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SEGMENT INFORMATION (Details) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 USD ($) | Jun. 30, 2021 USD ($) | Mar. 31, 2021 USD ($) | Sep. 30, 2020 USD ($) | Jun. 30, 2020 USD ($) | Mar. 31, 2020 USD ($) | Sep. 30, 2021 USD ($) segment | Sep. 30, 2020 USD ($)
Segment information |  |  |  |  |  |  |  |
Number of reportable segments | segment |  |  |  |  |  |  | 6 |
Total operating revenues | $ 1,746.5 |  |  | $ 1,651.0 |  |  | $ 6,114.1 | $ 5,308.3
Other operation and maintenance | 473.7 |  |  | 498.7 |  |  | 1,417.4 | 1,427.5
Depreciation and amortization | 271.6 |  |  | 245.0 |  |  | 799.2 | 726.6
Equity in earnings of transmission affiliates | 42.3 |  |  | 40.1 |  |  | 126.2 | 132.8
Interest expense | 118.0 |  |  | 122.0 |  |  | 357.5 | 375.8
Income tax expense (benefit) | 50.8 |  |  | 46.9 |  |  | 179.8 | 190.7
Net income (loss) | 288.7 |  |  | 267.1 |  |  | 1,074.7 | 961.8
Net income (loss) attributed to common shareholders | 290.0 | $ 276.0 | $ 510.1 | 266.8 | $ 241.6 | $ 452.5 | 1,076.1 | 960.9
External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 1,746.5 |  |  | 1,651.0 |  |  | 6,114.1 | 5,308.3
Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Utility Operations |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Other operation and maintenance | 469.9 |  |  | 493.4 |  |  | 1,402.4 | 1,413.0
Depreciation and amortization | 249.4 |  |  | 228.1 |  |  | 730.7 | 673.3
Equity in earnings of transmission affiliates | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Interest expense | 156.0 |  |  | 157.4 |  |  | 472.0 | 477.3
Income tax expense (benefit) | 39.6 |  |  | 32.3 |  |  | 177.4 | 166.9
Net income (loss) | 214.2 |  |  | 197.6 |  |  | 800.5 | 743.2
Net income (loss) attributed to common shareholders | 213.9 |  |  | 197.3 |  |  | 799.6 | 742.3
Utility Operations | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 1,727.6 |  |  | 1,636.5 |  |  | 6,051.1 | 5,263.5
Utility Operations | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Reconciling Eliminations |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Other operation and maintenance | (1.6) |  |  | (1.6) |  |  | (7.1) | (7.1)
Depreciation and amortization | (15.3) |  |  | (14.1) |  |  | (44.3) | (39.1)
Equity in earnings of transmission affiliates | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Interest expense | (85.1) |  |  | (85.7) |  |  | (256.0) | (259.6)
Income tax expense (benefit) | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Net income (loss) | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Net income (loss) attributed to common shareholders | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Reconciling Eliminations | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Reconciling Eliminations | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | $ (110.8) |  |  | (109.6) |  |  | $ (338.0) | (335.6)
ATC Holdco |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Equity method investment, ownership interest (as a percent) | 75.00% |  |  |  |  |  | 75.00% |
Equity in earnings of transmission affiliates | $ 0.6 |  |  | 0.5 |  |  | $ 2.1 | 1.1
Wisconsin |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 1,458.6 |  |  | 1,366.3 |  |  | 4,497.8 | 4,071.4
Wisconsin | Utility Operations |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Other operation and maintenance | 359.1 |  |  | 363.8 |  |  | 1,047.1 | 1,044.0
Depreciation and amortization | 184.4 |  |  | 169.7 |  |  | 540.4 | 502.7
Equity in earnings of transmission affiliates | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Interest expense | 137.9 |  |  | 139.1 |  |  | 417.8 | 422.2
Income tax expense (benefit) | 33.6 |  |  | 37.5 |  |  | 104.8 | 110.5
Net income (loss) | 197.8 |  |  | 187.9 |  |  | 601.2 | 565.0
Net income (loss) attributed to common shareholders | 197.5 |  |  | 187.6 |  |  | 600.3 | 564.1
Wisconsin | Utility Operations | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 1,458.6 |  |  | 1,366.3 |  |  | 4,497.8 | 4,071.4
Wisconsin | Utility Operations | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Illinois |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 216.2 |  |  | 221.9 |  |  | 1,195.1 | 930.7
Illinois | Utility Operations |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Other operation and maintenance | 91.2 |  |  | 109.2 |  |  | 291.3 | 306.5
Depreciation and amortization | 55.4 |  |  | 49.9 |  |  | 162.1 | 146.0
Equity in earnings of transmission affiliates | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Interest expense | 16.5 |  |  | 15.6 |  |  | 49.6 | 47.7
Income tax expense (benefit) | 7.0 |  |  | (4.0) |  |  | 64.4 | 47.7
Net income (loss) | 19.1 |  |  | 13.0 |  |  | 174.8 | 152.4
Net income (loss) attributed to common shareholders | 19.1 |  |  | 13.0 |  |  | 174.8 | 152.4
Illinois | Utility Operations | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 216.2 |  |  | 221.9 |  |  | 1,195.1 | 930.7
