| Selected Balance Sheet Data |
3. Selected Balance Sheet Data
(Thousands of Dollars) | | Sept. 30, 2012 | | | Dec. 31, 2011 | | Accounts receivable, net | | | | | | | Accounts receivable | | $ | 89,009 | | | $ | 70,410 | | Less allowance for bad debts | | | (4,938 | ) | | | (5,380 | ) | | | | $ | 84,071 | | | $ | 65,030 | |
| | | | | | | | (Thousands of Dollars) | | Sept. 30, 2012 | | | Dec. 31, 2011 | | Inventories | | | | | | | Materials and supplies | | $ | 19,022 | | | $ | 17,472 | | Fuel | | | 12,952 | | | | 18,103 | | | | | $ | 31,974 | | | $ | 35,575 | |
| | | | | | | | (Thousands of Dollars) | | Sept. 30, 2012 | | | Dec. 31, 2011 | | Property, plant and equipment, net | | | | | | | Electric plant | | $ | 4,344,849 | | | $ | 4,142,389 | | Construction work in progress | | | 199,459 | | | | 153,672 | | Total property, plant and equipment | | | 4,544,308 | | | | 4,296,061 | | Less accumulated depreciation | | | (1,758,904 | ) | | | (1,701,329 | ) | | | | $ | 2,785,404 | | | $ | 2,594,732 | |
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