Depreciation of utility plant is computed based on the estimated useful lives as follows:
Useful Lives
Equipment
3 to 30 years
Office buildings and other structures
30 years
Transmission and distribution plant
10 to 50 years
Utility plant as of December 31, 2024 and 2023 consist of the following (in thousands):
December 31, 2024December 31, 2023
Transmission and distribution plant$321,075 $290,247 
Equipment67,917 60,536 
Office buildings and other structures67,313 64,084 
Construction work-in-progress54,388 48,147 
Land2,300 2,674 
Total utility plant$512,993 $465,688 

Historical Timeline

Fiscal YearFiled
2024Mar 5, 2025Showing above
2023Mar 7, 2024
2022Mar 9, 2023
2021Mar 10, 2022
2020Mar 4, 2021
2019Mar 5, 2020
2018Mar 7, 2019
2017Mar 9, 2018
2016Mar 10, 2017

About PP&E Disclosures

The PP&E disclosure details a company's physical asset base — land, buildings, machinery, and equipment — along with the depreciation methods and useful life assumptions that determine how these costs flow through the income statement. Capitalization policy thresholds reveal management's judgment on the boundary between expense and asset, directly affecting both reported earnings and asset values.

Key signals: changes in estimated useful lives or depreciation methods can materially shift reported earnings without any operational change. Compare capital expenditures against depreciation expense — when capex consistently trails depreciation, the asset base may be aging and underinvested. Watch for large asset impairments or write-downs that signal overvalued carrying amounts. Asset retirement obligations reveal future environmental or decommissioning costs that are often underappreciated. Compare PP&E intensity (PP&E-to-revenue) against industry peers to assess capital efficiency and competitive positioning.