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REGULATORY MATTERS (Tables)
 12 Months Ended
Dec. 31, 2023
Regulated Operations [Abstract]  
Schedule of regulatory assets
Details of regulatory assets and (liabilities) reflected in the balance sheets at December 31, 2023 and 2022 are provided in the following tables:
Southern CompanyAlabama PowerGeorgia PowerMississippi PowerSouthern Company Gas
(in millions)
At December 31, 2023
AROs(a)(w)
$5,733 $1,936 $3,505 $247 $— 
Retiree benefit plans(b)(w)
3,011 815 976 140 146 
Remaining net book value of retired assets(c)
1,357 499 841 17 — 
Deferred income tax charges(d)
897 262 605 28 — 
Under recovered regulatory clause revenues(e)
413 381 — 12 20 
Fuel-hedging (realized and unrealized) losses(f)
270 100 121 49 — 
Deferred depreciation(g)
270 143 127 — — 
Environmental remediation(h)(w)
255 — 20 — 235 
Loss on reacquired debt(i)
238 35 197 5 1 
Vacation pay(j)(w)
217 83 107 11 16 
Software and cloud computing costs(k)
150 59 84 2 5 
Regulatory clauses(l)
140 112 — — 28 
Storm damage(m)
92 — 54 38 — 
Nuclear outage(n)
83 50 33 — — 
Long-term debt fair value adjustment(o)
60 — — — 60 
Qualifying repairs of natural gas distribution systems(p)
40 — — — 40 
Plant Daniel Units 3 and 4(q)
25 — — 25 — 
Kemper County energy facility assets, net(r)
7 — — 7 — 
Other regulatory assets(s)
182 39 33 18 93 
Deferred income tax credits(d)
(4,686)(1,506)(2,161)(241)(759)
Other cost of removal obligations(a)
(1,312)28 617 (186)(1,771)
Over recovered regulatory clause revenues(e)
(287)(3)(46)— (238)
Reliability reserves(t)
(179)(143)— (36)— 
Storm/property damage reserves(t)
(120)(76)— (44)— 
Customer refunds(u)
(19)(15)(4)— — 
Fuel-hedging (realized and unrealized) gains(f)
(6)(5)(1)— 
Other regulatory liabilities(v)
(308)(74)(18)(2)(101)
Total regulatory assets (liabilities), net$6,523 $2,720 $5,090 $90 $(2,225)
Southern CompanyAlabama PowerGeorgia PowerMississippi PowerSouthern Company Gas
(in millions)
At December 31, 2022
AROs(a)(w)
$6,096 $1,971 $3,829 $242 $— 
Retiree benefit plans(b)(w)
2,517 675 848 113 114 
Remaining net book value of retired assets(c)
1,543 562 962 19 — 
Under recovered regulatory clause revenues(e)
953 788 — 31 134 
Deferred income tax charges(d)
866 250 583 30 — 
Environmental remediation(h)(w)
294 — 25 — 269 
Loss on reacquired debt(i)
257 38 213 5 1 
Vacation pay(j)(w)
212 82 108 10 12 
Regulatory clauses(l)
142 142 — — — 
Software and cloud computing costs(k)
111 46 59 — 6 
Nuclear outage(n)
82 52 30 — — 
Long-term debt fair value adjustment(o)
69 — — — 69 
Fuel-hedging (realized and unrealized) losses(f)
60 15 45 — — 
Storm damage(m)
44 — — 44 — 
Plant Daniel Units 3 and 4(q)
27 — — 27 — 
Qualifying repairs of natural gas distribution systems(p)
26 — — — 26 
Kemper County energy facility assets, net(r)
20 — — 20 — 
Other regulatory assets(s)
171 36 27 16 92 
Deferred income tax credits(d)
(5,251)(1,925)(2,244)(269)(788)
Other cost of removal obligations(a)
(1,430)11 462 (196)(1,707)
Storm/property damage reserves(t)
(216)(97)(83)(36)— 
Reliability reserves(t)
(191)(166)— (25)— 
Customer refunds(u)
(183)(62)(121)— — 
Fuel-hedging (realized and unrealized) gains(f)
(83)(38)(21)(24)— 
Over recovered regulatory clause revenues(e)
(64)— (38)— (26)
Other regulatory liabilities(v)
(239)(40)(21)(3)(93)
Total regulatory assets (liabilities), net$5,833 $2,340 $4,663 $4 $(1,891)
Unless otherwise noted, the following recovery and amortization periods for these regulatory assets and (liabilities) have been approved by the respective state PSC or regulatory agency:
(a)AROs and other cost of removal obligations generally are recorded over the related property lives, which may range up to 64 years for Alabama Power, 56 years for Georgia Power, 55 years for Mississippi Power, and 85 years for Southern Company Gas. AROs and cost of removal obligations are settled and trued up following completion of the related activities. Alabama Power is recovering CCR ARO expenditures over a 38-year period ending in 2054 through Rate CNP Compliance. Effective January 1, 2023, Georgia Power is recovering CCR ARO expenditures over four-year periods through its ECCR tariff. Prior to 2023, expenditures were recovered over three-year periods. See "Georgia Power – Rate Plans" herein and Note 6 for additional information.
