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Property, Plant and Equipment | 12 Months Ended
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Dec. 31, 2015
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | PROPERTY, PLANT AND EQUIPMENT At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
In service: |  |  |  |  |  |  |  |  |  |  |
Generation |  | $5,643.7 |  |  |  | $5,463.0 |  |  |  | $3,011.6 |  |  |  | $2,872.4 |  |  |  | $2,632.1 |  |  |  | $2,590.6 |
Distribution | 4,489.9 |  |  | 4,435.4 |  |  | 2,447.9 |  |  | 2,471.7 |  |  | 2,042.0 |  |  | 1,963.7 |
Other | 311.3 |  |  | 309.1 |  |  | 212.2 |  |  | 215.5 |  |  | 99.1 |  |  | 93.6 |
Anticipated to be retired early (a) | — |  |  | 157.6 |  |  | — |  |  | — |  |  | — |  |  | 157.6 |
Total electric plant | 10,444.9 |  |  | 10,365.1 |  |  | 5,671.7 |  |  | 5,559.6 |  |  | 4,773.2 |  |  | 4,805.5 |
Gas plant in service | 1,018.3 |  |  | 946.2 |  |  | 513.6 |  |  | 474.0 |  |  | 504.7 |  |  | 472.2 |
Other plant in service | 530.6 |  |  | 539.3 |  |  | 296.0 |  |  | 298.8 |  |  | 234.6 |  |  | 240.5 |
Accumulated depreciation (a) | (3,939.6 | ) |  | (3,923.1 | ) |  | (2,152.8 | ) |  | (2,124.5 | ) |  | (1,786.8 | ) |  | (1,798.6 | )
Net plant | 8,054.2 |  |  | 7,927.5 |  |  | 4,328.5 |  |  | 4,207.9 |  |  | 3,725.7 |  |  | 3,719.6 |
Leased Sheboygan Falls Energy Facility, net (b) | — |  |  | — |  |  | — |  |  | — |  |  | 58.6 |  |  | 64.7 |
Construction work in progress | 897.5 |  |  | 479.1 |  |  | 578.2 |  |  | 325.0 |  |  | 319.3 |  |  | 154.1 |
Other, net | 18.5 |  |  | 22.3 |  |  | 18.4 |  |  | 21.8 |  |  | 0.1 |  |  | 0.5 |
Total utility | 8,970.2 |  |  | 8,428.9 |  |  | 4,925.1 |  |  | 4,554.7 |  |  | 4,103.7 |  |  | 3,938.9 |
Non-regulated and other: |  |  |  |  |  |  |  |  |  |  |
Non-regulated Generation, net (c) | 229.3 |  |  | 240.1 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (d) | 319.6 |  |  | 269.4 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-regulated and other | 548.9 |  |  | 509.5 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $9,519.1 |  |  |  | $8,938.4 |  |  |  | $4,925.1 |  |  |  | $4,554.7 |  |  |  | $4,103.7 |  |  |  | $3,938.9 |
(a) | In December 2015, WPL retired Nelson Dewey Units 1 and 2 and Edgewater Unit 3 and transferred the remaining net book value from property, plant and equipment to regulatory assets pursuant to orders from the PSCW and FERC. Refer to Note 2 for discussion of the recovery of the remaining net book value of these EGUs.
(b) | Less accumulated amortization of $65.2 million and $59.1 million for WPL as of December 31, 2015 and 2014, respectively.
(c) | Less accumulated depreciation of $59.0 million and $49.5 million for Alliant Energy as of December 31, 2015 and 2014, respectively.
(d) | Less accumulated depreciation of $252.9 million and $229.1 million for Alliant Energy as of December 31, 2015 and 2014, respectively.
