Debt

12 Months Ended

Dec. 31, 2020

Debt Instrument [Line Items]

Debt

DEBT(a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2020, the short-term borrowing capacity under a single credit facility agreement, which expires in August 2023, totaled $1 billion ($450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $500 million, $400 million and $500 million, respectively, within the $1 billion total commitment. Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions):

	Alliant Energy		IPL		WPL
December 31	2020	2019	2020	2019	2020	2019
Amount outstanding	$389	$337	$—	$—	$257	$168
Weighted average interest rates	0.2%	1.9%	N/A	N/A	0.1%	1.8%
Available credit facility capacity	$611	$663	$250	$250	$43	$132

	Alliant Energy		IPL		WPL
For the year ended	2020	2019	2020	2019	2020	2019
Maximum amount outstanding (based on daily outstanding balances)	$495	$601	$8	$50	$266	$195
Average amount outstanding (based on daily outstanding balances)	$292	$453	$—	$—	$117	$93
Weighted average interest rates	0.7%	2.5%	0.5%	2.8%	0.7%	2.4%

(b) Long-Term Debt - Long-term debt, net as of December 31 was as follows (dollars in millions):

	2020			2019
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Senior Debentures (a):
3.25%, due 2024	$500	$500	$—	$500	$500	$—
3.4%, due 2025	250	250	—	250	250	—
5.5%, due 2025	50	50	—	50	50	—
4.1%, due 2028	500	500	—	500	500	—
3.6%, due 2029	300	300	—	300	300	—
2.3%, due 2030 (b)	400	400	—	—	—	—
6.45%, due 2033	100	100	—	100	100	—
6.3%, due 2034	125	125	—	125	125	—
6.25%, due 2039	300	300	—	300	300	—
4.7%, due 2043	250	250	—	250	250	—
3.7%, due 2046	300	300	—	300	300	—
3.5%, due 2049	300	300	—	300	300	—
3.65% (Retired in 2020)	—	—	—	200	200	—
	3,375	3,375	—	3,175	3,175	—
Debentures (a):
2.25%, due 2022	250	—	250	250	—	250
3.05%, due 2027	300	—	300	300	—	300
3%, due 2029	350	—	350	350	—	350
6.25%, due 2034	100	—	100	100	—	100
6.375%, due 2037	300	—	300	300	—	300
7.6%, due 2038	250	—	250	250	—	250
4.1%, due 2044	250	—	250	250	—	250
3.65%, due 2050 (c)	350	—	350	—	—	—
4.6% (Retired in 2020)	—	—	—	150	—	150
	2,150	—	2,150	1,950	—	1,950
Other:
AEF term loan credit agreement through March 2022, 1% at December 31, 2020 (with Alliant Energy as guarantor) (d)	300	—	—	—	—	—
Corporate Services 3.45% senior notes, due 2022 (a)	75	—	—	75	—	—
AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a)	400	—	—	400	—	—
AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a)(e)	200	—	—	—	—	—
AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a)	300	—	—	300	—	—
Sheboygan Power, LLC 5.06% senior secured notes, due 2021 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a)	31	—	—	38	—	—
AEF term loan credit agreement, 2% at December 31, 2019 (with Alliant Energy as guarantor) (Retired in 2020)	—	—	—	300	—	—
Other, 1% at December 31, 2020, due 2021 to 2025	2	—	—	2	—	—
	1,308	—	—	1,115	—	—
Subtotal	6,833	3,375	2,150	6,240	3,175	1,950
Current maturities	(8)	—	—	(657)	(200)	(150)
Unamortized debt issuance costs	(41)	(22)	(14)	(37)	(21)	(11)
Unamortized debt (discount) and premium, net	(15)	(8)	(6)	(13)	(7)	(6)
Long-term debt, net (f)	$6,769	$3,345	$2,130	$5,533	$2,947	$1,783

(a)Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption.

