Ontario's fiscal watchdog says the province will spend an estimated $15.2 billion to subsidize hydro rates for industrial and large commercial businesses by 2040.
The Financial Accountability Office says the spending will be part of a program announced in November that aims to cut rates that are higher due to green energy contracts.
The FAO says the program from the Progressive Conservative government will reduce hydro bills for an estimated 1,400 large business customers by a 14 per cent.
The watchdog says the province has more than 33,000 green energy deals and the amount paid to generators under the contracts are significantly higher than the average price of electricity in Ontario.
The FAO estimates that the program will cost the province $2.8 billion over the first three years.
It says the subsidy will gradually decrease as contracts expire over time.