Utility - Environmental Controls Project - WPL’s Edgewater Unit 5 - WPL is currently constructing a scrubber and baghouse at Edgewater Unit 5. The scrubber and baghouse reduce SO2 and mercury emissions at the EGU and are expected to help meet requirements under the MATS Rule and CSAPR. Construction began in 2014 and is expected to be completed in 2016. As of December 31, 2015 and 2014, Alliant Energy and WPL recorded capitalized expenditures for CWIP of $190 million and $90 million, and AFUDC of $8 million and $3 million, respectively, for the scrubber and baghouse in “Construction work in progress” in the above table for Alliant Energy and WPL. Natural Gas-Fired Generation Project - IPL’s Marshalltown Generating Station - IPL is currently constructing Marshalltown, an approximate 650 MW natural gas-fired combined-cycle EGU. Construction began in 2014 and is expected to be completed in 2017. As of December 31, 2015 and 2014, Alliant Energy and IPL recorded capitalized expenditures for CWIP of $453 million and $188 million, and AFUDC of $24 million and $4 million, respectively, for Marshalltown in “Construction work in progress” in the above table for Alliant Energy and IPL. Sales of IPL’s Minnesota Electric and Natural Gas Distribution Assets - In April 2015, IPL completed the sale of its Minnesota natural gas distribution assets (primarily related to property, plant and equipment) to Minnesota Energy Resources Corporation, a subsidiary of Integrys Energy Group, Inc. IPL received proceeds of $11 million and a promissory note of $2 million. In July 2015, IPL completed the sale of its Minnesota electric distribution assets (primarily related to property, plant and equipment) to Southern Minnesota Energy Cooperative, a combined group of various neighboring electric cooperatives, and received proceeds of $129 million. The proceeds from the natural gas distribution assets were used for general corporate purposes and the proceeds from the electric distribution assets were used to reduce cash amounts received from IPL’s sales of accounts receivable program. The premium received over the book value of the property, plant and equipment sold was more than offset by a reduction in tax-related regulatory assets associated with the distribution assets. As a result, Alliant Energy and IPL recorded pre-tax charges of $11 million and $3 million for the Minnesota electric and natural gas distribution asset transactions, respectively, in “Other operation and maintenance” in their income statements in 2015. The electric distribution asset sales agreement includes a wholesale power supply agreement between IPL and Southern Minnesota Energy Cooperative, which was approved by FERC in July 2015 and became effective upon the sale of IPL’s Minnesota electric distribution assets. The wholesale power supply agreement contains a five-year termination notice, which may not be given until the fifth anniversary of the effective date of the agreement, resulting in a minimum term of 10 years. The agreement remains in effect indefinitely, unless notice to terminate is provided by either party. This wholesale power supply agreement includes standardized pricing mechanisms that are detailed in IPL’s current tariffs accepted by FERC through wholesale rate case proceedings. IPL’s current return on common equity authorized by FERC related to its wholesale electric rates is 10.97%. As a result of IPL’s requirement to supply electricity to Southern Minnesota Energy Cooperative under the wholesale power supply agreement, the sale of the electric distribution assets did not have a significant impact on IPL’s generation plans or operating results. Refer to Note 19 for further discussion of IPL’s sales of its Minnesota electric and natural gas distribution assets. AFUDC - AFUDC represents costs to finance construction additions including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Equity |  | $24.4 |  |  |  | $23.1 |  |  |  | $20.3 |  |  |  | $18.6 |  |  |  | $17.1 |  |  |  | $13.8 |  |  |  | $5.8 |  |  |  | $6.0 |  |  |  | $6.5 |
