And God said: “Let there be light,” and there was light (Genesis). And the vicar saw the light, and dimmed it (Instructions from the ecclesiastical environmental management committee).

As Germany's Christian churches go green, Sunday service is becoming chillier and darker. Shocked by the revelation that church buildings are responsible for an annual 18 million tonnes of carbon emissions — about 3 per cent of the energy-related total in Germany — religious leaders are cracking down on prodigal parishes.

Churches that achieve a big reduction in their carbon footprint receive a special label of approval, the so-called Green Cockerel.

Vicars have already begun proudly displaying the symbol in the hope that it will attract environmentally sensitive worshippers.

“We're emitting from our churches about the same as the whole state of Slovenia,” Jobst Kraus, of the Bad Boll Academy, calculated.

Collections used to focus on roof restoration. Now, as German Christians take up the burden of saving the planet, the money is for solar panels.

Boilers are being replaced. Stern notes pinned next to light switches remind users that they have a Christian obligation to save the planet.

Old hymn books are not being replaced. Churchgoers are encouraged, if they can see through the gloom, to read the words from large screens by the altar. Choristers are being urged to wear their ruffs two or even three Sundays in a row and cut the laundry bill.

“Some parishioners are keeping their foot warmers in the church,” a Catholic priest in Cologne said. “Most keep their coats on.”

Poorly insulated churches with leaking roofs have been a problem for centuries. Although ancient churches typically have thick stone walls, the high vaulted ceilings, wooden doors and draughty nooks and crannies have made them a nightmare to heat.

Since the Evangelical Protestant and Roman Catholic Churches are leading property owners in Germany — not only places of worship, but also daycare centres, hospitals, residential and nursing homes — they have become serious environmental sinners.

“When you think how many, or rather how few, people actually come to church you can see how we are per-capita offenders,” admitted a minister involved in the greening of the Protestants. ”It's like fuelling a large plane across the Atlantic only for the sake of transporting a family of five.”

So the communion wine has to do the warming. “Room temperatures in winter of 18C [64F] are simply too high in a badly insulated church,” Christian Dahm, one of the Church's new energy advisers, said.

“Quite apart from anything else, you run the risk of valuable installations, the organ, say, or a carved altar, suffering because of the relative lack of moisture in the air.”

Father Klaus Breyer, a Green Cockerel organiser, said: “One of the good things about this environmental campaign is that it is creating a new parish culture. Everyone in the church community has an idea as to how we can save energy and can chip in.”

The theology is clear: Christians have a duty to protect God's creation. Other nations are starting to ride the green Christian wave. In the US there are No-Gasoline-Sundays when clergy and choristers bicycle to church. The parish newsletter is e-mailed rather than printed.

The Church of England is committed to cutting its carbon emissions by 40 per cent by 2050. By the year 2030 Church of England parsonages should all be using solar hot water.

The Germans are well ahead on the path to a cleaner Church. Parishes in northwest Germany report up to 60 per cent reductions in their heating bills over the past year and — thanks to exchanging 60-watt bulbs for 10-watt ones in parish halls.

The Evangelical Protestant parish of Cologne-Dünnwald reports a 52 per cent cut in water consumption. Parish officials were unable to say what effect this has had on services but it does seem that Germany may be inching towards water-free christenings.

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