Toronto Hydro is warning customers not to give out credit card information to telemarketers trying to sell energy-saving devices over the phone, saying the callers are falsely identifying themselves as part of the company.

Toronto Hydro vice-president Blair Peberdy told CTV Toronto he was surprised to receive one of the calls himself. The person on the phone said they were calling from head office, and tried to sell him a product he hadn't heard of before.

The callers say the product simply plugs into the wall and can drastically reduce one's hydro usage and bill. The person who spoke with Peberdy told him it came with a money-back guarantee. But no such product exists.

"He proceeded to pitch me on this device that Toronto Hydro is offering to customers… that would save on my bills by 40 per cent," he said.

Peberdy said he was told the device would "slow everything down" in his house, reducing energy consumption.

"That's ridiculous," he said.