Merrimack — United States of America

Merrimack is a 496.4 MW coal power station in New Hampshire, United States of America. It is operated by Granite Shore Power. Based on reported annual generation of 302 GWh, it can supply roughly 86k homes. It ranks #1233 of 10,884 United States of America power plants by installed capacity. Commissioned in 1966, it is around 60 years old — an older, legacy facility. In context, coal supplies about 16.3% of United States of America's electricity; the national grid averages 384 gCO₂/kWh (43.0% low-carbon) (2025).

Plant data: WRI Global Power Plant Database (CC BY 4.0), id USA0002364.

Data provenance

Source of the capacity and fuel values:

capacity: Wikidata P2109; fuel: WRI GPPD

In context: how this plant compares

At 496.4 MW, Merrimack is below the median coal plant in United States of America (558 MW). 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.

Key facts

Load factor

7%, from 302 GWh of reported generation; the median for 244 coal plants in United States of America that report generation is 41%

Generation trend

1,319 GWh in 2013 and 302 GWh in 2019 (−77%)

Highest and lowest year

2013: 1,319 GWh; 2017: 238 GWh

Share of United States of America coal capacity

less than 0.1% of 621,194 MW across 802 plants in this dataset

Age among peers

234 of 745 dated coal plants in United States of America are older

Calculated from the capacity and generation records in this dataset (WRI Global Power Plant Database (CC BY 4.0)).

Reported generation trend

Annual generation (GWh), WRI Global Power Plant Database (CC BY 4.0).

Owner

Operated by Granite Shore Power.

Local climate & thermal context

This coal plant burns coal to raise high-pressure steam that spins a turbine-generator. It sits in a warm-summer humid continental climate (Köppen Dfb) — Northern Hemisphere, latitude 43.1°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 57% 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: 82/100 — 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.

Site climate & environmental severity

This site sits in a moderately corrosive environment (estimated ISO 9223 class C3 — Medium), with thermal cycling the leading environmental stress.

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.

How it compares & nearby plants

The #423 largest coal power plant of 802 in United States of America by capacity.

United States of America has 802 coal power plants in this dataset, together about 621,194 MW of capacity.

Nearby power plants

• Merrimack Station · Coal · 496.4 MW · New Hampshire
• China Mill Hydro · Hydro · 1.7 MW · New Hampshire
• Pembroke Hydro · Hydro · 2.7 MW · New Hampshire
• Garvins Falls · Hydro · 12.4 MW · New Hampshire
• Hooksett · Hydro · 1.6 MW · New Hampshire
• Amoskeag · Hydro · 16 MW · New Hampshire

Location

Coordinates 43.1411, -71.4692 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.

Frequently asked questions