Extech SP505 measures solar power level from outdoor sunlight to determine the best location for installations of solar panel and solar water heater.  It is also used indoors by window manufacturers, automotive industry, and remodeling home owners to check the level of solar radiation transmission through various glass thicknesses and degrees of tinting to use for window installations. Convenient pocket-sized meter with built-in precision solar light sensor is easy-to-use wherever you go.