REC Solar, a San Luis Obispo-based designer and installer of solar electric systems, is celebrating its 15th anniversary this year.

The company was founded in 1997 by Judy Staley and Fred Sisson and now has more than 800 employees with 17 offices in six states, according to a recent news release.

REC Solar is a subsidiary of Mainstream Energy Corp.

REC Solar has installed 118 megawatts of solar in both residential and commercial projects — consisting of more than 8,700 installations in 16 states.

From 1997 to 2006, REC Solar installed five times as many megawatts of residential than commercial solar. But as of recent months, the company has installed twice as much commercial as residential solar overall.