The change is part of a package of measures which the energy regulator says will help lower bills for many households.
But even if you are not on a pre-paid meter, are you still getting the best deal?
Read our guide to find out how you can switch.
Finding the cheapest energy deal depends very much on your area and your usage. There is no one cheap supplier.
When a supplier claims to be the cheapest company or to offer the cheapest tariff, it is usually based on a single user profile, which is not likely to be you.
Gas and electric suppliers frequently change their prices so it's worth regularly comparing what's on offer.
Switching does not involve any interruption to your gas or electricity supply, and there is no need to dig up the road. It is just a change to the company that supplies your gas or electricity.
You don't need to worry about power outages since the energy will be delivered through the same pipes and cables.
How does it work?
Ofgem recommends first asking your current supplier if there is a cheaper tariff you could be on, and whether you are eligible for fuel aid.
See how to find out who your supplier is below
You can also use switching websites to compare deals in your area.
You simply enter your postcode and some information about your gas and electricity usage. It helps to have a recent bill to hand.
Free switching services will simply contact your old and new supplier on your behalf, and agree a switching date.
You will then receive the paperwork from your new supplier in the post. Your existing supplier will continue to provide your energy until the day of the switch.
Switching used to take up to eight weeks, but energy companies said last year they were committed to slashing switch times to around two-and-a-half weeks by the end of 2014.
Then if you change your mind, you have 14 working days (from the date you signed the contract with your new supplier) to cancel without incurring any charge.
Who supplies my gas and electricity?
If you have just moved into a new property, the easiest way to identify your supplier is to ask the agent, landlord or previous tenant.
The previous tenant may have informed the supplier that the property is changing hands, in which case you should get a letter addressed to "The Occupier".
Often the supplier will put you on the most expensive "Standard Plan" so it is a good idea to shop around.
If you have lived in your home for a long time, you may not know who your supplier is.
For gas, you can call the Meter Number Helpline on 0870 608 1524
To find out the name of your electricity and gas plan:
Contact your electricity and gas suppliers directly and ask them.
Wait for your first bill to arrive from your electricity and gas supplier.
The plan you're on should be named on the bill itself and include details of unit prices
What if your new supplier raises its prices?
There is no limit on how many times you can switch. But one solution may be to consider a fixed-price deal.
These have slightly higher premiums, so may not appear among the cheapest deals, but they will lock the price for up to three years.
What is collective switching?
Collective switching is when consumers group together to negotiate a deal with gas and electricity suppliers.
Normally a third party will negotiate a better tariff on behalf of the group.
The idea is that they have greater power in numbers to negotiate good deals.
There are a number of questions you should ask of the provider before signing up.