TORONTO -- Bruce Power will spend $13 billion to refurbish six of the eight nuclear reactors at its generating station near Kincardine, Ont., and assume all risks for cost overruns.

The Liberal government announced Thursday that the agreement with Bruce will delay the start of the 15-year refurbishment project until 2020 from the original 2016 start date to squeeze more life out of the existing reactors.

Hydro consumers shouldn't be concerned about the four-year delay, because Bruce Power found "innovative ways" to extend the life of its nuclear reactors, said president and CEO Duncan Hawthorne.

"There is a very positive and immediate price impact for the ratepayer," he said. "Money spent later is obviously better for the price of power."

The agreement will save $1.7 billion dollars from the government's original plans, said Energy Minister Bob Chiarelli.

"Our updated agreement with Bruce Power secures 6,300 megawatts of emission-free, low-cost electricity supply," he said.

The price of electricity generated by Bruce increases to 6.57 cents a kilowatt hour Jan. 1, 2016, and rises as each reactor is refurbished to 7.7 a kwh cents by the end of the contract, or $77 per megawatt hour.

"That's less than the average price of power in Ontario today at $83 per megawatt hour...30 per cent lower than the residential rate," said Chiarelli. "So we're getting a hell of a bargain here in terms of price."

The government says the deal with Bruce will save the average household using 800 kilowatt hours a month of electricity about $66 a year.

If the refurbishments come in under budget, Bruce Power, which is owned in part by TransCanada Corp., would get a share of the savings.

Green Party Leader Mike Schreiner doubted six reactors could be refurbished for $13 billion because the contract is based on estimates of how much it will cost to do the work years in the future.

"We can't guarantee there will be no cost overruns passed onto ratepayers because we don't have a final price yet in the contract," said Schreiner.

"The fact that no nuclear project in Ontario's history has ever been delivered on budget or on time makes me think your pocket book is under threat."

The Progressive Conservatives called the announcement positive news following Wednesday's scathing auditor general's report that found Ontarians paid $37 billion more over eight years for the Liberal's electricity planning decisions.

"We've been calling for some clarity on nuclear refurbishment for some time," said PC energy critic John Yakabuski. "I am a little concerned about what's going to happen with Pickering and the number of reactors that could be out simultaneously."

All units at Ontario Power Generation's Pickering nuclear station will be retired by 2020, and the province also plans to refurbish some of the reactors at OPG's Darlington station starting near the end of 2016.

Both Hawthorne and Chiarelli said the agreement includes a specific schedule to stagger the work on the reactors to ensure an adequate supply of electricity.

The New Democrats want the Ontario Energy Board to review the agreement with Bruce to make sure the power is actually needed.

"Anyone who was there for the auditor general's report yesterday knows that simply leaving it up to the Liberal government to make a decision is not in the best interests of ratepayers," said NDP energy critic Peter Tabuns.

Greenpeace Canada called it foolish and risky to run some of the Bruce nuclear reactors 10 years past their original design life.

"The Liberals are delaying rebuilding the Bruce reactors to avoid the wearing the scandalous cost overruns that go with every nuclear project while they're in power," said Greenpeace spokesman Shawn-Patrick Stensil.