The other assets are depreciated using the straight-line method over the following estimated useful lives of the assets:
 
Years
Buildings 25
Leasehold improvements 15-30
Machinery and equipment — manufacturing and drilling 5-10
Machinery and equipment — computers 3-5
Energy storage equipment 8-20
Solar facility equipment30
Office equipment — furniture and fixtures 5-15
Office equipment — other5-10
Vehicles 5-7
 Property, plant and equipment, net, consist of the following:
December 31,
20252024
(Dollars in thousands)
Land owned by the Company where the geothermal resource is located $56,070 $51,500 
Leasehold improvements 18,311 12,746 
Machinery and equipment 419,231 389,252 
Buildings and office equipment
157,534 145,272 
Vehicles21,078 20,159 
Energy storage equipment522,610 324,065 
Solar facility equipment95,036 97,502 
Geothermal and recovered energy generation power plants, including geothermal wells and exploration and resource development costs:
United States of America, net of cash grants 3,708,110 3,585,209 
Foreign countries 959,613 919,680 
Asset retirement cost 54,002 59,831 
Total cost of property, plant and equipment
6,011,595 5,605,216 
Less accumulated depreciation (2,339,026)(2,103,330)
Property, plant and equipment, net $3,672,569 $3,501,886 

Historical Timeline

Fiscal YearFiled
2025Feb 26, 2026Showing above
2024Feb 27, 2025
2023Feb 23, 2024
2022Feb 24, 2023
2021Feb 25, 2022
2020Feb 26, 2021
2019Mar 2, 2020
2018Mar 1, 2019
2017Mar 16, 2018
2016Mar 1, 2017
2015Feb 26, 2016

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.