(b)Recovered and amortized over the average remaining service period, which may range up to 13 years for Alabama Power and Mississippi Power and up to 14 years for Georgia Power and Southern Company Gas. Southern Company's balances also include amounts at SCS and Southern Nuclear that are allocated to the applicable regulated utilities. See Note 11 for additional information.
(c)Alabama Power: Primarily represents the net book value of Plant Gorgas Unit 10 ($451 million at December 31, 2023) being amortized over 14 years (through 2037) and Plant Barry Unit 4 ($39 million at December 31, 2023) being amortized over 11 years (through 2034). See "Alabama Power – Environmental Accounting Order" herein for additional information.
Georgia Power: Net book values of Plant Wansley Units 1 and 2, Plant Hammond Units 1 through 4, and Plant Branch Unit 4 (totaling $488 million, $339 million, and $8 million, respectively, at December 31, 2023) are being amortized over remaining periods between one and 12 years (between 2024 and 2035). Balance also includes unusable materials and supplies inventories, for which the Georgia PSC will determine a recovery period in a future base rate case.
Mississippi Power: Represents net book value of certain environmental compliance assets at Plant Watson and Plant Greene County. The retail portion is being amortized over a 10-year period through 2030 and the wholesale portion is being amortized over a 14-year period through 2035. See "Mississippi Power – Environmental Compliance Overview Plan" herein for additional information.
(d)Deferred income tax charges are recovered and deferred income tax credits are primarily amortized over the related property lives, which may range up to 64 years for Alabama Power, 56 years for Georgia Power, 55 years for Mississippi Power, and 85 years for Southern Company Gas. See Note 10 for additional information. As a result of the Tax Reform Legislation, these accounts include certain deferred income tax assets and liabilities not subject to normalization, as described further below:
Alabama Power: Related amounts at December 31, 2023 include excess federal deferred income tax liabilities that are available for the benefit of customers in 2024 and/or 2025, as discussed under "Alabama Power – Excess Accumulated Deferred Income Tax Accounting Order" herein. Remaining amounts are being recovered and amortized ratably over the related property lives.
Georgia Power: Related amounts include $145 million of deferred income tax assets related to construction costs for Plant Vogtle Units 3 and 4 to be recovered over a 10-year period beginning the month after Unit 4 achieves commercial operation. See "Georgia Power – Nuclear Construction – Regulatory Matters" herein for additional information on recovery of costs related to Plant Vogtle Units 3 and 4.
Mississippi Power: Related amounts include retail deferred income tax liabilities ($11 million at December 31, 2023) that are expected to be fully amortized through 2024.
Southern Company Gas: Related amounts include deferred income tax liabilities ($1 million at December 31, 2023) being amortized through 2024. See "Southern Company Gas – Rate Proceedings" herein for additional information.
(e)Alabama Power: Balances are recorded monthly and expected to be recovered over periods of up to seven years, with the majority expected to be recovered within one year. See "Alabama Power – Rate CNP PPA," " – Rate CNP Compliance," and " – Rate ECR" herein for additional information.
Georgia Power: Balances are recorded monthly and expected to be recovered or returned within two years. See "Georgia Power – Rate Plans" herein for additional information.
Mississippi Power: At December 31, 2023, $12 million is expected to be recovered through various rate recovery mechanisms over a period to be determined in future rate filings. See "Mississippi Power – Ad Valorem Tax Adjustment" herein for additional information.
