A billing error has resulted in thousands of customers being overcharged by Nova Scotia Power.

The utility says the efficiency rate has been charged twice on 13,000 power bills. The company is now in the process of notifying customers affected by the error.

Alfie MacLeod, Progressive Conservative MLA for Sydney River-Mira-Louisbourg, says he has heard from about a dozen constituents upset over their bills.

“How many other times has this possibly happened? I mean, people don’t always scrutinize their bills closely,” says MacLeod.

Nova Scotia Power says the average efficiency rate is about $7 per month per customer.

“The efficiency charge, which is one of the components of the bill, got calculated twice,” says utility spokesperson Neera Ritcey. “We do regret the inconvenience this has caused the customers.”

Ritcey says the error is due to a computer glitch; the system traditionally calculates the efficiency charge increase, as well as the general rate increase, at the same time, which is usually Jan. 1.

“Because this year the efficiency charge did not increase, did not kick in until mid-February, the system had this glitch,” explains Ritcey.

Nova Scotia Energy Minister Andrew Younger says he was concerned to learn of the error.

“Obviously it’s a computer issue of some kind and it does beg the question of what other issues may exist with Nova Scotia Power’s billing system. I can tell you, I’ll be checking my own power bill when I get home,” says Younger.

“It doesn’t matter if it’s 50 cents or a dollar, if there’s an issue that resulted in overbilling, then that’s a concern to me.

Nova Scotia Power believes the issue is contained to 13,000 customers. Those affected will see an adjustment on their next bill, along with an explanation for the error.

The utility says it rarely experiences such glitches, and is investigating to ensure it was a one-time error.

With files from CTV Atlantic's Jacqueline Foster