Depending on your area, the simplest way to find a solar thermal systems contractor is to look in the yellow pages under “Solar Energy Equipment and Systems—Dealers.” Most of the listings will probably be for solar water heating, photovoltaic (solar electric), or electric systems contractors.
You can also contact your utility company to get information on recommended vendors, or search on the Internet for solar water heating, solar pool heating, or solar space heating, depending on the application you are interested in installing.
Your state may have an active chapter of the Solar Energy Industries Association (SEIA), a trade association of contractors, distributors, and manufacturers. See “Getting help” for contact information.