The Arizona Registrar of Contractors does have a specific plumbing license which includes solar water heaters. R-37 is required for contractors installing or performing maintenance on residential solar water heaters, and C-77 or C-78 are required for commercial solar water heaters. License classifications CR-77 and CR-78 cover both residential and commercial applications of solar water heating.
The Registrar of Contractors also has licenses for contractors who work on space heating and cooling systems, which includes solar thermal systems. R-39 is required for contractors installing or performing maintenance on residential solar space heating and cooling systems, and C-79 is required for commercial systems. License classification CR-79 covers both residential and commercial applications of solar space heating and cooling.
Lastly, the Registrar of Contractors has licenses for contractors installing or performing maintenance on pools which includes solar pool heating systems. B-06 is required for contractors working on residential pools, and A-19 is for commercial pools. KA-6 allows a contractor to work on both residential and commercial pools.
All contractors who work with solar energy systems must have four years of relevant work experience and must pass an exam in order to receive a license in Arizona. The following licensing exams include sections on solar applications: air conditioning and refrigeration, boilers, steam fitting and process piping, swimming pools, and general plumbing.