She criticised the energy company for the thoughtless gaffe at a time when bills are going up and major price rises are due to be announced soon.
Barbara said: "I’ve had a problem with my smart meter and thought it might be a part for it. When I opened it, it was the socks.
“They’re a joke. Considering the time we are in with heating going up I thought it was a bit of a cheek.
"I’m dreading it when they readjust my standing order.”
E.ON reportedly sent a free pair of the socks to 30,000 customers who had engaged with one of its energy saving campaigns last year.
The gifts were to encourage them to continue to save energy although company has since apologised.
Barbara, who works at a jewellery shop in Hartlepool, and is a coordinator of the Hartlepool WASPI pension campaign group, said her bills have gone up by about £10 a month.
She added: “Apparently it was part of another promotion and there is an apology but it still doesn’t help.
"I know it’s a global thing with prices going up but it’s money that is just being wasted.
“It’s our money that we’re paying our fuel with and they spend it on socks.”
Apologising to customers E.ON said: “If you recently received a pair of socks from us, we would like to say we are incredibly sorry for how we have made some people feel.
“In light of the seriousness of current challenges that many people are facing, this mailing should have been stopped and we are sorry.”
Another energy firm Ovo also apologised to customers recently after sending an email containing advice on how to keep warm including putting on a jumper, eating lentils or ginger and cuddling up to pets.
Experts expect that the price of energy will soar by more than 50% to around £2,000 for the average household when regulator Ofgem announces its new price cap next month.