Note 9 - Property, Plant and Equipment and Construction-in-process (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Property, Plant and Equipment [Table Text Block]

	December 31,
	2022			2021
	(Dollars in thousands)
Land owned by the Company where the geothermal resource is located	$	42,335		$	40,545
Leasehold improvements		13,230			9,105
Machinery and equipment		350,584			302,367
Land, buildings and office equipment		52,222			48,275
Vehicles		14,115			10,724
Energy storage equipment		91,025			79,805
Solar facility equipment		32,003			—
Geothermal and recovered energy generation power plants, including geothermal wells and exploration and resource development costs:
United States of America, net of cash grants		2,641,280			2,511,027
Foreign countries		897,657			800,000
Asset retirement cost		48,578			41,157
		4,183,029			3,843,005
Less accumulated depreciation		(1,689,572	)		(1,548,032	)
Property, plant and equipment, net	$	2,493,457		$	2,294,973

Construction In Progress [Table Text Block]

	December 31,
	2022		2021
	(Dollars in thousands)
Projects under exploration and development:
Up-front bonus costs	$	5,335	$	5,335
Exploration and development costs		89,230		44,664
Interest capitalized		703		703
		95,268		50,702
Projects under construction:
Up-front bonus costs		11,156		39,156
Drilling and construction costs		761,129		611,553
Interest capitalized		25,645		20,072
		797,930		670,781
Total	$	893,198	$	721,483

Rollforward Of Construction In Process [Table Text Block]

	Projects under exploration and development
	Up-front Bonus Costs			Exploration and Development Costs			Interest Capitalized		Total
	(Dollars in thousands)
Balance at December 31, 2019	$	17,018		$	66,916		$	703	$	84,637
Cost incurred during the year		—			5,832			—		5,832
Transfer of projects under exploration and development to projects under construction		(11,671	)		(27,270	)		—		(38,941	)
Balance at December 31, 2020		5,347			45,478			703		51,528
Cost incurred during the year		—			2,680			—		2,680
Transfer of projects under exploration and development to projects under construction		(12	)		(3,494	)		—		(3,506	)
Balance at December 31, 2021		5,335			44,664			703		50,702
Cost incurred during the year		—			44,566			—		44,566
Balance at December 31, 2022	$	5,335		$	89,230		$	703	$	95,268

	Projects under construction
	Up-front Bonus Costs			Drilling and Construction Costs			Interest Capitalized		Total
	(Dollars in thousands)
Balance at December 31, 2019	$	27,473		$	258,484		$	5,961	$	291,918
Cost incurred during the year		—			298,215			3,565		301,780
Transfer of projects under exploration and development to projects under construction		11,671			27,270			—		38,941
Transfer of completed projects to property, plant and equipment		—			(204,852	)		—		(204,852	)
Balance at December 31, 2020		39,144			379,117			9,526		427,787
Cost incurred during the year		—			403,296			10,546		413,842
Transfer of projects under exploration and development to projects under construction		12			3,494			—		3,506
Transfer of completed projects to property, plant and equipment		—			(174,354	)		—		(174,354	)
Balance at December 31, 2021		39,156			611,553			20,072		670,781
Cost incurred during the year		—			489,953			5,573		495,526
Transfer of completed projects to property, plant and equipment		(28,000	)		(340,377	)		—		(368,377	)
Balance at December 31, 2022	$	11,156		$	761,129		$	25,645	$	797,930

North Brawley Geothermal Power Plant [Member]

Notes Tables

Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

Significant unobservable inputs:
Average generation capacity (MW)	7
Electricity price escalation (%)	2.2
Cost long-term growth rate	2.2
Average realized electricity price ($/MW)	92.2