Onahama power station is a 400 MW coal power station in Fukushima Prefecture, Japan. It is operated by Diamond Power Corp [100%]. Based on its capacity (estimated), it can supply roughly 501k homes (estimated). It ranks #160 of 692 Japan power plants by installed capacity. In context, coal supplies about 32.1% of Japan's electricity; the national grid averages 477 gCO₂/kWh (32.7% low-carbon) (2025).
Plant data: WRI Global Power Plant Database (CC BY 4.0), id GEM_coa_onahama_japan.
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: GEM GCPT; fuel: GEM GCPT
At 400 MW, Onahama power station is well above the median coal plant in Japan (250 MW). Technically it is described as subcritical. Coal plants burn pulverised coal to raise high-pressure steam for a turbine; they run as baseload but are the most carbon-intensive mainstream source and the first targeted for retirement or efficiency retrofits.
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 Diamond Power Corp [100%].
This coal plant burns coal to raise high-pressure steam that spins a turbine-generator. It sits in a humid subtropical climate (Köppen Cfa) — Northern Hemisphere, latitude 36.9°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 12% below 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: 46/100 — this site sits in the mid 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 corrosive environment (estimated ISO 9223 class C4 — High), 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 #35 largest coal power plant of 94 in Japan by capacity.
Japan has 94 coal power plants in this dataset, together about 53,431 MW of capacity.
Coordinates 36.947785, 140.893703 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.
Onahama power station is a 400 MW coal power plant in Fukushima Prefecture, Japan.
Its output is enough to supply roughly 500,571 homes (estimated).
Onahama power station is operated by Diamond Power Corp [100%].