Illinois | Utility Operations | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Other States |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 52.8 |  |  | 48.3 |  |  | 358.2 | 261.4
Other States | Utility Operations |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Other operation and maintenance | 19.6 |  |  | 20.4 |  |  | 64.0 | 62.5
Depreciation and amortization | 9.6 |  |  | 8.5 |  |  | 28.2 | 24.6
Equity in earnings of transmission affiliates | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Interest expense | 1.6 |  |  | 2.7 |  |  | 4.6 | 7.4
Income tax expense (benefit) | (1.0) |  |  | (1.2) |  |  | 8.2 | 8.7
Net income (loss) | (2.7) |  |  | (3.3) |  |  | 24.5 | 25.8
Net income (loss) attributed to common shareholders | (2.7) |  |  | (3.3) |  |  | 24.5 | 25.8
Other States | Utility Operations | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 52.8 |  |  | 48.3 |  |  | 358.2 | 261.4
Other States | Utility Operations | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Electric Transmission |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Other operation and maintenance | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Depreciation and amortization | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Equity in earnings of transmission affiliates | 42.3 |  |  | 40.1 |  |  | 126.2 | 132.8
Interest expense | 4.8 |  |  | 4.9 |  |  | 14.5 | 14.6
Income tax expense (benefit) | 9.7 |  |  | 9.0 |  |  | 28.9 | 33.4
Net income (loss) | 27.8 |  |  | 26.3 |  |  | 82.8 | 84.8
Net income (loss) attributed to common shareholders | 27.8 |  |  | 26.3 |  |  | 82.8 | 84.8
Electric Transmission | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Electric Transmission | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | $ 0.0 |  |  | 0.0 |  |  | $ 0.0 | 0.0
Electric Transmission | ATC |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Equity method investment, ownership interest (as a percent) | 60.00% |  |  |  |  |  | 60.00% |
Electric Transmission | ATC Holdco |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Equity method investment, ownership interest (as a percent) | 75.00% |  |  |  |  |  | 75.00% |
Non-Utility Energy Infrastructure |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Natural gas storage needs provided to Wisconsin utilities |  |  |  |  |  |  | 33.00% |
Total operating revenues | $ 129.5 |  |  | 123.5 |  |  | $ 400.6 | 378.4
Other operation and maintenance | 9.9 |  |  | 5.9 |  |  | 31.2 | 18.7
Depreciation and amortization | 31.2 |  |  | 24.5 |  |  | 93.5 | 73.4
Equity in earnings of transmission affiliates | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Interest expense | 17.6 |  |  | 15.0 |  |  | 53.5 | 45.4
Income tax expense (benefit) | 5.0 |  |  | 13.4 |  |  | 5.8 | 35.8
Net income (loss) | 62.8 |  |  | 62.9 |  |  | 202.3 | 193.2
Net income (loss) attributed to common shareholders | 64.4 |  |  | 62.9 |  |  | 204.6 | 193.2
Non-Utility Energy Infrastructure | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 18.7 |  |  | 13.9 |  |  | 62.6 | 42.8
Non-Utility Energy Infrastructure | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | $ 110.8 |  |  | 109.6 |  |  | $ 338.0 | 335.6
Non-Utility Energy Infrastructure | Bishop Hill III |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
WEC's ownership interest | 90.00% |  |  |  |  |  | 90.00% |
Non-Utility Energy Infrastructure | Coyote Ridge |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
WEC's ownership interest | 80.00% |  |  |  |  |  | 80.00% |
Non-Utility Energy Infrastructure | Upstream |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
WEC's ownership interest | 90.00% |  |  |  |  |  | 90.00% |
Non-Utility Energy Infrastructure | Blooming Grove |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
WEC's ownership interest | 90.00% |  |  |  |  |  | 90.00% |
Non-Utility Energy Infrastructure | Tatanka Ridge |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
WEC's ownership interest | 85.00% |  |  |  |  |  | 85.00% |
Non-Utility Energy Infrastructure | JayhawkWindLLC |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
WEC's ownership interest | 90.00% |  |  |  |  |  | 90.00% |
Corporate and Other |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | $ 0.2 |  |  | 0.6 |  |  | $ 0.4 | 2.0
Other operation and maintenance | (4.5) |  |  | 1.0 |  |  | (9.1) | 2.9
Depreciation and amortization | 6.3 |  |  | 6.5 |  |  | 19.3 | 19.0
Equity in earnings of transmission affiliates | 0.0 |  |  | 0.0 |  |  | 0.0 | 0.0
Interest expense | 24.7 |  |  | 30.4 |  |  | 73.5 | 98.1
Income tax expense (benefit) | (3.5) |  |  | (7.8) |  |  | (32.3) | (45.4)
Net income (loss) | (16.1) |  |  | (19.7) |  |  | (10.9) | (59.4)
Net income (loss) attributed to common shareholders | (16.1) |  |  | (19.7) |  |  | (10.9) | (59.4)
Corporate and Other | External Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | 0.2 |  |  | 0.6 |  |  | 0.4 | 2.0
Corporate and Other | Intersegment Revenues |  |  |  |  |  |  |  |
Segment information |  |  |  |  |  |  |  |
Total operating revenues | $ 0.0 |  |  | $ 0.0 |  |  | $ 0.0 | $ 0.0

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