More than half of annual household energy will be consumed in the next four months, costing consumers £2.2 billion more than it could do.
As average temperatures halve from 12°C in October to 6°C in January, energy usage will double, according to First Utility, an independent supplier.
This spike in energy consumption, along with its research which found a Big Six standard variable customer pays an average of £293 per year, means £2.2 billion more than necessary will be spent on gas and electricity.
Around 85% of UK homes are served by a Big Six supplier, with 70% of those on the Standard Variable Tariff.
There are a number of measures energy customers can take to reduce their usage. Some ways to do this are by switching to energy efficient light bulbs, blocking unused fireplaces and moving furniture away from radiators to allow the heat to spread.
For as little as £20 spent blocking the chimney consumers could save up to £153 a year.
Ed Kamm, Managing Director of First Utility, said: “Households who have never switched are likely to be overpaying to the sum of £300 annually on a Standard Variable Tariff. Our message is to switch now to get on a cheaper tariff before winter energy usage spikes and also look at ways of reducing energy waste in the home.”