NIPTON, Calif. — The Ivanpah solar power plant stretches over more than five square miles of the Mojave Desert. Almost 350,000 mirrors the size of garage doors tilt toward the sun with an ability to energize 140,000 homes. The plant, which took almost four years and thousands of workers assembling millions of parts to complete, officially opened on Thursday, the first electric generator of its kind.

It could also be the last.

Since the project began, the price of rival technologies has plummeted, incentives have begun to disappear and the appetite among investors for mammoth solar farms has waned. Although several large, new projects have been coming online in recent months — many in the last quarter of 2013 — experts say fewer are beginning construction and not all of those under development will be completed.

“I don’t think that we’re going to see large-scale solar thermal plants popping up, five at a time, every year in the U.S. in the long-term — it’s just not the way it’s going to work,” said Matthew Feinstein, a senior analyst at Lux Research.

“Companies that are supplying these systems have questionable futures. There’s other prospects for renewables and for solar that look a lot better than this particular solution,” he said, including rooftop solar systems that are being installed one by one on businesses and homes.