Southern Company Gas: Balances are recorded and recovered or amortized over periods generally not exceeding five years. In addition to natural gas cost recovery mechanisms, the natural gas distribution utilities have various other cost recovery mechanisms for the recovery of costs, including those related to infrastructure replacement programs.
(f)Fuel-hedging assets and liabilities are recorded over the life of the underlying hedged purchase contracts. Upon final settlement, actual costs incurred are recovered through the applicable traditional electric operating company's fuel cost recovery mechanism. Purchase contracts generally do not exceed three and a half years for Alabama Power, three years for Georgia Power, and four years for Mississippi Power.
(g)Alabama Power: Represents deferred depreciation expense for Plant Barry Unit 5 ($57 million at December 31, 2023) and Plant Barry common coal assets ($24 million at December 31, 2023) to be amortized until 2036 beginning when Plant Barry Unit 5 is retired and Plant Gaston Unit 5 coal assets ($62 million at December 31, 2023) to be amortized until 2039 beginning when the assets are retired.
Georgia Power: Represents deferred depreciation expense for Plant Scherer Units 1 through 3 ($70 million at December 31, 2023) to be amortized over six years beginning in 2029 and Plant Bowen Units 1 and 2 ($40 million at December 31, 2023) to be amortized over four years beginning in 2031, both as approved under Georgia Power's 2022 ARP, and Plant Vogtle Unit 3 and common facilities ($17 million at December 31, 2023) to be amortized over a 10-year period beginning the month after Plant Vogtle Unit 4 achieves commercial operation. See "Georgia Power – Nuclear Construction – Regulatory Matters" herein for additional information on recovery of costs related to Plant Vogtle Units 3 and 4.
(h)Effective January 1, 2023, Georgia Power is recovering $5 million annually for environmental remediation under the 2022 ARP. Southern Company Gas' costs are recovered through environmental cost recovery mechanisms when the remediation work is performed. See Note 3 under "Environmental Remediation" for additional information.
(i)Recovered over either the remaining life of the original issue or, if refinanced, over the remaining life of the new issue. At December 31, 2023, the remaining amortization periods do not exceed 24 years for Alabama Power, 29 years for Georgia Power, 18 years for Mississippi Power, and four years for Southern Company Gas.
(j)Recorded as earned by employees and recovered as paid, generally within one year. Includes both vacation and banked holiday pay, if applicable.
(k)Represents certain deferred operations and maintenance costs associated with software and cloud computing projects. For Alabama Power, costs are amortized ratably over the life of the related software, which ranges up to 10 years (through 2034). See "Alabama Power – Software Accounting Order" herein for additional information. For Georgia Power, costs incurred through 2022 are being amortized over five years (through 2027) and the recovery period for costs incurred after 2022 will be determined in its next base rate case. For Mississippi Power, the recovery period will be determined in Mississippi Power's annual PEP filing process. For Southern Company Gas, costs are being amortized ratably over the life of the related software, which ranges up to 10 years (through 2034).
(l)Alabama Power: Effective January 1, 2023, balance is being amortized through Rate RSE over a five-year period ending in 2027.
Southern Company Gas: Represents amounts related to Nicor Gas' volume balancing adjustment rider expected to be recovered over a period of less than two years.
(m)See "Georgia Power – Storm Damage Recovery" herein and Note 1 under "Storm Damage and Reliability Reserves" for additional information. Mississippi Power's balance represents deferred storm costs associated with Hurricanes Ida and Zeta being recovered through PEP over a seven-year period through 2029.
(n)Nuclear outage costs are deferred to a regulatory asset when incurred and amortized over a subsequent period of 18 months for Alabama Power and up to 24 months for Georgia Power. See Note 5 for additional information.
(o)Recovered over the remaining lives of the original debt issuances at acquisition, which range up to 15 years at December 31, 2023.
(p)Represents deferred costs of certain repairs at Atlanta Gas Light being amortized over 20 years.
(q)Represents the difference between Mississippi Power's revenue requirement for Plant Daniel Units 3 and 4 under purchase accounting and operating lease accounting. At December 31, 2023, consists of the $17 million retail portion being amortized through 2039 over the remaining life of the related property and the $8 million wholesale portion being amortized through 2035.
