When your old hot water system fails, you have an opportunity to upgrade to a more advanced, energy efficient appliance. Two popular options for eco-friendly hot water are heat pump units and solar water heaters. Both use renewable technology to cut energy consumption and costs versus traditional tanks. To pick the best green solution for your home, compare heat pumps versus solar power based on efficiency, upfront expenses, maintenance, warranties, longevity, environmental benefits, suitable climates, and more.