Starting July 19, anyone who buys Energy Star light bulbs and appliances won't be charged provincial sales tax at the till.
The deal, announced Wednesday by Premier Dalton McGuinty, will last for one year.
But the opposition said this is just a flip-flop designed to get the Liberals re-elected Oct. 10.
Conservative Tim Hudak said the Liberals cancelled a similar tax credit program in 2004 that also refunded the PST to customers who bought Energy Star products.
He said the Liberals have resurrected the tax break just in time for the fall election.
"This is conversion on the road to electoral defeat," Hudak said. But McGuinty said the Liberal refund is different and more convenient because people don't have to wade through applications they are exempted from paying PST right at the cash register.
"We've brought back a plan today which is a much stronger incentive," McGuinty said, adding the previous Conservative tax credit only had a "modest impact."
"We've gone beyond that."
The announcement is part of the Liberals' climate-change plan being rolled out as the summer election campaign gets underway.