Like many consumers, David Polstein had already done much to reduce energy use in his large Victorian home in Newton, Mass. He replaced his appliances with energy-efficient models, installed better heating and put in new insulation. But he was unable to get a solar system to reduce his utility bill, he said, because his roof is too small and shady to make it worthwhile.

Now, that could be changing. Mr. Polstein is considering joining a so-called community solar garden that is under development in his part of the state, one of many similar new arrangements now available in Massachusetts. Through the approach — largely pioneered in Colorado and spreading across the country — customers buy into a solar array constructed elsewhere and receive credit on their electricity bills for the power their panels produce.

For developers, such shared or community solar arrays create a new market from the estimated 85 percent of residential customers who can neither own nor lease systems because their roofs are physically unsuitable for solar or because they do not control them — like renters and people living in large apartment buildings. And for those customers, it offers a way into the solar boom, whether they seek to contribute to the spread of clean energy or to reap the potential cost savings.

“I pretty much realize that if I’m going to do this sort of thing,” Mr. Polstein, a violin maker, said, “this is the only way I’m going to be able to do it.”