Between January and March, a record 10,638 people complained to the Ombudsman Service about the Big Six gas and electricity firms, three times the number making their feelings felt in the same period last year.
Billing problems, unexpected charges and poor customer service topped the list of their gripes.
Richard Lloyd, executive director of consumers' organisation Which?, said: "The fact that consumer complaints continue to rise is further proof that the energy market is broken."
The major suppliers themselves received a staggering 5.5 million complaints last year. npower had the most at 1.3 million, followed by EDF Energy and British Gas, with 1.2 million each, E.ON (over 900,000), SSE (almost 500,000) and ScottishPower (300,000).
The average combined domestic gas and electricity bill has more than doubled since 2005, from £600 to over £1,200, and an increasing number of people are struggling to afford the power they need.
The Debt Advisory Centre Scotland says more than 660,000 Scots used credit to pay their gas and electricity bills in February, three times the number relying on cards or loans to pay six months ago.
Last month, regulator Ofgem announced it was referring the entire sector to the Competition and Markets Authority for an inquiry into its profit levels.
Last week, Ofgem fined British Gas £5.6 million for blocking business customers from switching to other suppliers. It also published new rules that are designed to make switching faster, easier and more reliable for all energy customers by August.
And there is no sign of an end to the bad news for the Big Six. According to a survey by independent electricity supplier Green Energy UK, only 50% of consumers trust the largest firms, and more than 90% want a provider that offers good customer service as well as competitive pricing.
Many consumers have come to believe that means looking to smaller suppliers. Switching service uSwitch.com says 72% would now move outside the Big Six, up from 56% last year and 52% in 2012.
The day uSwitch.com revealed these findings, small supplier Ovo Energy announced it was bringing the cost of its Cheaper Energy Fixed tariff down to an average of £998 a year, the lowest price on the market.
Days later, First Utility responded with its iSave Fixed July 2015 (v20) costing £4 less, at an average of just £994 a year.
Tom Lyon, uSwitch.com's energy expert, said: "Spring has sprung for consumers following a winter of discontent. The dominance of the Big Six has been well and truly challenged by First Utility, as it becomes the second small supplier in a week to offer consumers a better deal.
"This can only be welcome news. As competition heats up in the battle for hearts and minds, suppliers will have no choice but to offer superior service, lower prices and better value for customers."
He added: "This could well be the start of a price war among suppliers, and it is excellent to see some of the smallest leading the charge."
With several fixed-price tariffs coming to an end in the next few weeks, it could be a good time for many people to consider changing suppliers. Clare Francis, editor-in-chief at comparison site Moneysupermarket.com, said: "Customers need to take power into their own hands to seek out the best deal.
"One of the most popular products due to finish at the end of the month is EDF's Blue+ Price Promise April 2014.
"Customers will see their bills rocket by an average of £210 a year if they do nothing."
If you are thinking of making a move, check the cost of your existing tariff and your consumption from the past 12 months' bills, so you can make accurate comparisons. If you don't have them, contact your supplier for the information.
No one company or deal is best for everyone, the right one for you will depend on your energy use and where you live, as not all firms supply all areas.
If you have gas and electricity from separate providers, you are likely to save by opting for a "dual fuel" deal with a single one, while the cheapest payment option is generally monthly direct debit.
If customer service is important you, it is worth checking the service ratings given by Which? members before committing to a new provider.
The consumers' organisation asked more than 8,500 people to rate their current supplier.
Good Energy and Ecotricity came out equal top with five stars for customer service, value, billing accuracy and clarity, and complaint handling. They both received an overall satisfaction score of 82%.
Utility Warehouse, which scored 75%, Ebico (74%) and Ovo (73%) were next. First Utility scored 58%.
Further down the table, EON did best of the Big Six, at equal 11th with Sainsbury's Energy, on 45%. EDF (44%), ScottishPower, SSE (both 41%) and British Gas (39%) were next, with npower in 17th and last place on just 31%.
The simplest way to compare options and make the move is through a service such as Which.co.uk/switch, Moneysupermarket.com, uSwitch.com or Confused.com