If you only do one green electricity thing, do this. Switching to a green electricity provider makes more difference than all the other Plug Out actions combined. It will save about a third of your household CO2 in one go.
Here's how it works. The same amount of electricity you use gets produced somewhere in the country from natural sources like the sun or wind or waves and pumped into the National Grid. Then you just use it the same as you do now. Simple really.
More info from the Green Thing Wiki >>
Here's a thing ... Sweden plans to become the first country to run completely on renewable energy and will stop using oil completely by 2020. Meanwhile, by the time the UK finishes building its next nuclear reactor, Germany will be generating more electricity from solar power than all our nuclear power stations produce today.