Onikobe is a 15 MW geothermal power plant in Miyagi, Japan. It is operated by TOHOKU ELECTRIC POWER CO. Based on its capacity (estimated), it can supply roughly 28k homes (estimated). It ranks #495 of 692 Japan power plants by installed capacity. Commissioned in 1975, it is around 51 years old — an older, legacy facility. As a non-combustion source, it has no direct CO₂ emissions from generation. In context, the national grid averages 477 gCO₂/kWh (32.7% low-carbon) (2025).
Plant data: WRI Global Power Plant Database (CC BY 4.0), id WRI1020122.
Known, modelled and calculated values are kept separate. Missing fields are shown as unavailable.
The capacity and fuel fields on this page are source-record values from the upstream open dataset. They are useful for identification and ranking, but they have not been upgraded to a 2026 registry/GEM-location verified value.
capacity: WRI Global Power Plant Database source-record (legacy); fuel: WRI source-record fuel
At 15 MW, Onikobe is below the median geothermal plant in Japan (30 MW). Geothermal plants tap underground heat to raise steam for a turbine; they provide steady, low-carbon baseload but are limited to geologically active regions.
Capacity comparison computed from the WRI Global Power Plant Database; fuel-type context is general engineering background.
Installed capacity (MW), WRI Global Power Plant Database (CC BY 4.0).
Operated by TOHOKU ELECTRIC POWER CO. All plants by this company →
This geothermal plant taps underground heat to raise steam that drives a turbine. It sits in a humid subtropical climate (Köppen Cfa) — Northern Hemisphere, latitude 38.8°N — which shapes how much energy it can produce and how its output varies through the year.
Monthly mean temperature
Heating degree-days here run 35% above the median power plant in this dataset — a proxy for how much extra energy heated equipment must replace through its surfaces in winter.
Climate heat-demand index: 71/100 — this site sits in the top third of the power plants we cover by heating degree-days.
Climate normals: WorldClim 2.1 (1970–2000 monthly normals, 10 arc-min, CC BY 4.0); zone: Köppen-Geiger world climate classification (Kottek et al. 2006, 0.5° grid). Degree-days & heat-demand index computed by PowerAtlas — a modelled heat-demand proxy, not a measured site figure.
For a plant’s outdoor hardware — heat-recovery steam generators (HRSG), expansion joints, valves, flanges and their insulation — the local climate sets how fast unprotected steel and coatings degrade. This site sits in a moderately corrosive environment (estimated ISO 9223 class C3 — Medium), with humidity / wetness the leading environmental stress.
Higher environmental severity is exactly where protective removable insulation pays back most: a sheltered micro-climate slows corrosion, UV and thermal-cycling damage and extends outdoor hardware service life. This is an indicative site-climate context — not a condition assessment of any specific plant or operator.
Indicative estimate via the ISO 9223:2012 informative method (atmospheric corrosivity from temperature, time-of-wetness and airborne salinity), using WorldClim climate normals, the Köppen-Geiger class and coast distance. Indicative, not a measured corrosion rate.
The #11 largest geothermal power plant of 14 in Japan by capacity.
Japan has 14 geothermal power plants in this dataset, together about 536 MW of capacity.
Coordinates 38.8098, 140.7086 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.
Onikobe is a 15 MW source-record geothermal power plant in Miyagi, Japan, commissioned in 1975.
Its output is enough to supply roughly 28,157 homes (estimated).
Onikobe is operated by TOHOKU ELECTRIC POWER CO.
