MANCHESTER, N.H. — After two years with low enrollment, New Hampshire’s largest electric utility is phasing out a program that allows customers to pay more to support renewable energy.

Utilities are required by law to offer customers the opportunity to support renewable energy by paying a higher rate – usually about 30 percent. But if not enough customers sign up, a utility can get permission from the state Public Utilities Commission to pull the plug. That’s what happened with Public Service Company of New Hampshire’s EarthSmart Green program, reports New Hampshire Public Radio.

The company says it would take just 1 percent of its total customers signing up to keep the program alive, but after two years, only 148 customers were enrolled, or about .04 percent.

Other utilities face similar situations. Unitil, which is weighing whether to continue its program, has just 25 people signed up, also about .04 percent of its customers.

“We gave out flyers, we give customers who do enroll some stickers (and) some clings they can put on their cards to try to generate some word of mouth, but it just seems to not really be growing much at all,” spokesman Alec O’Meara said.

Participation has been a bit higher at the New Hampshire Electric Cooperative, where customers can buy renewable electricity in “blocks” that cost $3 a month and represent about 100 kilowatts. At 1.2 percent participation, North American Power has been the most successful seller of green energy in New Hampshire.