Many people are very confused by the conflicting claims of different companies selling gas and electricity and end up paying more than they need to. There is however plenty of good, clear information about what each company charges and which one offers the best deal for your own particular circumstances. The first stop is energywatch, the independent gas and electricity consumer council - their website gives you comparison tables for each postcode as well as information on the level of complaint received about each company: energywatch

You can also buy electricity generated from renewable sources (wind, solar, hydro, biomass), which in most cases is slightly more expensive but with electricity prices generally very low a growing number of people prefer to pay this small amount extra to support the generation of clean power. Friends of the Earth have a very good analysis of how 'green' each of these suppliers is - while you can also compare prices at http://www.greenprices.com/uk/pricesbox.asp