The water consumption reductions from home solar installation in the United States

Installation of rooftop photovoltaic (PV) solar is expected to change the electricity landscape in the U.S. through reducing greenhouse gas emissions and mitigating global warming, as well as eliminating environmental impacts from fossil fuels utilization. Given the high-water intensity of fossil fuels, nuclear, and hydropower, the transition to solar and wind energy has important implications for also reducing the water footprint of energy production. This study evaluates the reductions in the water footprint from the electricity sector at the statewide and household scales in the contiguous U.S., as well as the expected virtual water footprint of individual homes upon switching to rooftop PV solar. Through integration of the water consumption intensity of the different energy sources that contribute to the current grid electricity, the annual residential electricity consumption, and the number of households, we have established a baseline for the variations of current statewide and household water consumption in the contiguous 48 states. The average nationwide water consumption of the residential sector from the current grid electricity is estimated as 9.84 × 10⁹ m³, while the household grid water consumption varies from 8 to 225 m³ y^-1 (a nationwide average of 66 m³y^-1). We estimate the household water consumption upon installing roof solar PV (3-60 m³ y^-1, a nationwide average of 4.7 m³ y^-1) and the expected annual reduction in water consumption (210 %-1600 %) at the household level across the U.S. The current electricity production from rooftop solar PV in the U.S. is currently about 1.5 % of the total residential electricity consumption, which infers an overall annual saving of 374 × 10⁶ m³ based on the average national grid water consumption in the U.S. The transition to rooftop PV solar infers not only reductions in greenhouse gas emissions coupled with a major reduction in the overall water footprint, but also a transfer of the water footprint and associated environmental implications to countries overseas where most PV panels are manufactured.