The thing while switching is to verify uswitch (or whatever comparison engine you are using) numbers against terms and conditions and do your own maths.
Majority of energy providers will use two types of "dirty" tricks to make their price more appealing - either a daily charge or higher charge for the first XXX kWh in a year. The more of us switch to low energy sources, LED lighting and better insulation the higher those "cover our basic costs" charges become year to year. But focusing on pure energy prices, nobody is really controlling those "standing" prices, let alone the terms and conditions of how these charges are applied. And sometimes, without verifying the automatic calculations of the comparison engine, you can unnowingly manouver yourself into constant higher costs. As an example:
Let's say you are coming from a tariff that has daily charge to a new, seemingly cheaper tarrif that charges higher rate per kWh up to 900 kWh a year for electricity and up to 2680 kWh a year for gas and their terms and conditions speculate it is calendar year, rather your membership year. From previous bills you know you use, let's say 15kWh per day of electricity and 20kWh per day of gas when you use central heating. Which means that you will pay that higher rate for 90 days of electricity and 134 days of gas usage in winter months. That means you will not see those cheaper rates for the rest of this year and minimum first quarter of next year. All in all, you switched over to cheaper plan, but ended up paying almost half a year in a row at much higher prices.
Until "standing charge" and "first XXX kWh" scam is dealt with by regulators and we are left with pure prices per unit, all that switching vs break out of your bill you see on your bills, is there to ef with you and introduce enough confusion to numbers to get you move in circles between handful of companies just massaging and repackaging numbers. For many of us, staying on older "freeze" tariffs from decade ago with old terms and conditions might have been much cheaper choice than switching to new ones, regardless of what uswitch numbers suggest.