According to the regulator, Ofgem, it is possible to save about £300 a year if you switch your gas and electricity provider.
The best savings involve taking out a "dual fuel" deal, where one provider supplies both forms of energy.
Many people have been put off switching, but Ofgem maintains the process is very simple.
Am I allowed to switch?
Not everybody is able to switch their supplier. If you are in debt to a supplier, you might not be able to.
If you have a pre-payment meter and you owe more than £500 for gas or electricity, you might not be able to switch.
Fixed deal or Standard Variable Rate?
There are two main types of energy deal, a fixed-term contract, typically lasting a year or 18 months, and a standard variable tariff.
If you are one of the two-thirds of householders on a standard variable tariff, the potential for savings is larger.
However, over the past few years the gap between standard variable tariffs and fixed rates has narrowed, as can be seen from the graph below.
What information do I need to switch?
You will need:
- your postcode
- the name of your existing supplier
- the name of your existing energy deal
- an idea of how much gas or electricity you use, which should be shown on your bill
How long will the switch take?
The change should take no longer than 17 days. That includes a 14 day cooling-off period. Your supply will not be interrupted during that time.
If you are on a fixed-rate deal and decide to switch before it ends, you may be charged an exit fee. But if you are within 49 days of the end of the deal, you should not be charged.
What comparison sites should I use?
You can contact your supplier directly, and ask if they can give you a better deal. But there will be a wider choice of deals through price comparison websites.
Ofgem provides this list of approved sites: Quotezone, The Energy Shop, Runpath, Simply Switch, My Utility Genius, Switch Gas and Electric, Energylinx, Unravel It, Money Supermarket, Energy Helpline and Uswitch.
These sites do not always point consumers in the direction of the cheapest deals. They tend to promote those that you can switch to straight away, and with whom the websites have made an agreement.
"To get the best deal when switching energy supplier, it's important that you make sure the site you are using shows the whole of the market and not just suppliers or deals that they earn a commission from," said Mike Rowe, from Simply Switch.
Better deals may be available if you are prepared to wait. However any site approved by Ofgem has to include a clickable option to see all tariffs available, not just preferred suppliers.
Such sites have a "whole of market" button, allowing you to see all the deals on offer.
Citizens Advice: Help for switching supplier
Ofgem: How to switch supplier
Which? Compare and switch supplier