- By 1940, CEA membership climbs to 793.
- Edmonton's 330 MW Rossdale Generating Station, with six coal-fired steam turbine sets, becomes Canada's largest thermal power plant. It is converted to natural gas in the 1950s.
- The Québec Hydro-Electric Commission (later Hydro-Québec) is formed in 1944 by expropriating investor-owned utilities. Today, it is one of North America's largest utilities.
- By 1948, 93 per cent of Newfoundland's electricity is consumed by the pulp and paper industry.
- Saskatchewan passes its Rural Electrification Act in 1949. By 1960, 67,000 farms and all villages in the populated half of the province are electrified.
- In 1951, Canada's first 100 MW steam turbo-generator set goes into service at the Richard L. Hearn plant in Toronto.
- Atomic Energy Canada Limited is formed in 1952.
- Preliminary studies begin on Canada's first nuclear power plant in 1953. Construction begins the following year, with electricity fed into Ontario Hydro's grid on June 4, 1962.
- In 1956, following seven years of work, Hydro-Québec
- completes one of its first megaprojects, the Bersimis I Hydro Generation Station.
- In 1957, B.C. Electric is Canada's first utility to build a 360 kV transmission line.