Major supplier of home energy including gas and electricity.
npower say You could save £349 off your energy bills if you switch to npower’s online tariff and pay by monthly Direct Debit. 
ScottishPower is the largest developer of on-shore windfarms in the UK. Voted No.1 by WWF for doing the most to tackle climate change.
Compare gas and electricity prices for home and business users. Also lets you compare home phone costs. 
Compare energy, landline and mobile phone & broadband. Also financial services such as insurance etc, but for insurance the specialist insurance sites may be better.
The Consumer Association's fuel comparison and switching service. Only does gas and electricity, not the other utilities.
Energywatch say about £1bn could be saved if all fuel users were on the most cost-effective tariff. The chances are that if you have not switched at all since the fuel market was freed up, then some of that saving is yours. Even if you have switched, it is worth checking periodically that you are still with the best supplier and on the best tariff for your kind of fuel use.
To save time comparing costs, you could go to one of the fuel price comparison sites listed in the column on the right. You need to enter your post code, the name of your current supplier and preferably the amount of fuel you use, either in £'s or in units. It only takes a few minutes to get them to check whether a different supplier could save you money. Those price comparison companies do a good job and usually give a reliable indication of the cost other companies would charge and the amount you could save.
If you want to check their estimate against the fuel supply company themselves, click on the supply company logo at the top of the column on the right. Enter the same information and it will only take a minute or so to check whether the comparison company calculation is confirmed. You will also be able to see whether there are any special deals on offer.
Whether you go with the price comparison company estimate or go direct to the fuel supply company, you can switch supplier there and then. You do not have to tell you present supplier or do anything else - your new supplier will do it all for you. The companies make some big claims about savings to be had, but if independent Energywatch themselves say there is £100,000,000 to be saved nationally, a chunk of that could be yours! The whole process only takes a few minutes and the potential savings are enormous.