Debt | 12.5 |  |  | 11.7 |  |  | 10.5 |  |  | 9.6 |  |  | 8.8 |  |  | 7.2 |  |  | 2.9 |  |  | 2.9 |  |  | 3.3 |
|  | $36.9 |  |  |  | $34.8 |  |  |  | $30.8 |  |  |  | $28.2 |  |  |  | $25.9 |  |  |  | $21.0 |  |  |  | $8.7 |  |  |  | $8.9 |  |  |  | $9.8 |
AFUDC related to various construction projects was recognized in the income statements as follows (in millions):
| 2015 |  | 2014 |  | 2013
IPL: |  |  |  |  |
Marshalltown |  | $20.7 |  |  |  | $3.7 |  |  |  | $— |
Environmental controls - Ottumwa Unit 1 | — |  |  | 10.6 |  |  | 8.0 |
Environmental controls - George Neal Units 3 and 4 | — |  |  | 1.4 |  |  | 5.1 |
Other | 7.5 |  |  | 10.2 |  |  | 7.9 |
| 28.2 |  |  | 25.9 |  |  | 21.0 |
WPL: |  |  |  |  |
Environmental controls - Edgewater Unit 5 | 5.1 |  |  | 2.7 |  |  | — |
Environmental controls - Columbia Units 1 and 2 | — |  |  | 4.0 |  |  | 7.2 |
Other | 3.6 |  |  | 2.2 |  |  | 2.6 |
| 8.7 |  |  | 8.9 |  |  | 9.8 |
Alliant Energy |  | $36.9 |  |  |  | $34.8 |  |  |  | $30.8 |
In 2014, scrubbers and baghouses were placed in service at IPL’s Ottumwa Unit 1 and George Neal Unit 3, and WPL’s Columbia Units 1 and 2. In 2013, a scrubber and baghouse was placed in service at IPL’s George Neal Unit 4. Non-regulated and Other - The non-regulated and other property, plant and equipment recorded on Alliant Energy’s balance sheets includes the following: Non-regulated Generation - Franklin County Wind Farm - The Franklin County wind farm was placed into service in 2012 and is depreciated using the straight-line method over a 30-year period. As of December 31, 2015, Alliant Energy recorded $130 million on its balance sheet related to the wind farm. Refer to Note 1(i) for discussion of an impairment test performed as of December 31, 2015 related to the wind farm. Refer to Note 5(d) for discussion of a cash grant received in 2013 related to the wind farm. Sheboygan Falls - Sheboygan Falls was placed into service in 2005 and is depreciated using the straight-line method over a 35-year period. As of December 31, 2015, Alliant Energy recorded $99 million on its balance sheet related to Sheboygan Falls. Corporate Services and Other - Property, plant and equipment related to Corporate Services includes computer software and the corporate headquarters building located in Madison, Wisconsin. In addition, Corporate Services implemented a new customer billing and information system for IPL and WPL, which was placed in service in the fourth quarter of 2015 and is amortized using the straight-line method over a 12-year period. As of December 31, 2015, Alliant Energy recorded capitalized expenditures of $102 million and capitalized interest of $3 million for the customer billing and information system in “Corporate Services and other, net” in the above table for Alliant Energy. Property, plant and equipment related to Transportation includes a short-line railway in Iowa, a barge terminal on the Mississippi River and a coal terminal in Williams, Iowa. The Corporate Services and Other property, plant and equipment is depreciated using the straight-line method over periods ranging from 5 to 30 years.
IPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | PROPERTY, PLANT AND EQUIPMENT At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
In service: |  |  |  |  |  |  |  |  |  |  |
Generation |  | $5,643.7 |  |  |  | $5,463.0 |  |  |  | $3,011.6 |  |  |  | $2,872.4 |  |  |  | $2,632.1 |  |  |  | $2,590.6 |
Distribution | 4,489.9 |  |  | 4,435.4 |  |  | 2,447.9 |  |  | 2,471.7 |  |  | 2,042.0 |  |  | 1,963.7 |
