Residential heat pump water heaters (HPWHs) are two to three times more efficient than conventional gas and electric resistance water heating options. While HPWHs have been available as energy-efficient alternatives that cut greenhouse gas (GHG) emissions – and improve local air quality – for the past 15 years, they represent less than 1% of the water heaters sold in California. According to contractors and installers, however, small increases are starting to happen.