The Bay Area remains the epicenter of cleantech in the United States, according to a second annual report set to be released today by Clean Edge, a cleantech research and publishing firm.

An analysis of job listings, venture capital investment and patent registration found that the Bay Area -- for the second year in a row -- is the No. 1 metro region in the country for cleantech jobs, followed by Los Angeles, Boston, New York and Denver.

The report is meant to show not only where cleantech jobs exist today but also which regions can expect cleantech employment growth in the future.

Some regions have begun to specialize. The San Diego area, home to companies like Synthetic Genomics and Sapphire Energy, is becoming a hotbed for biofuels, while Houston is home to several multinational wind energy developers.

By contrast, the Bay Area is home to leading cleantech companies in almost every sector, including biofuels, electric vehicles, lighting, solar and smart grid.

"California is the epicenter of cleantech in the United States, and the Bay Area is the hub of the epicenter," said Ron Pernick of Clean Edge.

Several companies in the region are hiring at rapid paces. Tesla Motors in Palo Alto has more than 800 employees and expects to be above 1,000 by the end of the year. Silver Spring Networks, a Redwood City-based smart grid company, has dozens of engineering positions listed on its website. Solar companies like SunRun and SolarCity are also rapidly expanding and racing to fill several openings.

But competition from China is increasingly fierce. The Clean Edge report noted that its list of the top 10 cleantech employers worldwide includes six Chinese companies. Vestas Wind Systems of Denmark, with more than 20,000 employees, is the largest cleantech employer, followed by LDK Solar and Suntech Power, both of China. Only two American companies made the list: Itron, a smart grid company based in Washington state that has more than 9,000 employees, and Baldor Electric of Fort Smith, Ark.

China has set a national target for renewable electricity, calling for 15 percent of the country's energy to be procured from nonfossil fuels by 2020. In the United States, Sen. Jeff Bingaman, D-N.M., has introduced a bill that would require utilities to purchase at least 15 percent of their electricity by 2021 from renewable-energy resources such as wind, solar, geothermal and hydropower, but it's not clear if the bill has the 60 votes needed to pass.

Contact Dana Hull at 408-920-2706. Follow her at Twitter.com/danahull.

top 15 metro areas for cleantech jobs
1. San Francisco Bay Area
2. Los Angeles/Long Beach
3. Boston/Cambridge
4. New York
5. Denver
6. Washington, D.C.
7. San Diego
8. Houston
9. Chicago
10. Austin
11. Seattle
12. Atlanta
13. Dallas/Fort Worth
14. Portland, Ore.
15. Sacramento
Source: Clean Edge