Other | 311.3 |  |  | 309.1 |  |  | 212.2 |  |  | 215.5 |  |  | 99.1 |  |  | 93.6 |
Anticipated to be retired early (a) | — |  |  | 157.6 |  |  | — |  |  | — |  |  | — |  |  | 157.6 |
Total electric plant | 10,444.9 |  |  | 10,365.1 |  |  | 5,671.7 |  |  | 5,559.6 |  |  | 4,773.2 |  |  | 4,805.5 |
Gas plant in service | 1,018.3 |  |  | 946.2 |  |  | 513.6 |  |  | 474.0 |  |  | 504.7 |  |  | 472.2 |
Other plant in service | 530.6 |  |  | 539.3 |  |  | 296.0 |  |  | 298.8 |  |  | 234.6 |  |  | 240.5 |
Accumulated depreciation (a) | (3,939.6 | ) |  | (3,923.1 | ) |  | (2,152.8 | ) |  | (2,124.5 | ) |  | (1,786.8 | ) |  | (1,798.6 | )
Net plant | 8,054.2 |  |  | 7,927.5 |  |  | 4,328.5 |  |  | 4,207.9 |  |  | 3,725.7 |  |  | 3,719.6 |
Leased Sheboygan Falls Energy Facility, net (b) | — |  |  | — |  |  | — |  |  | — |  |  | 58.6 |  |  | 64.7 |
Construction work in progress | 897.5 |  |  | 479.1 |  |  | 578.2 |  |  | 325.0 |  |  | 319.3 |  |  | 154.1 |
Other, net | 18.5 |  |  | 22.3 |  |  | 18.4 |  |  | 21.8 |  |  | 0.1 |  |  | 0.5 |
Total utility | 8,970.2 |  |  | 8,428.9 |  |  | 4,925.1 |  |  | 4,554.7 |  |  | 4,103.7 |  |  | 3,938.9 |
Non-regulated and other: |  |  |  |  |  |  |  |  |  |  |
Non-regulated Generation, net (c) | 229.3 |  |  | 240.1 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (d) | 319.6 |  |  | 269.4 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-regulated and other | 548.9 |  |  | 509.5 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $9,519.1 |  |  |  | $8,938.4 |  |  |  | $4,925.1 |  |  |  | $4,554.7 |  |  |  | $4,103.7 |  |  |  | $3,938.9 |
(a) | In December 2015, WPL retired Nelson Dewey Units 1 and 2 and Edgewater Unit 3 and transferred the remaining net book value from property, plant and equipment to regulatory assets pursuant to orders from the PSCW and FERC. Refer to Note 2 for discussion of the recovery of the remaining net book value of these EGUs.
(b) | Less accumulated amortization of $65.2 million and $59.1 million for WPL as of December 31, 2015 and 2014, respectively.
(c) | Less accumulated depreciation of $59.0 million and $49.5 million for Alliant Energy as of December 31, 2015 and 2014, respectively.
(d) | Less accumulated depreciation of $252.9 million and $229.1 million for Alliant Energy as of December 31, 2015 and 2014, respectively.
Utility - Environmental Controls Project - WPL’s Edgewater Unit 5 - WPL is currently constructing a scrubber and baghouse at Edgewater Unit 5. The scrubber and baghouse reduce SO2 and mercury emissions at the EGU and are expected to help meet requirements under the MATS Rule and CSAPR. Construction began in 2014 and is expected to be completed in 2016. As of December 31, 2015 and 2014, Alliant Energy and WPL recorded capitalized expenditures for CWIP of $190 million and $90 million, and AFUDC of $8 million and $3 million, respectively, for the scrubber and baghouse in “Construction work in progress” in the above table for Alliant Energy and WPL. Natural Gas-Fired Generation Project - IPL’s Marshalltown Generating Station - IPL is currently constructing Marshalltown, an approximate 650 MW natural gas-fired combined-cycle EGU. Construction began in 2014 and is expected to be completed in 2017. As of December 31, 2015 and 2014, Alliant Energy and IPL recorded capitalized expenditures for CWIP of $453 million and $188 million, and AFUDC of $24 million and $4 million, respectively, for Marshalltown in “Construction work in progress” in the above table for Alliant Energy and IPL. Sales of IPL’s Minnesota Electric and Natural Gas Distribution Assets - In April 2015, IPL completed the sale of its Minnesota natural gas distribution assets (primarily related to property, plant and equipment) to Minnesota Energy Resources Corporation, a subsidiary of Integrys Energy