Energy: How dirty is your power supplier?

Energy: How dirty is your power supplier?

Cheap it may be. But is your electricity supplier clean or downright dirty? The argument over coal-fired power - often rated as the filthiest - is now white hot. The row has raged through the Guardian's comment pages, which have seen green campaigner George Monbiot go head to head with former National Union of Mineworkers leader Arthur Scargill over E.ON's plan to build a new coal-fired power station at Kingsnorth, Kent.

Now Guardian Money can show those who care about carbon emissions the facts about their electricity supplier. And people are concerned.

When we revealed a fortnight ago how to find the cheapest gas and electricity suppliers, E.ON emerged as one of our best buys. Readers then told us that, instead of saving money with E.ON, they wanted to switch away from the firm to protest against its involvement with new coal capacity at Kingsnorth, site of the Camp for Climate Action this summer.

Electricity has to come from somewhere - and most generation involves CO2 emissions or nuclear waste.

Our graphic shows just how the mix varies from company to company - the figures from electricityinfo.org cover the year to March 31, 2007, except for Utilita where it is the previous year. The numbers throw up questions over just how clean some suppliers with green credentials are - only Good Energy is 100% sourced from renewables such as wind and waterpower. All companies have been set a government target of 9.1% of electricity from renewables.....continued below

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by next March, rising to 15.4% by 2016.

Top of the coal burners is Scottish Power, where 55% of its generation comes from coal, substantially greater than its rivals. Not surprisingly, it also heads the carbon emission table.

EDF is the next biggest coal user at 47% followed by npower at 44% and E.ON at 42%. E.ON's percentage is likely to rise should Kingsnorth get off the ground.

By contrast, British Gas (Centrica) takes just 18% of its needs from the fuel. It uses its own gas for electricity generation. But for those whose main worry is nuclear energy, Scottish Power's supplies to its five million customers comes out well at only 1%.

Ecotricity, which figures prominently on green lists, mixes coal, nuclear, renewables and gas in almost equal amounts. The firm concedes it does not have a 100% green fuel mix although it does offer a 100% green supply for those who want it. "We are working towards more renewables. Our most popular tariff is made up of around 70% brown energy. Buying existing green energy, which is what most 100% tariffs contain, does nothing at all to reduce CO2 emissions or increase UK green energy capacity - you simply take something that already exists and have it for yourself.

"Robbing Peter to supply Paul is how we like to describe it. Most 100% green tariffs are a con, because they tell you you'll reduce your carbon footprint etc, but don't tell you someone else's will go up as a direct result. Nothing really changes - it's just a redistribution of existing green sources."

Scottish Power says its high coal dependency is due to inheriting coal-fired stations - it owns Longannet station in Fife, one of the biggest in the UK. It is investigating "carbon capture" techniques. These cut down on emissions but are controversial on cost and energy grounds.