Equation 1 – Solar water system size

Estimate collector size using the following equation:

The paper “Annual System Efficiencies for Solar Water Heating” by Craig Christensen of National Renewable Energy Laboratory and Greg Barker of Mountain Energy Partners presents calculated efficiency for domestic solar water heaters that varies between 26.4% and 44.3% depending on location and hot water load with an average of 40.2% for all locations and load profiles.