It will make a donation of £25 when the customer goes on electricity-only supply and a donation of £25 will be made when the customer goes on a gas-only supply, plus a further £25 per fuel for every 12 continuous months across which customers maintain their electricity or gas supply with the company.
New customers will also receive a £10 discount on a Discovery Pass, the membership scheme which allows free car parking and a range of other benefits at local forests managed by Forest Enterprise England.
Forest Enterprise England chief executive Simon Hodgson said:
"Alongside the income we generate from suppling sustainably grown timber, we look for new business partnerships that offer additional sources of revenue to invest in the nation’s forests we manage.
"The extra funding helps us make them more interesting and exciting places to visit and we can continue with our conservation work."
Ecotricity was billed as the world’s first green energy company when it was founded in 1995, and now supplies almost 200,000 UK customers.