Minnesota utilities are banding together to warn their customers: Scammers are on the loose.

Utilities get thousands of reports of attempted fraud each year, as sophisticated scam artists posing as utility employees try to quickly wrestle a few hundred dollars from customers, usually on the phone. As winter sets in, and more people turn on their heat, reported scams increase about 30 percent.

"There are prevalent scams still plaguing our customers," said Becca Virden, spokeswoman for CenterPoint Energy.

The scams are easy to spot for those who know how they work.

Usually a caller will tell customers — often small-business owners — that their bills are overdue and power will be shut off if they don't quickly pay a fee. Often the caller demands that the customers drive to a store and buy a prepaid debit card to make the payment. Usually there is a strict deadline, often less than an hour to pay.

Business owners see losing their power as an existential threat, and they can panic.

"This is very much a science," said Lisa Jemtrud, of the Better Business Bureau of Minnesota and North Dakota. "What works is urgency, that they have to act fast, and also scare tactics."

But utilities say they give customers several business days to settle an overdue bill when they call, and they don't ask for customers to pay several hundred dollars using a prepaid debit card.

"We will never ask or require that you purchase a prepaid debit card," said Collin Kremeier of Otter Tail Power Company.

Another typical scam is a phone call, perhaps automated, offering a rebate if a customer makes a down payment or provides some critical personal information. All of these are red flags

Gas and electric companies across the U.S. and Canada believe the problem is big enough that they have designated Wednesday as "Utilities United Against Scams Day." In Minneapolis, representatives from Xcel Energy, CenterPoint, Otter Tail, Dakota Electric and Connexus Energy gathered on Tuesday at CenterPoint's Nicollet Mall offices to try to get the word out.

The scammers can come from anywhere, even overseas, they said. They can disguise their phone number. Some even can get Xcel or CenterPoint to come up on the victim's caller ID, or use the legitimate company's hold music and typical automated introduction to deceive customers who call them back.

They work in waves that hit parts of states all in the same few days, or even similar types of businesses, and they often have authoritative answers to customers' questions.

If someone calls on behalf of Xcel and the customer says their utility is Dakota Electric, the scammer might say Xcel has an arrangement with Dakota to collect overdue payments.

Police generally can't track down the scammers, so customers must protect themselves, the utility companies said. If customers feel threatened or are told they must pay within the hour, they should hang up and call the phone number on their utility bill to check things out.

The utilities say they have a message for the scammers, however.

"We're aware," said Virden. "We're helping our customers, and we're going to stop this."

Adam Belz • 612-673-4405

Twitter: @adambelz