(r)At December 31, 2023, includes $9 million of regulatory assets (wholesale) expected to be fully amortized by 2035 and $2 million of regulatory liabilities (retail) expected to be fully amortized by 2024.
(s)Comprised of numerous immaterial components with remaining amortization periods at December 31, 2023 generally not exceeding 20 years for Alabama Power, 10 years for Georgia Power, 14 years for Mississippi Power, and 15 years for Southern Company Gas.
(t)Utilized as related expenses are incurred. See "Alabama Power – Rate NDR" and " – Reliability Reserve Accounting Order," "Georgia Power – Storm Damage Recovery," and "Mississippi Power – System Restoration Rider" and " – Reliability Reserve Accounting Order" herein and Note 1 under "Storm Damage and Reliability Reserves" for additional information.
(u)Primarily includes approximately $15 million and $62 million at December 31, 2023 and 2022, respectively, for Alabama Power and $119 million at December 31, 2022 for Georgia Power as a result of each company exceeding its allowed retail return range. Georgia Power's balances also include immaterial amounts related to refunds for transmission service customers. See "Alabama Power – Rate RSE" and "Georgia Power – Rate Plans" herein for additional information.
(v)Comprised of numerous immaterial components with remaining amortization periods at December 31, 2023 generally not exceeding 11 years for Alabama Power, nine years for Georgia Power, four years for Mississippi Power, and 20 years for Southern Company Gas.
(w)Generally not earning a return as they are excluded from rate base or are offset in rate base by a corresponding asset or liability.
The following table illustrates Southern Company Gas' authorized ratemaking amounts that are not recognized on its balance sheets. These amounts are primarily comprised of an allowed equity rate of return on assets associated with certain regulatory infrastructure programs. These amounts will be recognized as revenues in Southern Company Gas' financial statements in the periods they are billable to customers, the majority of which will be recovered by 2025.
December 31, 2023December 31, 2022
(in millions)
Atlanta Gas Light$23 $35 
Virginia Natural Gas10 10 
Chattanooga Gas7 2 
Nicor Gas3 3 
Total$43 $50 
Schedule of regulatory liabilities
Details of regulatory assets and (liabilities) reflected in the balance sheets at December 31, 2023 and 2022 are provided in the following tables:
Southern CompanyAlabama PowerGeorgia PowerMississippi PowerSouthern Company Gas
(in millions)
At December 31, 2023
AROs(a)(w)
$5,733 $1,936 $3,505 $247 $— 
Retiree benefit plans(b)(w)
3,011 815 976 140 146 
Remaining net book value of retired assets(c)
1,357 499 841 17 — 
Deferred income tax charges(d)
897 262 605 28 — 
Under recovered regulatory clause revenues(e)
413 381 — 12 20 
Fuel-hedging (realized and unrealized) losses(f)
270 100 121 49 — 
Deferred depreciation(g)
270 143 127 — — 
Environmental remediation(h)(w)
255 — 20 — 235 
Loss on reacquired debt(i)
238 35 197 5 1 
Vacation pay(j)(w)
217 83 107 11 16 
Software and cloud computing costs(k)
150 59 84 2 5 
Regulatory clauses(l)
140 112 — — 28 
Storm damage(m)
92 — 54 38 — 
Nuclear outage(n)
83 50 33 — — 
Long-term debt fair value adjustment(o)
60 — — — 60 
Qualifying repairs of natural gas distribution systems(p)
40 — — — 40 
Plant Daniel Units 3 and 4(q)
25 — — 25 — 
Kemper County energy facility assets, net(r)
7 — — 7 — 
Other regulatory assets(s)
182 39 33 18 93 
Deferred income tax credits(d)
(4,686)(1,506)(2,161)(241)(759)
Other cost of removal obligations(a)
(1,312)28 617 (186)(1,771)
Over recovered regulatory clause revenues(e)
(287)(3)(46)— (238)
Reliability reserves(t)
(179)(143)— (36)— 
Storm/property damage reserves(t)
(120)(76)— (44)— 
Customer refunds(u)
(19)(15)(4)— — 
Fuel-hedging (realized and unrealized) gains(f)
(6)(5)(1)— 
Other regulatory liabilities(v)
(308)(74)(18)(2)(101)
Total regulatory assets (liabilities), net$6,523 $2,720 $5,090 $90 $(2,225)