(b)In June 2020, IPL issued $400 million of 2.3% senior debentures due 2030. The net proceeds from the issuance were used by IPL to retire its $200 million 3.65% senior debentures that would have matured in September 2020 and for general corporate purposes.

(c)In April 2020, WPL issued $350 million of 3.65% debentures due 2050. The net proceeds from the issuance were used by WPL to reduce borrowings under the single credit facility and for general corporate purposes.

(d)In March 2020, AEF entered into a $300 million variable-rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable-rate term loan credit agreement that would have expired in April 2020.

(e)In November 2020, AEF issued $200 million of 1.4% senior notes due 2026. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes.

(f)There were no significant sinking fund requirements related to the outstanding long-term debt.

Five-Year Schedule of Long-term Debt Maturities - At December 31, 2020, long-term debt maturities for 2021 through 2025 were as follows (in millions):

	2021	2022	2023	2024	2025
IPL	$—	$—	$—	$500	$300
WPL	—	250	—	—	—
Corporate Services	—	75	—	—	—
AEF	8	308	408	9	—
Alliant Energy	$8	$633	$408	$509	$300

Fair Value of Long-term Debt - Refer to Note 16 for information on the fair value of long-term debt outstanding.

IPL [Member]

Debt Instrument [Line Items]

Debt

DEBT(a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2020, the short-term borrowing capacity under a single credit facility agreement, which expires in August 2023, totaled $1 billion ($450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $500 million, $400 million and $500 million, respectively, within the $1 billion total commitment. Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions):

	Alliant Energy		IPL		WPL
December 31	2020	2019	2020	2019	2020	2019
Amount outstanding	$389	$337	$—	$—	$257	$168
Weighted average interest rates	0.2%	1.9%	N/A	N/A	0.1%	1.8%
Available credit facility capacity	$611	$663	$250	$250	$43	$132

	Alliant Energy		IPL		WPL
For the year ended	2020	2019	2020	2019	2020	2019
Maximum amount outstanding (based on daily outstanding balances)	$495	$601	$8	$50	$266	$195
Average amount outstanding (based on daily outstanding balances)	$292	$453	$—	$—	$117	$93
Weighted average interest rates	0.7%	2.5%	0.5%	2.8%	0.7%	2.4%

(b) Long-Term Debt - Long-term debt, net as of December 31 was as follows (dollars in millions):

	2020			2019
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Senior Debentures (a):
3.25%, due 2024	$500	$500	$—	$500	$500	$—
3.4%, due 2025	250	250	—	250	250	—
5.5%, due 2025	50	50	—	50	50	—
4.1%, due 2028	500	500	—	500	500	—
3.6%, due 2029	300	300	—	300	300	—
2.3%, due 2030 (b)	400	400	—	—	—	—
6.45%, due 2033	100	100	—	100	100	—
6.3%, due 2034	125	125	—	125	125	—
6.25%, due 2039	300	300	—	300	300	—
4.7%, due 2043	250	250	—	250	250	—
3.7%, due 2046	300	300	—	300	300	—
3.5%, due 2049	300	300	—	300	300	—
3.65% (Retired in 2020)	—	—	—	200	200	—
	3,375	3,375	—	3,175	3,175	—
Debentures (a):
2.25%, due 2022	250	—	250	250	—	250
3.05%, due 2027	300	—	300	300	—	300
3%, due 2029	350	—	350	350	—	350
6.25%, due 2034	100	—	100	100	—	100
6.375%, due 2037	300	—	300	300	—	300
7.6%, due 2038	250	—	250	250	—	250
4.1%, due 2044	250	—	250	250	—	250
3.65%, due 2050 (c)	350	—	350	—	—	—
4.6% (Retired in 2020)	—	—	—	150	—	150
	2,150	—	2,150	1,950	—	1,950
Other:
AEF term loan credit agreement through March 2022, 1% at December 31, 2020 (with Alliant Energy as guarantor) (d)	300	—	—	—	—	—
Corporate Services 3.45% senior notes, due 2022 (a)	75	—	—	75	—	—
AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a)	400	—	—	400	—	—
AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a)(e)	200	—	—	—	—	—
AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a)	300	—	—	300	—	—
Sheboygan Power, LLC 5.06% senior secured notes, due 2021 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a)	31	—	—	38	—	—
AEF term loan credit agreement, 2% at December 31, 2019 (with Alliant Energy as guarantor) (Retired in 2020)	—	—	—	300	—	—
Other, 1% at December 31, 2020, due 2021 to 2025	2	—	—	2	—	—
	1,308	—	—	1,115	—	—
Subtotal	6,833	3,375	2,150	6,240	3,175	1,950
Current maturities	(8)	—	—	(657)	(200)	(150)
Unamortized debt issuance costs	(41)	(22)	(14)	(37)	(21)	(11)
Unamortized debt (discount) and premium, net	(15)	(8)	(6)	(13)	(7)	(6)
Long-term debt, net (f)	$6,769	$3,345	$2,130	$5,533	$2,947	$1,783

