Consumers have been warned to brace themselves for the possibility of further energy price hikes and urged to take action to keep their bills down as a "matter of urgency".
SSE, formerly known as Scottish & Southern Energy, has already announced that from Monday next week it will increase tariffs by 9% on average in a move impacting around five million electricity customers and 3.4 million gas account holders.
Concerns have been raised that other energy giants could follow suit as temperatures plummet, in a further blow to households squeezed by high living costs and low wage rises.
E.ON has said that while it will not raise prices in 2012, no decision has been taken about what will happen when January comes around.
Martin Lewis, founder of consumer help website MoneySavingExpert.com, said: "Energy companies are like sheep - where one leads, the rest will follow. It is likely but not guaranteed that price hikes are coming. People should be taking preventative action."
Mr Lewis said people on a standard tariff should be looking into a cheap fixed tariff, which could save them more than £200 a year. Some fixed-rate tariffs also guarantee no price hikes for two winters.
He said people should act as "a matter of urgency" as some of the cheapest fixed deals have already disappeared.
"That is what happens in a price hike environment," he said. "There is only a finite amount of fixed money."
A survey published by Consumer Focus last month estimated that around six million households are planning to cut back on their heating this winter. Nearly four out of 10 households (39%) are worried about affording their energy bills this winter, and 70% of those, or six million households across England, plan to reduce their heating, the survey found.
Citizens Advice warned that many households are so financially stretched that "every penny counts". It is running Big Energy Savings Week from October 22 to 27 to help people get a better deal on their fuel bills and help them to use less energy. The event is funded by the six largest energy companies.