Southern CompanyAlabama PowerGeorgia PowerMississippi PowerSouthern Company Gas
(in millions)
At December 31, 2022
AROs(a)(w)
$6,096 $1,971 $3,829 $242 $— 
Retiree benefit plans(b)(w)
2,517 675 848 113 114 
Remaining net book value of retired assets(c)
1,543 562 962 19 — 
Under recovered regulatory clause revenues(e)
953 788 — 31 134 
Deferred income tax charges(d)
866 250 583 30 — 
Environmental remediation(h)(w)
294 — 25 — 269 
Loss on reacquired debt(i)
257 38 213 5 1 
Vacation pay(j)(w)
212 82 108 10 12 
Regulatory clauses(l)
142 142 — — — 
Software and cloud computing costs(k)
111 46 59 — 6 
Nuclear outage(n)
82 52 30 — — 
Long-term debt fair value adjustment(o)
69 — — — 69 
Fuel-hedging (realized and unrealized) losses(f)
60 15 45 — — 
Storm damage(m)
44 — — 44 — 
Plant Daniel Units 3 and 4(q)
27 — — 27 — 
Qualifying repairs of natural gas distribution systems(p)
26 — — — 26 
Kemper County energy facility assets, net(r)
20 — — 20 — 
Other regulatory assets(s)
171 36 27 16 92 
Deferred income tax credits(d)
(5,251)(1,925)(2,244)(269)(788)
Other cost of removal obligations(a)
(1,430)11 462 (196)(1,707)
Storm/property damage reserves(t)
(216)(97)(83)(36)— 
Reliability reserves(t)
(191)(166)— (25)— 
Customer refunds(u)
(183)(62)(121)— — 
Fuel-hedging (realized and unrealized) gains(f)
(83)(38)(21)(24)— 
Over recovered regulatory clause revenues(e)
(64)— (38)— (26)
Other regulatory liabilities(v)
(239)(40)(21)(3)(93)
Total regulatory assets (liabilities), net$5,833 $2,340 $4,663 $4 $(1,891)
Unless otherwise noted, the following recovery and amortization periods for these regulatory assets and (liabilities) have been approved by the respective state PSC or regulatory agency:
(a)AROs and other cost of removal obligations generally are recorded over the related property lives, which may range up to 64 years for Alabama Power, 56 years for Georgia Power, 55 years for Mississippi Power, and 85 years for Southern Company Gas. AROs and cost of removal obligations are settled and trued up following completion of the related activities. Alabama Power is recovering CCR ARO expenditures over a 38-year period ending in 2054 through Rate CNP Compliance. Effective January 1, 2023, Georgia Power is recovering CCR ARO expenditures over four-year periods through its ECCR tariff. Prior to 2023, expenditures were recovered over three-year periods. See "Georgia Power – Rate Plans" herein and Note 6 for additional information.
(b)Recovered and amortized over the average remaining service period, which may range up to 13 years for Alabama Power and Mississippi Power and up to 14 years for Georgia Power and Southern Company Gas. Southern Company's balances also include amounts at SCS and Southern Nuclear that are allocated to the applicable regulated utilities. See Note 11 for additional information.
(c)Alabama Power: Primarily represents the net book value of Plant Gorgas Unit 10 ($451 million at December 31, 2023) being amortized over 14 years (through 2037) and Plant Barry Unit 4 ($39 million at December 31, 2023) being amortized over 11 years (through 2034). See "Alabama Power – Environmental Accounting Order" herein for additional information.
Georgia Power: Net book values of Plant Wansley Units 1 and 2, Plant Hammond Units 1 through 4, and Plant Branch Unit 4 (totaling $488 million, $339 million, and $8 million, respectively, at December 31, 2023) are being amortized over remaining periods between one and 12 years (between 2024 and 2035). Balance also includes unusable materials and supplies inventories, for which the Georgia PSC will determine a recovery period in a future base rate case.
Mississippi Power: Represents net book value of certain environmental compliance assets at Plant Watson and Plant Greene County. The retail portion is being amortized over a 10-year period through 2030 and the wholesale portion is being amortized over a 14-year period through 2035. See "Mississippi Power – Environmental Compliance Overview Plan" herein for additional information.
