Religious leaders are being urged to see the light by putting solar panels on temples and church roofs.
If all temples, synagogues, churches and mosques switched they could earn £29million, British Gas said.
They would make money by selling the electricity to the grid with feed-in tariffs, while saving emissions equivalent to 500 US flights.
Britain’s 16,247 churches could make £17.3 million from selling on electricity.
Mosques would make £6.3million, Hindu temples £2.3million, Jewish synagogues £1.4million, Sikh temples £1.4million and Buddhist temples £888,000. Collectively they could also save £5million in energy bills. In Birmingham, the Masjid-e-Hamza Mosque will be the first to benefit from feed-in tariffs and expects to earn £6,400 a year.