TORONTO - Ontario's energy minister says he expects Enbridge will be reasonable with people who owe hundreds of dollars because of a mistake made by the company.

"My hope is that Enbridge will be sensitive to their customers -- that's my expectation," Brad Duguid told reporters on Wednesday.

About 100,000 customers are learning they owe hefty sums to the gas distribution company due to a glitch that led to accounts being under-billed earlier in the year.

"So far the indication from Enbridge is that they will be, but we'll certainly be watching this closely to ensure that that in fact is the case," Duguid said.

He acknowledged the unexpected bills will be a financial problem for some.

Customers in Enbridge's budget billing plan pay instalments based on their gas consumption for the previous year. But the company admitted it made a mistake and set some payments too low.

Enbridge said the miscalculation means some customers will be receiving notices this month telling them they need to pay anywhere from $400 to $1,300, or more.

Affected customers are being told they can spread this readjustment payment out over the next year if they need to, with no penalty.

Enbridge gas distribution is part of the larger Enbridge company but is not directly associated with the current oil pipeline spill in Michigan.

Duguid said the gas company's rates are regulated by the Ontario Energy Board but this seems to be a glitch that occurred in the company's computer system.

He pointed out the extra money some will pay is not due to an increase in energy costs.

"This Enbridge glitch isn't an increase in fees, it's just an allocation of when they pay their fees for the year," Duguid said.

"They didn't collect enough over time on a monthly basis for some of their consumers."