The REED R8180 is a handheld solar irradiance meter built for checking photovoltaic panel performance and siting, reading solar power density up to 2,000 W/m2 (or in BTU/(ft2*h)) through a dedicated light sensor. It offers data hold and min/max capture on a 3.5-digit LCD, runs on a 9V battery, and is compact enough for routine field walk-throughs by solar installers and maintenance crews. Typical accuracy is on the order of +/-10 W/m2 or +/-5%, whichever is greater, under sunlight conditions.