Green energy firm Ecotricity claims it spends a higher percentage of its revenue on green energy initiatives than any other firm in the UK.
For the past five years Ecotricity has topped WhichGreen's website which compares the green credentials of every energy supplier in the country.
Ecotricity spent an average of £401.49 per customer on constructing renewable sources of electricity.
The second highest spender was ScottishPower, according to WhichGreen, which spent £102 per customer, followed by Centrica, which spent £38.
Meanwhile, EDF was responsible for spending £16.31 per customer on renewable, while npower spent just £4.38.
"In my opinion its a statistic that gets to the heart of the issues, cuts through the greenwash and spin of the Big Six and the small independents - it's the measure to me, of whether your deeds match your words," said Ecotricity founder and chief executive officer Dale Vince.
Ecotricity claims it invested £25 million in wind energy during 2007.
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