Believe you may be among the 3.5 million households or 300,000 businesses owed part of £400m from the Big Six? Here's how to claim it back.
With questions looming over high prices and why it took so long to restore power over Christmas, there will be no respite for the 'Big Six'.
The coalition has unveiled measures it says will knock £50 off the average energy bill, but some of that cost will be absorbed by taxpayers.
Energy regulator Ofgem hopes changes, including banning suppliers from offering complex tariffs, will help simplify the market for the consumer.
Here are some of the key points:
Simpler tariffs - from 1 January
- Suppliers will be limited to offering up to four "core" tariffs per fuel (electricity and gas) and per meter type
- Complex multi-tier tariffs are banned and suppliers must structure their tariffs using only a single unit rate
Clearer information - to be introduced from April 2014
- New rules will be in place requiring suppliers' routine communications to consumers to be clear, easy to understand and personalised to them
- Suppliers will be required to give all their customers personalised information on the cheapest tariff they offer for them
- Suppliers will use a new Tariff Comparison Rate, in bills and a range of other communications, to help customers compare tariffs at a glance
- Ofgem is also requiring suppliers to provide personalised cost projections for the following 12 months based on the customer's actual, historic consumption
Ofgem has said its latest reforms are aiming to "restore consumer confidence" in the energy market.
The energy regulator unveiled reforms including banning suppliers from offering complex tariffs to create a "simpler and clearer" market.
Andrew Wright, Ofgem Chief Executive, said: "It is getting easier for consumers to get a better energy deal and by April further help will arrive in the form of much clearer and personalised information.
"The aim of our simpler, clearer, fairer reforms is to ensure competition bears down hard on prices. Profits are not an entitlement, they should be earned by companies competing keenly to offer consumers the lowest prices and the best service.
"Now it is up to suppliers to build on our reforms to restore consumer confidence in the energy market. There are good signs that they are taking up this challenge.
The company said they would "not hesitate to take further action" if it sees "evidence of further barriers to competition", adding that they would produce an annual report to consumers on the health of the energy market.
Energy regulator Ofgem has unveiled reforms designed to create a "simpler, clearer and fairer energy market".
The organisation say they are banning suppliers from offering complex tariffs and will take steps to simplify the charging system.
Reforms include limiting suppliers to just four tariffs per customer for both electricity and gas.
Further changes, due to be enforced from April, include making suppliers tell customers regularly which of their tariffs are the cheapest.
The body claim the reforms are the biggest changes to the retail energy market since competition was introduced in the late 1990s.
The Co-operative Energy firm has announced a price rise of 2.5% on average.
In an email to customers, the company said: "As winter sets in and some energy companies raise their prices by as much as 10%, we’ve got some good news for you to warm to.
"Co-operative Energy is raising its prices on 8 January…but only by 2.5% on average across all our customers."
Energy Secretary Edward Davey called E.ON's price rises announcement "disappointing news".
Bur Mr Davey stressed:
This rise is ... lower than it would have been as a result of Government action to reduce the impact of price rises on consumers.
As part of their announcement today, E.ON have confirmed they will pass on these savings to their customers.
This does not let energy companies off the hook.
Asked about the timing of E.ON's price rises announcement, which came amid media focus on the death of Nelson Mandela and the devastating storms across the UK, Downing Street said, "It is for them to explain their decisions."
E.ON has announced its customers' dual fuel energy bills will increase by an average of 3.7% from January 18.
The company said that means the average variable dual fuel bill will go up by £48, electricity only prices will increase by 3.7% or £20, and gas only bills will climb by 4.6% or £37.
Chief executive Tony Cocker said changes announced by the Government earlier this week reduced the overall level of the rise that was necessary to cover extra costs.
The energy firm said it was "working hard to limit the impact on its customers" by announcing a lower average percentage rise than any other major supplier.
Earlier this week, E.ON said it did not expect to have to raise prices in the next 18 months "as a result of social or environment obligations".
But E.ON also warned, "There remains a risk, however, that increases in network charges or wholesale energy costs for example could force a price increase".
The announcement followed the Government's shake-up of green levies on Monday.
Energy supplier E.ON will increase prices by an average of 3.7% from January 18.
Prime Minister David Cameron has told ITV News' Deputy Political Editor Chris Ship that the coalition's announced cut in energy bills was not in response to Labour's proposed energy price freeze.
Speaking in China, Mr Cameron said: "We have been discussing within the coalition the issue of energy bills for years now. It has taken me longer than I would have liked but I'm very glad we put in place at least some relief on the issue of energy bills."