“Initially there was some euphoria and some market overreaction to the idea,” said Aneesh Prabhu, a credit analyst at Standard & Poor’s. “But the bloom has come off the rose.”

The idea behind yieldcos was simple on its face: Bundle together completed or nearly completed power projects that ostensibly offered steady, low-risk cash flows in the form of power purchase agreements covering electricity payments over 15 years or so. Because they were tied to power plant developers — including Abengoa, NextEra Energy and Pattern Development — the yieldcos would have steady pipelines of projects from the parent companies and the parent companies could replenish their capital through those sales.

Part of the rationale was that energy development is expensive and renewable energy projects do not have access to tax-advantaged financing mechanisms like master limited partnerships. Those partnerships have spurred the building of oil and gas infrastructure like pipelines over the decades. “This was an inventive twist on master limited partnerships, and provided some of the same benefits,” said Dan W. Reicher, executive director of the Steyer-Taylor Center for Energy Policy and Finance at Stanford. But, he said, they do not get all the tax benefits.

Nonetheless, for a while, the system proved attractive to investors, and analysts and clean-energy advocates predicted ever more activity and success in the sector. More than a dozen yieldcos have formed since 2013, and many have gone public, including 8point3 Energy Partners, a joint venture of First Solar and SunPower that raised $420 million in its initial public offering in June.

But as yieldcos proliferated — each with a hunger to bring in new projects to satisfy investor demand for growth — they drove up competition and prices for projects. Investors began to lose confidence that there would be enough projects to go around. In addition, the threat of rising interest rates made the yieldcos less attractive than more conventional financing. And depressed prices for oil and gas brought down energy values over all.

“Your growth story is only as good as your last project or your pipeline that you’re projecting,” said John J. Marciano III, a lawyer at Chadbourne & Parke who focuses on the development, financing, purchase and sale of energy and infrastructure projects and aviation equipment. “Once one started to go down, the others just probably followed the pack.”

Several analysts and executives attributed the declines to a mismatch between the investors — which include hedge funds looking for a relatively quick return — and the investments, intended to pay back over a long time. Others said investors who were losing money in oil and gas began dumping their renewable stocks to cover those losses.