Last year, Prestonwood Baptist Church, a conservative megachurch in Plano, Texas, enlisted the help of Energy Education, Inc. to help with its efficiency problem. Prestonwood, which caters to a Sunday crowd of 26,000, has four separate buildings and a million square feet of usable space. Its monthly utility bill was $250,000. “The Bible says, ‘Let nothing be wasted’,” explains Mike Buster, Prestonwood’s executive pastor. “The Bible commands us to be good stewards of all of our resources. To be able to save money and use it for ministry and missions—I was very concerned with that.” Seven months into the program—which consists of training staff to turn off lights and computers and rearranging program schedules to maximize efficient use of buildings—the church has saved nearly half a million dollars.

In San Francisco, an outfit called Interfaith Power & Light, started by an Episcopal priest named Sally Bingham, has 4,000 churches, synagogues, mosques and even a group of Jains (people who follow an ancient Indian religion) on its roster. Its state chapters teach congregations how to conserve energy, skills it hopes they’ll also apply at home. The Quakers who, not surprisingly, have been at the forefront of the green-church movement, are seeing a surge of interest in the intersection between faith and ecology. Ruah Swennerfelt runs Quaker Earthcare Witness, a nonprofit in Vermont. In November, she and her husband, both in their 60s, will walk the 1,400 miles between Vancouver and San Diego—“it’s a pilgrimage of sorts,” she says—and she has been cold-calling the Quaker communities along the route, asking if they wouldn’t mind being hosts. Of 46 “meetings,” 40 have said yes. Swennerfelt practices what she preaches. She works out of her home, which is off the grid: in her case, the lights are off, even when somebody is at home.