a Practical Expedient		Total		Target Allocation		Actual Allocation
At December 31, 2023:	(Level 1)		(Level 2)		(NAV)
	(in millions)
Southern Company Gas
Assets:
Equity:									72	%	72	%
Domestic equity	$	2	$	67	$	—	$	69
International equity	2		22		—		24
Fixed income:									26		26
U.S. Treasury, government, and agency bonds	—		1		—		1

Corporate bonds	—		1		—		1
Pooled funds	—		29		—		29
Cash equivalents and other	1		—		—		1
Trust-owned life insurance	—		—		—		—
Real estate investments	—		—		1		1		1		1

Private equity	—		—		1		1		1		1


Total	$	5	$	120	$	2	$	127	100	%	100	%


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Net Asset Value as a Practical Expedient				Target Allocation		Actual Allocation
At December 31, 2022:	(Level 1)		(Level 2)		(NAV)		Total
	(in millions)
Southern Company
Assets:
Equity:									61	%	59	%
Domestic equity	$	85	$	74	$	—	$	159
International equity	58		79		—		137
Fixed income:									30		28
U.S. Treasury, government, and agency bonds	—		43		—		43
Mortgage- and asset-backed securities	—		1		—		1
Corporate bonds	—		40		—		40
Pooled funds	—		79		—		79
Cash equivalents and other	19		—		—		19
Trust-owned life insurance	—		406		—		406
Real estate investments	11		—		51		62		5		7
Special situations	—		—		6		6		1		1
Private equity	—		—		46		46		3		5
Total	$	173	$	722	$	103	$	998	100	%	100	%

Alabama Power
Assets:
Equity:									69	%	65	%
Domestic equity	$	17	$	6	$	—	$	23
International equity	18		9		—		27
Fixed income:									23		23
U.S. Treasury, government, and agency bonds	—		12		—		12

Corporate bonds	—		12		—		12
Pooled funds	—		7		—		7
Cash equivalents and other	3		—		—		3
Trust-owned life insurance	—		252		—		252
Real estate investments	3		—		16		19		4		7
Special situations	—		—		2		2		1		1
Private equity	—		—		14		14		3		4
Total	$	41	$	298	$	32	$	371	100	%	100	%


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Net Asset Value as a Practical Expedient				Target Allocation		Actual Allocation
At December 31, 2022:	(Level 1)		(Level 2)		(NAV)		Total
	(in millions)
Georgia Power
Assets:
Equity:									58	%	56	%
Domestic equity	$	46	$	6	$	—	$	52
International equity	17		39		—		56
Fixed income:									35		34
U.S. Treasury, government, and agency bonds	—		10		—		10

Corporate bonds	—		12		—		12
Pooled funds	—		40		—		40
Cash equivalents and other	9		—		—		9
Trust-owned life insurance	—		154		—		154
Real estate investments	4		—		15		19		4		5
Special situations	—		—		2		2		1		1
Private equity	—		—		14		14		2		4
Total	$	76	$	261	$	31	$	368	100	%	100	%

Mississippi Power
Assets:
Equity:									37	%	35	%
Domestic equity	$	3	$	1	$	—	$	4
International equity	3		2		—		5
Fixed income:									43		41
U.S. Treasury, government, and agency bonds	—		4		—		4

Corporate bonds	—		2		—		2
Pooled funds	—		1		—		1
Cash equivalents and other	2		—		—		2
Real estate investments	1		—		3		4		11		12
Special situations	—		—		—		—		2		2
Private equity	—		—		2		2		7		10
Total	$	9	$	10	$	5	$	24	100	%	100	%


	Fair Value Measurements Using
	Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Net Asset Value as a Practical Expedient				Target Allocation		Actual Allocation
At December 31, 2022:	(Level 1)		(Level 2)		(NAV)		Total
	(in millions)
Southern Company Gas
Assets:
Equity:									72	%	70	%
Domestic equity	$	2	$	56	$	—	$	58
International equity	2		20		—		22
Fixed income:									26		27
U.S. Treasury, government, and agency bonds	—		1		—		1

Corporate bonds	—		1		—		1
Pooled funds	—		27		—		27
Cash equivalents and other	1		—		—		1

Real estate investments	—		—		2		2		1		2

Private equity	—		—		1		1		1		1
Total	$	5	$	105	$	3	$	113	100	%	100	%

Total matching contributions

Total matching contributions made to the plans for 2023, 2022, and 2021 were as follows:


	Southern Company		Alabama Power		Georgia Power		Mississippi Power		Southern Power		Southern Company Gas
	(in millions)
2023	$	131	$	28	$	31	$	5	$	3	$	18
2022	124		26		29		5		3		17
2021	119		26		28		5		2		16