| 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. | | | | | | | | | | | | | | | | | | | | | | | 2023 | 2022 | | (years) | Service Life Ranges | Weighted Average Remaining Service Life | | Service Life Ranges | Weighted Average Remaining Service Life | | Distribution | | | | | | | Electric | 5-80 | 31 | | 5-80 | 31 | | Gas | 18-95 | 38 | | 18-95 | 39 | | Transmission | | | | | | | Electric | 20-90 | 41 | | 20-90 | 41 | | Gas | 10-85 | 36 | | 10-85 | 35 | | Generation | 2-95 | 23 | | 5-95 | 22 | | Other | 3-80 | 10 | | 3-80 | 11 |
| | | | | | | | | | | | | | | | | | | | | | ($ millions) | Cost | | Accumulated Depreciation | | Net Book Value | | 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 | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 2022 | | | Distribution | | | | | | | Electric | 13,650 | | | (3,715) | | | 9,935 | | | Gas | 6,396 | | | (1,626) | | | 4,770 | | | Transmission | | | | | | | Electric | 19,056 | | | (4,074) | | | 14,982 | | | Gas | 2,600 | | | (800) | | | 1,800 | | | Generation | 7,173 | | | (2,679) | | | 4,494 | | | Other | 4,803 | | | (1,610) | | | 3,193 | | | Assets under construction | 2,094 | | | — | | | 2,094 | | | Land | 395 | | | — | | | 395 | | | | 56,167 | | | (14,504) | | | 41,663 | |
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| Schedule of Jointly-Owned Facilities |
As at December 31, 2023, interests in jointly owned facilities consisted of the following. | | | | | | | | | | | | | | | | | | | | | | | | | Ownership | | | | Accumulated | | Net Book | | ($ millions, except as indicated) | (%) | | Cost | | Depreciation | | Value | | Transmission Facilities | Various | | 1,485 | | | (432) | | | 1,053 | | | Springerville Common Facilities | 86.0 | | | 530 | | | (302) | | | 228 | | | | | | | | | | | Springerville Coal Handling Facilities | 83.0 | | | 275 | | | (136) | | | 139 | | | Four Corners Units 4 and 5 ("Four Corners") | 7.0 | | | 271 | | | (128) | | | 143 | | | Gila River Common Facilities | 50.0 | | | 119 | | | (45) | | | 74 | | | Luna Energy Facility ("Luna") | 33.3 | | | 81 | | | — | | | 81 | | | | | 2,761 | | | (1,043) | | | 1,718 | |
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