(d)Deferred income tax charges are recovered and deferred income tax credits are primarily amortized over the related property lives, which may range up to 64 years for Alabama Power, 56 years for Georgia Power, 55 years for Mississippi Power, and 85 years for Southern Company Gas. See Note 10 for additional information. As a result of the Tax Reform Legislation, these accounts include certain deferred income tax assets and liabilities not subject to normalization, as described further below:
Alabama Power: Related amounts at December 31, 2023 include excess federal deferred income tax liabilities that are available for the benefit of customers in 2024 and/or 2025, as discussed under "Alabama Power – Excess Accumulated Deferred Income Tax Accounting Order" herein. Remaining amounts are being recovered and amortized ratably over the related property lives.
Georgia Power: Related amounts include $145 million of deferred income tax assets related to construction costs for Plant Vogtle Units 3 and 4 to be recovered over a 10-year period beginning the month after Unit 4 achieves commercial operation. See "Georgia Power – Nuclear Construction – Regulatory Matters" herein for additional information on recovery of costs related to Plant Vogtle Units 3 and 4.
Mississippi Power: Related amounts include retail deferred income tax liabilities ($11 million at December 31, 2023) that are expected to be fully amortized through 2024.
Southern Company Gas: Related amounts include deferred income tax liabilities ($1 million at December 31, 2023) being amortized through 2024. See "Southern Company Gas – Rate Proceedings" herein for additional information.
(e)Alabama Power: Balances are recorded monthly and expected to be recovered over periods of up to seven years, with the majority expected to be recovered within one year. See "Alabama Power – Rate CNP PPA," " – Rate CNP Compliance," and " – Rate ECR" herein for additional information.
Georgia Power: Balances are recorded monthly and expected to be recovered or returned within two years. See "Georgia Power – Rate Plans" herein for additional information.
Mississippi Power: At December 31, 2023, $12 million is expected to be recovered through various rate recovery mechanisms over a period to be determined in future rate filings. See "Mississippi Power – Ad Valorem Tax Adjustment" herein for additional information.
Southern Company Gas: Balances are recorded and recovered or amortized over periods generally not exceeding five years. In addition to natural gas cost recovery mechanisms, the natural gas distribution utilities have various other cost recovery mechanisms for the recovery of costs, including those related to infrastructure replacement programs.
(f)Fuel-hedging assets and liabilities are recorded over the life of the underlying hedged purchase contracts. Upon final settlement, actual costs incurred are recovered through the applicable traditional electric operating company's fuel cost recovery mechanism. Purchase contracts generally do not exceed three and a half years for Alabama Power, three years for Georgia Power, and four years for Mississippi Power.
(g)Alabama Power: Represents deferred depreciation expense for Plant Barry Unit 5 ($57 million at December 31, 2023) and Plant Barry common coal assets ($24 million at December 31, 2023) to be amortized until 2036 beginning when Plant Barry Unit 5 is retired and Plant Gaston Unit 5 coal assets ($62 million at December 31, 2023) to be amortized until 2039 beginning when the assets are retired.
Georgia Power: Represents deferred depreciation expense for Plant Scherer Units 1 through 3 ($70 million at December 31, 2023) to be amortized over six years beginning in 2029 and Plant Bowen Units 1 and 2 ($40 million at December 31, 2023) to be amortized over four years beginning in 2031, both as approved under Georgia Power's 2022 ARP, and Plant Vogtle Unit 3 and common facilities ($17 million at December 31, 2023) to be amortized over a 10-year period beginning the month after Plant Vogtle Unit 4 achieves commercial operation. See "Georgia Power – Nuclear Construction – Regulatory Matters" herein for additional information on recovery of costs related to Plant Vogtle Units 3 and 4.
(h)Effective January 1, 2023, Georgia Power is recovering $5 million annually for environmental remediation under the 2022 ARP. Southern Company Gas' costs are recovered through environmental cost recovery mechanisms when the remediation work is performed. See Note 3 under "Environmental Remediation" for additional information.
(i)Recovered over either the remaining life of the original issue or, if refinanced, over the remaining life of the new issue. At December 31, 2023, the remaining amortization periods do not exceed 24 years for Alabama Power, 29 years for Georgia Power, 18 years for Mississippi Power, and four years for Southern Company Gas.
