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.
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.
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.