As the Kyoto agreement on climate change finally becomes law, many of us are more conscious than ever of the need to do our bit to save the planet.

One option is to choose a power supplier that uses renewable energy sources.

Or is it?

Simon's discovered that in doing so you might make no difference at all to the amount of green energy produced.

That's rubbish

For most people wind power is probably the image most people have of renewable energy.

However, while it is the biggest source in Wales, across the UK it is the burning of rubbish that comes top.

The gases produced from rubbish tips is then burnt to generate electricity.

Formerly the gases would escape into the atmosphere - so this way they're used.

Most popular forms of renewable energy in the UK 1st - Landfill gas 2nd - Hydro 3rd - Wind 4th - Co-firing

Top of the renewable charts comes landfill gas - more than 40% of renewable production last year.

Then hydro-electric power, which is the top source in Scotland.

After that comes wind power, most of it on-shore, and the one which grabs the headlines.

Fourth, and little known, is co-firing.

This is coal burnt alongside other renewable fuels, hence reducing the volume of carbon dioxide emissions.

Expensive

Much of Britain's hydro-electric capacity was installed years ago and actually produces quite cheap electricty.

But on the whole renewable energy is expensive to produce - and expensive to buy.

Some of the newest developments are offshore windfarms which are very costly to set up and run.

The only reason that such developments are being built is that electricity companies are forced by the government to take an increasing proportion of their power from renewable sources (see box).

Renewable obligation - as % of suppliers' total 2002 - 3% 2005 - 5.5% 2010 - 10.4%

Although the major suppliers offer customers the chance to have their energy supplied from renewable sources, the fact is that they have to meet these targets regardless.

And because each person deciding to change is so negligible in the wider context - it really makes no difference to the supplier whether you switch or not.

However, people can make a difference by choosing smaller suppliers such as Ecotricity, which create all of their energy through renewable sources.

Other stories in today's programme

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Insurance companies have been told they'll have to continue paying compensation to workers whose lungs have been scarred by asbestos. The insurers had argued that because the condition has no physical symptoms, they shouldn't have to pay damages. Rob's been looking into it.