Since 1996, when the energy market was opened up to competition, UK consumers have been able to switch energy suppliers to find a cheaper gas and electricity deal. Previously, Ofgem did set a maximum price for energy; but now Ofgem only regulates the market as a whole — that means creating a regulating schemes to support vulnerable households and more.
Retailers Include: AEP Energy , APG&E Energy Solutions , Calpine Energy Solutions , Constellations NewEnergy, INC , Crius Energy , Direct Energy Services LLC , Dynegy , ENGIE Resources , Entrust Energy , IGS Energy , Just Energy , Liberty Power , Next Era Energy Services , Nordic Energy Services, LLC , NRG Energy INC , Source Energy , Spark Energy , Starion Energy , Stream Energy , Talen Energy , TransCanada Power Marketing LTD. 
To be clear, no matter fuel portfolio of the plan you choose, your electricity’s make-up will be identical to your neighbors’. Depending on where you live, that could a mix of renewable and fossil fuels. Certificates offset your electricity use by putting an equal amount of clean energy into the electricity grid. If a plan is 100% renewable, that means it’s 100% offset with certificates.
uSwitch is a free service that handles the switching process for you. Once you've completed your energy switch, your new energy supplier will contact your old supplier and agree a switching date. You will then receive a welcome pack and letter from your new gas & electricity supplier. This will outline what you've agreed to, and tell you what happens next. There won't be any interruption in your gas and electricity supply.
Switching electricity supplier could shave pounds off your bills. But it’s not always about how much hard cash you could save. You might be fed up with poor customer service, you might want greater visibility of your usage through an app or you might want to choose your supplier based on their green credentials, or whether they supply a smart meter.