I recommend (Money Saving Expert's Cheap Energy Club)[www.moneysavingexpert.com/cheapenergyclub].

It allows you to enter your existing provider, plan and usage data and then searches for cheaper deals. You can also sort for things you require (eg: monthly payments, renewable energy only).

Once switched, you enter the new provider details on your profile, then if a new deal arises that saves you a defined amount they will notify you (eg: if a new provider deal saves you an estimated £100 a year) so you can switch again. That way you don't even need to keep on top if it.

I just moved into a new student house, the previous tenants were with NPower. I entered their previous yearly usage based on the bills they left us. We switched and are estimated to save £900 a year, and our new provider is also renewable too! (We switched to Outfox the Market).