Taking questions about the decision today, McGuinty wouldn't even offer a ballpark estimate of the cost, saying it is "the subject of continuing conversation."
The Liberals quietly pledged this weekend to cancel construction of the 280-megawatt natural gas-powered facility in Mississauga, Ont.
The local community has opposed the project since it was announced six years ago, but McGuinty says a changing population and lower demand for power prompted his decision now.
McGuinty's political rivals are slamming the move just days before the Oct. 6 election as an attempt to save Liberal seats.
The government spiked a similar project in neighbouring Oakville almost a year ago, but McGuinty couldn't put a figure on that cost to taxpayers either.