EnergyCheck is only an email update. It does not do the switching for you. They send you a monthly email letting you know whether you are on the cheapest tariff or not. If they have found a cheaper tariff they will tell you, but you will have to manually do the switch yourself. This would involve finding meter readings and all the hassle that is involved with switching via a comparison website. It will also only tell you whether there is a cheaper deal that pays them a commission, therefore it does not look at the whole of the market and you will likely be paying more than you need to. Their claim that you will never overpay on your energy again is therefore incorrect.
80% of the time, the cheapest deal was not shown. Hidden within the website the best deal was available, but as shown through Flipper's research, 97% of people can't find it.
45% of the time, the cheapest deal was not shown. Since free auto-switchers make money through commissions from suppliers they do not offer the best deal to their customers.