(a)Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption.

(b)In June 2020, IPL issued $400 million of 2.3% senior debentures due 2030. The net proceeds from the issuance were used by IPL to retire its $200 million 3.65% senior debentures that would have matured in September 2020 and for general corporate purposes.

(c)In April 2020, WPL issued $350 million of 3.65% debentures due 2050. The net proceeds from the issuance were used by WPL to reduce borrowings under the single credit facility and for general corporate purposes.

(d)In March 2020, AEF entered into a $300 million variable-rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable-rate term loan credit agreement that would have expired in April 2020.

(e)In November 2020, AEF issued $200 million of 1.4% senior notes due 2026. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes.

(f)There were no significant sinking fund requirements related to the outstanding long-term debt.

Five-Year Schedule of Long-term Debt Maturities - At December 31, 2020, long-term debt maturities for 2021 through 2025 were as follows (in millions):

	2021	2022	2023	2024	2025
IPL	$—	$—	$—	$500	$300
WPL	—	250	—	—	—
Corporate Services	—	75	—	—	—
AEF	8	308	408	9	—
Alliant Energy	$8	$633	$408	$509	$300

Fair Value of Long-term Debt - Refer to Note 16 for information on the fair value of long-term debt outstanding.

WPL [Member]

Debt Instrument [Line Items]

Debt

DEBT(a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2020, the short-term borrowing capacity under a single credit facility agreement, which expires in August 2023, totaled $1 billion ($450 million for Alliant Energy at the parent company level, $250 million for IPL and $300 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $500 million, $400 million and $500 million, respectively, within the $1 billion total commitment. Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper, and Alliant Energy’s and WPL’s borrowings under the single credit facility, classified as short-term debt was as follows (dollars in millions):

	Alliant Energy		IPL		WPL
December 31	2020	2019	2020	2019	2020	2019
Amount outstanding	$389	$337	$—	$—	$257	$168
Weighted average interest rates	0.2%	1.9%	N/A	N/A	0.1%	1.8%
Available credit facility capacity	$611	$663	$250	$250	$43	$132

	Alliant Energy		IPL		WPL
For the year ended	2020	2019	2020	2019	2020	2019
Maximum amount outstanding (based on daily outstanding balances)	$495	$601	$8	$50	$266	$195
Average amount outstanding (based on daily outstanding balances)	$292	$453	$—	$—	$117	$93
Weighted average interest rates	0.7%	2.5%	0.5%	2.8%	0.7%	2.4%

(b) Long-Term Debt - Long-term debt, net as of December 31 was as follows (dollars in millions):