(j)Recorded as earned by employees and recovered as paid, generally within one year. Includes both vacation and banked holiday pay, if applicable.
(k)Represents certain deferred operations and maintenance costs associated with software and cloud computing projects. For Alabama Power, costs are amortized ratably over the life of the related software, which ranges up to 10 years (through 2034). See "Alabama Power – Software Accounting Order" herein for additional information. For Georgia Power, costs incurred through 2022 are being amortized over five years (through 2027) and the recovery period for costs incurred after 2022 will be determined in its next base rate case. For Mississippi Power, the recovery period will be determined in Mississippi Power's annual PEP filing process. For Southern Company Gas, costs are being amortized ratably over the life of the related software, which ranges up to 10 years (through 2034).
(l)Alabama Power: Effective January 1, 2023, balance is being amortized through Rate RSE over a five-year period ending in 2027.
Southern Company Gas: Represents amounts related to Nicor Gas' volume balancing adjustment rider expected to be recovered over a period of less than two years.
(m)See "Georgia Power – Storm Damage Recovery" herein and Note 1 under "Storm Damage and Reliability Reserves" for additional information. Mississippi Power's balance represents deferred storm costs associated with Hurricanes Ida and Zeta being recovered through PEP over a seven-year period through 2029.
(n)Nuclear outage costs are deferred to a regulatory asset when incurred and amortized over a subsequent period of 18 months for Alabama Power and up to 24 months for Georgia Power. See Note 5 for additional information.
(o)Recovered over the remaining lives of the original debt issuances at acquisition, which range up to 15 years at December 31, 2023.
(p)Represents deferred costs of certain repairs at Atlanta Gas Light being amortized over 20 years.
(q)Represents the difference between Mississippi Power's revenue requirement for Plant Daniel Units 3 and 4 under purchase accounting and operating lease accounting. At December 31, 2023, consists of the $17 million retail portion being amortized through 2039 over the remaining life of the related property and the $8 million wholesale portion being amortized through 2035.
(r)At December 31, 2023, includes $9 million of regulatory assets (wholesale) expected to be fully amortized by 2035 and $2 million of regulatory liabilities (retail) expected to be fully amortized by 2024.
(s)Comprised of numerous immaterial components with remaining amortization periods at December 31, 2023 generally not exceeding 20 years for Alabama Power, 10 years for Georgia Power, 14 years for Mississippi Power, and 15 years for Southern Company Gas.
(t)Utilized as related expenses are incurred. See "Alabama Power – Rate NDR" and " – Reliability Reserve Accounting Order," "Georgia Power – Storm Damage Recovery," and "Mississippi Power – System Restoration Rider" and " – Reliability Reserve Accounting Order" herein and Note 1 under "Storm Damage and Reliability Reserves" for additional information.
(u)Primarily includes approximately $15 million and $62 million at December 31, 2023 and 2022, respectively, for Alabama Power and $119 million at December 31, 2022 for Georgia Power as a result of each company exceeding its allowed retail return range. Georgia Power's balances also include immaterial amounts related to refunds for transmission service customers. See "Alabama Power – Rate RSE" and "Georgia Power – Rate Plans" herein for additional information.
(v)Comprised of numerous immaterial components with remaining amortization periods at December 31, 2023 generally not exceeding 11 years for Alabama Power, nine years for Georgia Power, four years for Mississippi Power, and 20 years for Southern Company Gas.
(w)Generally not earning a return as they are excluded from rate base or are offset in rate base by a corresponding asset or liability.
Public utilities general disclosures Details of tariff adjustments are provided in the following table:
Tariff20232024
(in millions)
Traditional base$194 $275 
ECCR(21)(99)
DSM37 10 
MFF6 5 
Total$216 $191 
The Georgia PSC approved the following tariff adjustments under the 2019 ARP effective January 1 2022:
Tariff2022
(in millions)
Traditional base$192 
ECCR(12)
DSM(25)
MFF2 
Total$157 
The following table provides regulatory information for Southern Company Gas' natural gas distribution utilities:
Nicor GasAtlanta Gas LightVirginia Natural GasChattanooga Gas
Authorized ROE at December 31, 2023
9.51%10.25%9.70%9.80%
Weather normalization mechanisms(a)
üü
Decoupled, including straight-fixed-variable rates(b)
üüü
Regulatory infrastructure program rate(c)
üüüü
Bad debt rider(d)
üüü
Energy efficiency plan(e)
üü
Annual base rate adjustment mechanism(f)
üü
Year of last base rate case decision2023201920232018
(a)Designed to help stabilize operating results by allowing recovery of costs in the event of unseasonal weather, but are not direct offsets to the potential impacts on earnings of weather and customer consumption.
