The study revealed that 19 per cent of households had received an incorrect bill from their energy supplier, although this is down from 25 per cent on last year.
A total of 11 per cent of respondents said they had been wrongly billed by their energy supplier more than once over the last two years.
The number of households owing their supplier money due to a discrepancy between the estimated bill and a real bill increased from 9.6 million (37 per cent) last year, to more than 10 million (39 per cent) this year.
The average amount owed is £146, although 14 per cent owed between £200 and £400, while 7 per cent owed more than £400.
More consumers provided their own meter readings to their supplier rather than relying on estimates, with 80 per cent of households having provided a meter reading n the last six month, up three per cent on last year and 16 per cent on 2009.
Ann Robinson, director of consumer policy at Uswitch.com, said: “There is a toxic link between estimated bills, inaccuracy and debt, which has to be broken.
“Estimated bills should come with a health warning and with a very simple message and advice about them.
“If a bill is estimated then the customer should be encouraged to get in touch with a correct reading so that an updated and accurate bill can be sent.”
Trade association Energy UK said the drop in inaccurate bills is “a clear sign that things are improving”, and that smart meters will help reduce the number of inaccurate bills further.
In a statement, Energy UK added: “For now, customers can help by making sure suppliers have regular meter readings.
“There are also industry reforms underway. New reforms are putting the focus on customer service and information and making the energy industry easier for customers to understand.”