	2020			2019
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Senior Debentures (a):
3.25%, due 2024	$500	$500	$—	$500	$500	$—
3.4%, due 2025	250	250	—	250	250	—
5.5%, due 2025	50	50	—	50	50	—
4.1%, due 2028	500	500	—	500	500	—
3.6%, due 2029	300	300	—	300	300	—
2.3%, due 2030 (b)	400	400	—	—	—	—
6.45%, due 2033	100	100	—	100	100	—
6.3%, due 2034	125	125	—	125	125	—
6.25%, due 2039	300	300	—	300	300	—
4.7%, due 2043	250	250	—	250	250	—
3.7%, due 2046	300	300	—	300	300	—
3.5%, due 2049	300	300	—	300	300	—
3.65% (Retired in 2020)	—	—	—	200	200	—
	3,375	3,375	—	3,175	3,175	—
Debentures (a):
2.25%, due 2022	250	—	250	250	—	250
3.05%, due 2027	300	—	300	300	—	300
3%, due 2029	350	—	350	350	—	350
6.25%, due 2034	100	—	100	100	—	100
6.375%, due 2037	300	—	300	300	—	300
7.6%, due 2038	250	—	250	250	—	250
4.1%, due 2044	250	—	250	250	—	250
3.65%, due 2050 (c)	350	—	350	—	—	—
4.6% (Retired in 2020)	—	—	—	150	—	150
	2,150	—	2,150	1,950	—	1,950
Other:
AEF term loan credit agreement through March 2022, 1% at December 31, 2020 (with Alliant Energy as guarantor) (d)	300	—	—	—	—	—
Corporate Services 3.45% senior notes, due 2022 (a)	75	—	—	75	—	—
AEF 3.75% senior notes, due 2023 (with Alliant Energy as guarantor) (a)	400	—	—	400	—	—
AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a)(e)	200	—	—	—	—	—
AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a)	300	—	—	300	—	—
Sheboygan Power, LLC 5.06% senior secured notes, due 2021 to 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a)	31	—	—	38	—	—
AEF term loan credit agreement, 2% at December 31, 2019 (with Alliant Energy as guarantor) (Retired in 2020)	—	—	—	300	—	—
Other, 1% at December 31, 2020, due 2021 to 2025	2	—	—	2	—	—
	1,308	—	—	1,115	—	—
Subtotal	6,833	3,375	2,150	6,240	3,175	1,950
Current maturities	(8)	—	—	(657)	(200)	(150)
Unamortized debt issuance costs	(41)	(22)	(14)	(37)	(21)	(11)
Unamortized debt (discount) and premium, net	(15)	(8)	(6)	(13)	(7)	(6)
Long-term debt, net (f)	$6,769	$3,345	$2,130	$5,533	$2,947	$1,783

(a)Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption.

(b)In June 2020, IPL issued $400 million of 2.3% senior debentures due 2030. The net proceeds from the issuance were used by IPL to retire its $200 million 3.65% senior debentures that would have matured in September 2020 and for general corporate purposes.

(c)In April 2020, WPL issued $350 million of 3.65% debentures due 2050. The net proceeds from the issuance were used by WPL to reduce borrowings under the single credit facility and for general corporate purposes.

(d)In March 2020, AEF entered into a $300 million variable-rate term loan credit agreement and used the borrowings under this agreement to retire its $300 million variable-rate term loan credit agreement that would have expired in April 2020.

(e)In November 2020, AEF issued $200 million of 1.4% senior notes due 2026. The net proceeds from the issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes.

(f)There were no significant sinking fund requirements related to the outstanding long-term debt.

Five-Year Schedule of Long-term Debt Maturities - At December 31, 2020, long-term debt maturities for 2021 through 2025 were as follows (in millions):

	2021	2022	2023	2024	2025
IPL	$—	$—	$—	$500	$300
WPL	—	250	—	—	—
Corporate Services	—	75	—	—	—
AEF	8	308	408	9	—
Alliant Energy	$8	$633	$408	$509	$300

Fair Value of Long-term Debt - Refer to Note 16 for information on the fair value of long-term debt outstanding.