| Schedule of Property Plant and Equipment |
The service life ranges and weighted average remaining service life of PPE as at December 31 were as follows. | | | | | | | | | | | | | | | | | | | | | | | 2024 | 2023 | | (years) | Service Life Ranges | Weighted Average Remaining Service Life | | Service Life Ranges | Weighted Average Remaining Service Life | | Distribution | | | | | | | Electric | 5-80 | 32 | | 5-80 | 31 | | Gas | 18-83 | 37 | | 18-95 | 38 | | Transmission | | | | | | | Electric | 20-85 | 42 | | 20-90 | 41 | | Gas | 10-80 | 35 | | 10-85 | 36 | | Generation | 2-95 | 22 | | 2-95 | 23 | | Other | 3-80 | 13 | | 3-80 | 10 |
| | | | | | | | | | | | | | | | | | | | | | ($ millions) | Cost | | Accumulated Depreciation | | Net Book Value | | 2024 | | | | | | | Distribution | | | | | | | Electric | 15,771 | | | (4,078) | | | 11,693 | | | Gas | 7,148 | | | (1,866) | | | 5,282 | | | Transmission | | | | | | | Electric | 23,084 | | | (4,865) | | | 18,219 | | | Gas | 2,937 | | | (894) | | | 2,043 | | | Generation | 8,056 | | | (3,110) | | | 4,946 | | | Other | 5,014 | | | (1,809) | | | 3,205 | | | Assets under construction | 3,578 | | | — | | | 3,578 | | | Land | 490 | | | — | | | 490 | | | | 66,078 | | | (16,622) | | | 49,456 | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 2023 | | | Distribution | | | | | | | Electric | 14,352 | | | (3,708) | | | 10,644 | | | Gas | 6,682 | | | (1,736) | | | 4,946 | | | Transmission | | | | | | | Electric | 19,886 | | | (4,267) | | | 15,619 | | | Gas | 2,751 | | | (843) | | | 1,908 | | | Generation | 7,192 | | | (2,739) | | | 4,453 | | | Other | 4,444 | | | (1,645) | | | 2,799 | | | Assets under construction | 2,581 | | | — | | | 2,581 | | | Land | 435 | | | — | | | 435 | | | | 58,323 | | | (14,938) | | | 43,385 | |
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| Schedule of Jointly-Owned Facilities |
As at December 31, 2024, interests in jointly owned facilities consisted of the following. | | | | | | | | | | | | | | | | | | | | | | | | | Ownership | | | | Accumulated | | Net Book | | ($ millions, except as indicated) | (%) | | Cost | | Depreciation | | Value | | Transmission Facilities | Various | | 1,704 | | | (489) | | | 1,215 | | | Springerville Common Facilities | 86.0 | | | 580 | | | (344) | | | 236 | | | | | | | | | | | Springerville Coal Handling Facilities | 83.0 | | | 299 | | | (154) | | | 145 | | | Four Corners Units 4 and 5 ("Four Corners") | 7.0 | | | 311 | | | (155) | | | 156 | | | Gila River Common Facilities | 50.0 | | | 131 | | | (52) | | | 79 | | | Luna Energy Facility ("Luna") | 33.3 | | | 101 | | | 3 | | | 104 | | | | | 3,126 | | | (1,191) | | | 1,935 | |
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