When it comes to the electricity itself, there is no difference at all. A cheap electric supply is the same electricity, it's simply provided by a new supplier (unless you opt for green energy - more on that here). As suppliers buy and generate different sets of energy they also have different prices. What's more, you might be on a tariff that is simply more expensive, such as a standard tariff. If you decide to switch electricity don't equate a lower price with worse service.
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.
It’s worth noting that you can switch for free with no exit fee 42-49 days before the end of your contract. Under Ofgem’s standards of conduct, energy firms have to give you between 42 and 49 days’ notice of your tariff ending. You can use this time to decide whether to stick with them, or switch. If you decide to switch, you won’t be charged an exit fee.