(b)Allows for recovery of fixed customer service costs separately from assumed natural gas volumes used by customers and provides a benchmark level of revenue for recovery.
(c)See "Infrastructure Replacement Programs and Capital Projects" herein for additional information. Chattanooga Gas' pipeline replacement program costs are recovered through its annual base rate review mechanism.
(d)The recovery (refund) of bad debt expense over (under) an established benchmark expense. The gas portion of bad debt expense is recovered through purchased gas adjustment mechanisms. Nicor Gas also has a rider to recover the non-gas portion of bad debt expense.
(e)Recovery of costs associated with plans to achieve specified energy savings goals.
(f)Regulatory mechanism allowing annual adjustments to base rates up or down based on authorized ROE and/or ROE range.
The following table and discussions provide updates on the infrastructure replacement programs and capital projects at the natural gas distribution utilities at December 31, 2023. These programs are risk-based and designed to update and replace cast iron, bare steel, and mid-vintage plastic materials or expand Southern Company Gas' distribution systems to improve reliability and meet operational flexibility and growth.
UtilityProgramRecovery
Capital Expenditures in 2023
Capital Expenditures Since Project Inception
Pipe
Installed Since
Project Inception		Scope of
Program		Program DurationLast
Year of Program
(in millions)(miles)(miles)(years)
Nicor Gas
Investing in Illinois Qualifying Infrastructure Plant(*)
Rider$365 $3,228 1,367 1,367 92023
Virginia Natural Gas
SAVE
Rider75 486 567 695 132024
Atlanta Gas LightSystem Reinforcement RiderRider104 180 20 N/A32024
Chattanooga GasPipeline Replacement ProgramRate Base9 16 15 73 72027
Total$553 $3,910 1,969 2,135 
(*)Included replacement of pipes, compressors, and transmission mains along with other improvements such as new meters. This program ended November 30, 2023 with all expenditures placed in service. Recovery of program costs is described under "Nicor Gas" herein.
The following table provides a summary of QIP capital investments during the nine-year program:
Year Status of QIP Annual Review Proceeding
Capital Investments
DisallowedMonth of Disallowance
(in millions)
2015 – 2018Complete$1,246 $— 
2019
Complete(a)
415 32 June 2023
2020
Filed March 2021
402 
(b)
2021
Filed March 2022
392 
(b)
2022
Filed March 2023
408 
(b)
6 
(a)(c)
November 2023
2023
To be filed by March 20, 2024
365 
(b)
25 
(a)(c)
November 2023
$3,228 $63 
(a)Appealed to the Illinois Appellate Court.
(b)Capital investments are subject to the required QIP annual review proceeding; years 2020 through 2022 are pending with the Illinois Commission.
(c)Disallowed in Nicor Gas' 2023 general base rate case proceeding. See "Rate Proceedings – Nicor Gas" herein for additional information regarding the Illinois Commission's disallowance of certain capital investments.
Schedule of revised cost and schedule
Georgia Power's approximate proportionate share of the remaining estimated capital cost to complete Plant Vogtle Units 3 and 4, including contingency, through the second quarter 2024 is as follows:
(in millions)
Base project capital cost forecast(a)(b)
$10,717 
Construction contingency estimate36 
Total project capital cost forecast(a)(b)
10,753 
Net investment at December 31, 2023(b)
(10,564)
Remaining estimate to complete$189 
(a)Includes approximately $610 million of costs that are not shared with the other Vogtle Owners, including $33 million of construction monitoring costs, and approximately $567 million of incremental costs under the cost-sharing provisions of the joint ownership agreements described below. Excludes financing costs expected to be capitalized through AFUDC of approximately $440 million, of which $417 million had been accrued through December 31, 2023.
(b)Net of $1.7 billion received from Toshiba under the Guarantee Settlement Agreement and approximately $188 million in related customer refunds.