SAN FRANCISCO  The sun is starting to grow jobs.

While interest in alternative energy is climbing across the United States, solar power especially is rising in California, the product of billions of dollars in investment and mountains of enthusiasm.

In recent months, the industry has added several thousand jobs in the production of solar energy cells and installation of solar panels on roofs. A spate of investment has also aimed at making solar power more efficient and less costly than natural gas and coal.

Entrepreneurs, academics and policy makers say this era’s solar industry is different from what was tried in the 1970s, when Jerry Brown, then the governor of California, invited derision for envisioning a future fueled by alternative energy.

They point to companies like SolarCity, an installer of rooftop solar cells based in Foster City. Since its founding in 2006, it has grown to 215 workers and $29 million in annual sales. “It is hard to find installers,” said Lyndon Rive, the chief executive. “We’re at the stage where if we continue to grow at this pace, we won’t be able to sustain the growth.”