TORONTO -- Homeowners who complete energy-efficient renovations will be eligible for thousands of dollars in rebates under a new program announced by Ontario's environment minister Wednesday.

Chris Ballard said the government will use $600 million over four years from cap-and-trade proceeds to establish the rebate program through a provincial agency called the Green Ontario Fund.

The program offers up to a $7,200 rebate for new insulation, up to $5,000 for new windows, and up to $20,000 for new ground source heat pumps.

"Those funds are being re-invested in programs like this where we're helping business, we're helping homeowners fight climate change and save money," Ballard said.

The program launched online Wednesday at GreenOn.ca. In order to access the rebates, homeowners must hire a contractor who has been screened by the Green Ontario Fund.

The new program comes after an August commitment to provide thousands of free smart thermostats to homeowners, a promise that Ballard acknowledged has rolled out more slowly than the government would have liked. Only 1,000 of the devices have been installed to date.

"The response was overwhelming," he said. "We've upped that now. We're going to be installing by springtime 140,000 thermostats. It's a matter of making sure we have the qualified installers."

Ballard also used the announcement to take a shot at Progressive Conservative leader Patrick Brown's plan to scrap cap and trade if the Tories win the election next spring and replace it with a carbon tax system.

"All of it would be lost if the province were to adopt a Brown carbon tax," he said. "Their program doesn't invest in Ontario."

PC finance critic Vic Fedeli said the minister's claim isn't correct, adding that the Tory plan would maintain all existing Liberal spending, including the program announced Wednesday.

"In our plan, we have $1.5 billion kept to make sure that all of the programs that are announced are kept in place," he said. "It's obvious that the minister is playing politics instead of actually looking at our platform before he critiques it."

The government said buildings generate nearly a quarter of the province's greenhouse gas emissions.

Ontario has pledged to cut greenhouse gas pollution to 15 per cent below 1990 levels by 2020, 37 per cent by 2030 and 80 per cent by 2050