Nova Scotia Power overestimated its fuel costs this year and will rebate customers about $22 million, but homeowners will not see a decrease in their power bills next month, the company said Wednesday.

Those fuel savings will be offset by a new charge to fund a $23-million energy efficiency agency.

The utility had applied to the Nova Scotia Utility and Review Board for a reduction in residential power bills by 1.4 per cent on Jan. 1, citing lower natural gas and oil costs in 2009. This is the first year the fuel adjustment mechanism has been in effect.

"That's why we're getting the money back and next year we may not be getting the money back, or the year after that," said John Merrick, a consumer advocate.

"The fuel costs that Nova Scotia Power incurred in 2009 turned out to be lower than they had anticipated when rates were set for the beginning of 2009."

That means the average customer would get a rebate of between $1 and $3 a month. But the money will go toward funding the Efficiency Nova Scotia conservation programs for the year.

Merrick said while it's too bad the rebate is offset, he said the new fuel rule is an improvement that forces Nova Scotia Power to be more accountable.

"NS Power is committed to make filings monthly … of information relevant to the prices they're paying for fuel and allows all interested parties the whole year to monitor what is happening," he said. "I'm quite confident that the process is working to the benefit of ratepayers."