Ontario will defer indefinitely construction of two new nuclear-power reactors at the Darlington and Bruce Power facilities, scale back plans to refurbish operating units at those sites and may order the shutdown of another six-unit plant before its scheduled 2020 closing date, according to a long-term energy plan the provincial government released earlier this month.

The province said that advances in energy conservation, enhanced efficiency and a slowdown in electricity-demand growth prompted it to revise a 2010 energy plan that called for building the two new reactors at the Darlington powerplant site as well as refurbishing 10 units there and at a site owned by utility Bruce Power.

Ontario Power Generation owns the Darlington site. "This represents up to $15 billion in capital investments that are not currently required," the plan said. "The decision to defer new nuclear capacity helps manage electricity costs by making large investments only when needed."

Ontario says upgrades of two units at the Darlington and Bruce sites would begin in 2016, but it did not say when a decision would come on the others.

The plan projected nuclear's share of Ontario's electricity production would decline to around 40% in 2032 from about 60% this year.

During the same period,  It expects to have 10,700 MW on line by 2021.

But "Ontario continues to have the option to build new nuclear reactors in the future," the plan said. Candu Energy and Westinghouse submitted competing bids to build the Darlington reactors in late June, a year after Ontario Power requested the bids.

Maxim Sytchev, an E&C sector analyst for Dundee Capital Markets, says that Canadian-based engineering firms SNC-Lavalin and Aecon are set to benefit from the refurbishments because of past involvement at the sites and their expertise in energy design and construction in Canada.