This summer's particularly hot weather appears to be to blame for the unusually high energy bills some Manitoba Hydro customers received last month, the utility says.

One customer says she got a bill for $700 in July — even though she usually pays about $150 a month for hydro.

A phone call to Hydro confirmed it was an error and the bill was adjusted down to $170, based on her meter reading.

The utility started noticing mistakes in billing in mid-July and is now in the process of manually reviewing any bill that was over $400 last month, said Scott Powell, Manitoba Hydro's director of corporate communications.

The Crown corporation's billing system looks at a customer's usage history and the current temperature to estimate energy consumption, he said.

Most of the customers who experienced the billing glitch were new customers, so Hydro's algorithm would have put more weight on the high temperature, resulting in a some very high bills, Powell said.

"With temperatures being quite a bit higher this year than what we've seen in the last 30 years, it's actually outside the range of what our system would normally accommodate," he said.

"So it puts more weight on that, and automatically drives up the estimates."

If you think you were affected by a billing mistake, you can contact Manitoba Hydro in Winnipeg at 204-480-5900. If you live outside the city, call their toll-free line at 1-888-624-9376.