Group, Inc. IPL received proceeds of $11 million and a promissory note of $2 million. In July 2015, IPL completed the sale of its Minnesota electric distribution assets (primarily related to property, plant and equipment) to Southern Minnesota Energy Cooperative, a combined group of various neighboring electric cooperatives, and received proceeds of $129 million. The proceeds from the natural gas distribution assets were used for general corporate purposes and the proceeds from the electric distribution assets were used to reduce cash amounts received from IPL’s sales of accounts receivable program. The premium received over the book value of the property, plant and equipment sold was more than offset by a reduction in tax-related regulatory assets associated with the distribution assets. As a result, Alliant Energy and IPL recorded pre-tax charges of $11 million and $3 million for the Minnesota electric and natural gas distribution asset transactions, respectively, in “Other operation and maintenance” in their income statements in 2015. The electric distribution asset sales agreement includes a wholesale power supply agreement between IPL and Southern Minnesota Energy Cooperative, which was approved by FERC in July 2015 and became effective upon the sale of IPL’s Minnesota electric distribution assets. The wholesale power supply agreement contains a five-year termination notice, which may not be given until the fifth anniversary of the effective date of the agreement, resulting in a minimum term of 10 years. The agreement remains in effect indefinitely, unless notice to terminate is provided by either party. This wholesale power supply agreement includes standardized pricing mechanisms that are detailed in IPL’s current tariffs accepted by FERC through wholesale rate case proceedings. IPL’s current return on common equity authorized by FERC related to its wholesale electric rates is 10.97%. As a result of IPL’s requirement to supply electricity to Southern Minnesota Energy Cooperative under the wholesale power supply agreement, the sale of the electric distribution assets did not have a significant impact on IPL’s generation plans or operating results. Refer to Note 19 for further discussion of IPL’s sales of its Minnesota electric and natural gas distribution assets. AFUDC - AFUDC represents costs to finance construction additions including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Equity |  | $24.4 |  |  |  | $23.1 |  |  |  | $20.3 |  |  |  | $18.6 |  |  |  | $17.1 |  |  |  | $13.8 |  |  |  | $5.8 |  |  |  | $6.0 |  |  |  | $6.5 |
Debt | 12.5 |  |  | 11.7 |  |  | 10.5 |  |  | 9.6 |  |  | 8.8 |  |  | 7.2 |  |  | 2.9 |  |  | 2.9 |  |  | 3.3 |
|  | $36.9 |  |  |  | $34.8 |  |  |  | $30.8 |  |  |  | $28.2 |  |  |  | $25.9 |  |  |  | $21.0 |  |  |  | $8.7 |  |  |  | $8.9 |  |  |  | $9.8 |
AFUDC related to various construction projects was recognized in the income statements as follows (in millions):
| 2015 |  | 2014 |  | 2013
IPL: |  |  |  |  |
Marshalltown |  | $20.7 |  |  |  | $3.7 |  |  |  | $— |
Environmental controls - Ottumwa Unit 1 | — |  |  | 10.6 |  |  | 8.0 |
Environmental controls - George Neal Units 3 and 4 | — |  |  | 1.4 |  |  | 5.1 |
Other | 7.5 |  |  | 10.2 |  |  | 7.9 |
| 28.2 |  |  | 25.9 |  |  | 21.0 |
WPL: |  |  |  |  |
Environmental controls - Edgewater Unit 5 | 5.1 |  |  | 2.7 |  |  | — |
Environmental controls - Columbia Units 1 and 2 | — |  |  | 4.0 |  |  | 7.2 |
Other | 3.6 |  |  | 2.2 |  |  | 2.6 |
| 8.7 |  |  | 8.9 |  |  | 9.8 |
Alliant Energy |  | $36.9 |  |  |  | $34.8 |  |  |  | $30.8 |
In 2014, scrubbers and baghouses were placed in service at IPL’s Ottumwa Unit 1 and George Neal Unit 3, and WPL’s Columbia Units 1 and 2. In 2013, a scrubber and baghouse was placed in service at IPL’s George Neal Unit 4.
WPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | PROPERTY, PLANT AND EQUIPMENT At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
In service: |  |  |  |  |  |  |  |  |  |  |
Generation |  | $5,643.7 |  |  |  | $5,463.0 |  |  |  | $3,011.6 |  |  |  | $2,872.4 |  |  |  | $2,632.1 |  |  |  | $2,590.6 |
Distribution | 4,489.9 |  |  | 4,435.4 |  |  | 2,447.9 |  |  | 2,471.7 |  |  | 2,042.0 |  |  | 1,963.7 |
Other | 311.3 |  |  | 309.1 |  |  | 212.2 |  |  | 215.5 |  |  | 99.1 |  |  | 93.6 |
Anticipated to be retired early (a) | — |  |  | 157.6 |  |  | — |  |  | — |  |  | — |  |  | 157.6 |
Total electric plant | 10,444.9 |  |  | 10,365.1 |  |  | 5,671.7 |  |  | 5,559.6 |  |  | 4,773.2 |  |  | 4,805.5 |
Gas plant in service | 1,018.3 |  |  | 946.2 |  |  | 513.6 |  |  | 474.0 |  |  | 504.7 |  |  | 472.2 |
Other plant in service | 530.6 |  |  | 539.3 |  |  | 296.0 |  |  | 298.8 |  |  | 234.6 |  |  | 240.5 |
Accumulated depreciation (a) | (3,939.6 | ) |  | (3,923.1 | ) |  | (2,152.8 | ) |  | (2,124.5 | ) |  | (1,786.8 | ) |  | (1,798.6 | )
Net plant | 8,054.2 |  |  | 7,927.5 |  |  | 4,328.5 |  |  | 4,207.9 |  |  | 3,725.7 |  |  | 3,719.6 |
Leased Sheboygan Falls Energy Facility, net (b) | — |  |  | — |  |  | — |  |  | — |  |  | 58.6 |  |  | 64.7 |
Construction work in progress | 897.5 |  |  | 479.1 |  |  | 578.2 |  |  | 325.0 |  |  | 319.3 |  |  | 154.1 |
Other, net | 18.5 |  |  | 22.3 |  |  | 18.4 |  |  | 21.8 |  |  | 0.1 |  |  | 0.5 |
Total utility | 8,970.2 |  |  | 8,428.9 |  |  | 4,925.1 |  |  | 4,554.7 |  |  | 4,103.7 |  |  | 3,938.9 |
Non-regulated and other: |  |  |  |  |  |  |  |  |  |  |
Non-regulated Generation, net (c) | 229.3 |  |  | 240.1 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (d) | 319.6 |  |  | 269.4 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-regulated and other | 548.9 |  |  | 509.5 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $9,519.1 |  |  |  | $8,938.4 |  |  |  | $4,925.1 |  |  |  | $4,554.7 |  |  |  | $4,103.7 |  |  |  | $3,938.9 |
(a) | In December 2015, WPL retired Nelson Dewey Units 1 and 2 and Edgewater Unit 3 and transferred the remaining net book value from property, plant and equipment to regulatory assets pursuant to orders from the PSCW and FERC. Refer to Note 2 for discussion of the recovery of the remaining net book value of these EGUs.
(b) | Less accumulated amortization of $65.2 million and $59.1 million for WPL as of December 31, 2015 and 2014, respectively.
(c) | Less accumulated depreciation of $59.0 million and $49.5 million for Alliant Energy as of December 31, 2015 and 2014, respectively.
(d) | Less accumulated depreciation of $252.9 million and $229.1 million for Alliant Energy as of December 31, 2015 and 2014, respectively.
Utility - Environmental Controls Project - WPL’s Edgewater Unit 5 - WPL is currently constructing a scrubber and baghouse at Edgewater Unit 5. The scrubber and baghouse reduce SO2 and mercury emissions at the EGU and are expected to help meet requirements under the MATS Rule and CSAPR. Construction began in 2014 and is expected to be completed in 2016. As of December 31, 2015 and 2014, Alliant Energy and WPL recorded capitalized expenditures for CWIP of $190 million and $90 million, and AFUDC of $8 million and $3 million, respectively, for the scrubber and baghouse in “Construction work in progress” in the above table for Alliant Energy and WPL. Natural Gas-Fired Generation Project - IPL’s Marshalltown Generating Station - IPL is currently constructing Marshalltown, an approximate 650 MW natural gas-fired combined-cycle EGU. Construction began in 2014 and is expected to be completed in 2017. As of December 31, 2015 and 2014, Alliant Energy and IPL recorded capitalized expenditures for CWIP of $453 million and $188 million, and AFUDC of $24 million and $4 million, respectively, for Marshalltown in “Construction work in progress” in the above table for Alliant Energy and IPL. Sales of IPL’s Minnesota Electric and Natural Gas Distribution Assets - In April 2015, IPL completed the sale of its Minnesota