Cat Arm — Canada

Cat Arm is a 127 MW hydro power station in Newfoundland and Labrador, Canada. It is operated by Nalcor Energy [100%]. Based on its capacity (estimated), it can supply roughly 127k homes (estimated). It ranks #237 of 1,210 Canada power plants by installed capacity. Commissioned in 1985, it is around 41 years old — long-established. As a non-combustion source, it has no direct CO₂ emissions from generation. In context, hydro supplies about 52.8% of Canada's electricity; the national grid averages 191 gCO₂/kWh (77.0% low-carbon) (2025).

Plant data: WRI Global Power Plant Database (CC BY 4.0), id CAN0002121.

Data provenance

Source of the capacity and fuel values:

capacity: GEM · 2026 · L100000600421; fuel: WRI GPPD

In context: how this plant compares

At 127 MW, Cat Arm is well above the median hydro plant in Canada (12 MW). Technically it is described as conventional storage. Hydropower converts the energy of falling or flowing water into electricity; output depends on rainfall and reservoir level, and large dams also provide grid balancing and storage.

Capacity comparison computed from the WRI Global Power Plant Database; fuel-type context is general engineering background.

Key facts

Share of Canada hydro capacity

0.2% of 81,037 MW across 556 plants in this dataset

Age among peers

142 of 189 dated hydro plants in Canada are older

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

Capacity vs largest hydro plants in Canada

Installed capacity (MW), WRI Global Power Plant Database (CC BY 4.0).

Owner

Operated by Nalcor Energy [100%].

Local climate & thermal context

This hydro plant converts the energy of falling or flowing water through hydro turbines. It sits in a subarctic (boreal) climate (Köppen Dfc) — Northern Hemisphere, latitude 50.0°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 127% 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: 97/100 — 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 mild atmospheric environment (estimated ISO 9223 class C2 — Low), with humidity / wetness 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 #106 largest hydro power plant of 556 in Canada by capacity.

Canada has 556 hydro power plants in this dataset, together about 81,037 MW of capacity.

Nearby power plants

• Rattle Brook · Hydro · 4 MW · Newfoundland and Labrador
• Deer Lake · Hydro · 129 MW · Newfoundland and Labrador
• Hinds Lake · Hydro · 75 MW · Newfoundland and Labrador
• Buchans · Hydro · 1.8 MW · Newfoundland and Labrador
• Sandy Brook · Hydro · 5.5 MW · Newfoundland and Labrador
• Grand Falls · Hydro · 75 MW · Newfoundland and Labrador

Location

Coordinates 50.0258, -56.765 from WRI Global Power Plant Database (CC BY 4.0). View on OpenStreetMap.

Frequently asked questions