OG-300 certification is available for most solar thermal systems used to heat fluids such as water, glycol or air. It addresses systems used for heating, cooling, dehumidification and co- generation. While it may be used for commercial systems, many larger systems are unique and specifically designed for commercial application. Therefore, it is most commonly specified for residential domestic water heating systems by incentive programs. It does not apply to utility-scale systems or solar pool heating systems (see the OG-400 program which references ICC/APSP 902/SRCC 400 Solar Pool and Spa Heating Systems for certification of solar pool heating systems).