For solar water heating systems, the solar fraction is the ratio of solar energy to total energy delivered to the water storage tank. The solar fraction is based on the energy values for year one of the project cash flow.

Solar Fraction

Solar Fraction = Q auxiliary only (kWh/year) ÷ System Energy (kWh/year)

System energy is the sum of the time series System power generated output, and represents total electricity saved by the system, and Q auxiliary only is the energy that would be delivered to the tank without the solar collector. See the Solar Water Heating Results for details.

Note. SAM assumes that the solar water heating system does not export energy. For any time step that "system power generated" is greater than the load defined on the Electric Load page, it sets system power generated equal to the load.