Generally, the generation of electricity is unrelated to anything on your bill. Power plant companies generate electricity and sell it to utilities as well as retail electricity providers in deregulated areas. The electricity is then resold to you, the customer. Transmission and distribution is taken care of and charged to you by your utility, regardless of what company supplies the electricity. These charges are separate from the supply portion of your bill.
With moderate fluctuations taken into account, the variable plans is still cheaper. Our bill is approximately $10 more in the winter, but we’d still save $138 over the course of a year. It’s more a question of whether you can roll with the punches of an unpredictable rate, or would sleep easier knowing your bill is going to look the same month after month.
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.