Sunny Side Up

General Motors liked the idea of using the sun to power its buildings. But until recently, one immutable economic fact held G.M. back: The upfront costs were simply too high to justify the ultimate payoff.

G.M. is not alone. Even solar energy

But now, G.M. and a small but growing number of other companies and municipalities are getting solar energy from systems installed by others. Even though the installations are right on their own roofs, they buy the electricity much as they would from a utility