natural gas distribution assets (primarily related to property, plant and equipment) to Minnesota Energy Resources Corporation, a subsidiary of Integrys Energy Group, Inc. IPL received proceeds of $11 million and a promissory note of $2 million. In July 2015, IPL completed the sale of its Minnesota electric distribution assets (primarily related to property, plant and equipment) to Southern Minnesota Energy Cooperative, a combined group of various neighboring electric cooperatives, and received proceeds of $129 million. The proceeds from the natural gas distribution assets were used for general corporate purposes and the proceeds from the electric distribution assets were used to reduce cash amounts received from IPL’s sales of accounts receivable program. The premium received over the book value of the property, plant and equipment sold was more than offset by a reduction in tax-related regulatory assets associated with the distribution assets. As a result, Alliant Energy and IPL recorded pre-tax charges of $11 million and $3 million for the Minnesota electric and natural gas distribution asset transactions, respectively, in “Other operation and maintenance” in their income statements in 2015. The electric distribution asset sales agreement includes a wholesale power supply agreement between IPL and Southern Minnesota Energy Cooperative, which was approved by FERC in July 2015 and became effective upon the sale of IPL’s Minnesota electric distribution assets. The wholesale power supply agreement contains a five-year termination notice, which may not be given until the fifth anniversary of the effective date of the agreement, resulting in a minimum term of 10 years. The agreement remains in effect indefinitely, unless notice to terminate is provided by either party. This wholesale power supply agreement includes standardized pricing mechanisms that are detailed in IPL’s current tariffs accepted by FERC through wholesale rate case proceedings. IPL’s current return on common equity authorized by FERC related to its wholesale electric rates is 10.97%. As a result of IPL’s requirement to supply electricity to Southern Minnesota Energy Cooperative under the wholesale power supply agreement, the sale of the electric distribution assets did not have a significant impact on IPL’s generation plans or operating results. Refer to Note 19 for further discussion of IPL’s sales of its Minnesota electric and natural gas distribution assets. AFUDC - AFUDC represents costs to finance construction additions including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013 |  | 2015 |  | 2014 |  | 2013
Equity |  | $24.4 |  |  |  | $23.1 |  |  |  | $20.3 |  |  |  | $18.6 |  |  |  | $17.1 |  |  |  | $13.8 |  |  |  | $5.8 |  |  |  | $6.0 |  |  |  | $6.5 |
Debt | 12.5 |  |  | 11.7 |  |  | 10.5 |  |  | 9.6 |  |  | 8.8 |  |  | 7.2 |  |  | 2.9 |  |  | 2.9 |  |  | 3.3 |
|  | $36.9 |  |  |  | $34.8 |  |  |  | $30.8 |  |  |  | $28.2 |  |  |  | $25.9 |  |  |  | $21.0 |  |  |  | $8.7 |  |  |  | $8.9 |  |  |  | $9.8 |
AFUDC related to various construction projects was recognized in the income statements as follows (in millions):
| 2015 |  | 2014 |  | 2013
IPL: |  |  |  |  |
Marshalltown |  | $20.7 |  |  |  | $3.7 |  |  |  | $— |
Environmental controls - Ottumwa Unit 1 | — |  |  | 10.6 |  |  | 8.0 |
Environmental controls - George Neal Units 3 and 4 | — |  |  | 1.4 |  |  | 5.1 |
Other | 7.5 |  |  | 10.2 |  |  | 7.9 |
| 28.2 |  |  | 25.9 |  |  | 21.0 |
WPL: |  |  |  |  |
Environmental controls - Edgewater Unit 5 | 5.1 |  |  | 2.7 |  |  | — |
Environmental controls - Columbia Units 1 and 2 | — |  |  | 4.0 |  |  | 7.2 |
Other | 3.6 |  |  | 2.2 |  |  | 2.6 |
| 8.7 |  |  | 8.9 |  |  | 9.8 |
Alliant Energy |  | $36.9 |  |  |  | $34.8 |  |  |  | $30.8 |
In 2014, scrubbers and baghouses were placed in service at IPL’s Ottumwa Unit 1 and George Neal Unit 3, and WPL’s Columbia Units 1 and 2. In 2013, a scrubber and baghouse was placed in service at IPL’s George Neal Unit 4.

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