But in practice, such bonds have been a challenge to pull off. Electric utilities have issued bonds backed by certain tariffs charged to customers, and in 2010 SunPower, a manufacturer of solar energy systems, issued bonds tied to an Italian solar farm.

The SolarCity deal is different, analysts said, and could show how much of a market exists for the asset class. Although rooftop installations have boomed in recent years, the contractual arrangements are relatively new and can vary from company to company and state to state. That means they often lack the performance history and standardized terms considered necessary for securitization, the process of bundling many loans into one investment.

“You’re looking at, from most of the proposals we’ve seen, 10-, 15-year bonds,” said Michael Dean, a managing director at Fitch Ratings. “Two years of history, three years of history doesn’t cut it for us.”

In addition, because the technology is evolving rapidly, there is the risk that more attractive systems will emerge over the life of a contract, or that utility rates will drop. Solar installers have used the fact that they can offer electricity to customers at a lower price than conventional utility rates as a big selling point. Without that, customers might seek to renegotiate their terms or abandon the systems.

Mr. Dean said utilities have had low default rates among customers because “they can turn your electricity off if you don’t pay.” But the solar companies “don’t have that same hammer,” he added, because the customers are still connected to the grid and can turn back to the utility for lost power if the solar company repossesses its equipment.

Other risks stem from the fact that the companies making, installing and maintaining the solar equipment are young and have tended to go out of business, raising questions about how to guarantee long-term performance.

SolarCity has addressed some of these risks by shortening the term for the bonds to 13 years, said Benjamin Shih, an analyst at Moody’s. “Once you start shortening the time horizon, then it’s less likely that the utility rates will change drastically,” he said, or that the equipment would become obsolete.