Families will see energy bills rise by up to 30% as a host of affordable energy deals end, but the installation of 'smart' meters in the home could eventually bring costs down, a provider has said.
A handful of tariffs from EDF Energy, British Gas, E.ON and Scottish Power are due to expire during the next two weeks, according to website TheEnergyShop.com.
So what will happen?
Families who have signed up for one of eight tariffs in the past year-and-a-half will now end up on their suppliers' standard electricity and gas plans, meaning their bills could rise by up to £266 a year.
This is bad news for those parents who are already struggling to cover the cost of basics for themselves and their children.
However, under government plans, new 'smart' meters for for homes and businesses could help to cut energy use - if they are used correctly, British Gas said.
This is despite their huge installation costs being passed on to consumers, who will see a £6 rise in their fuel bill every year by the end of 2015.
Installing the technology, which will be in all homes by the end of 2019, is set to cost £11.5 billion, British Gas and Oxford Economics said.
Net savings of £14 billion are expected nationally, though, which means every household will be £65 better off each year.
But these savings are a long way off for those families who will be struggling to pay their bills when their tariff changes in two weeks' time, and many are going to be thinking about switching energy providers.
It is expected the steepest increase will be for those currently on Scottish Power's Direct October 2012 tariff, which runs out on September 30.
Families who use this tariff could see their bills increase to £1,170 a year from £904 a year - a £266 rise.
TheEnergyShop's Joe Malinowski said: "We are advising that people now go for a fixed-price energy deal as - with across the board price increases expected shortly - a variable deal exposes you to higher bills."
At the moment, the cheapest tariff is from Sainsbury's at £1,067 a year, but the cheapest fixed-price deal comes from OVO Energy, at £1,088 a year.