The sale premium varies substantially by market. In Riverside, Calif., for example, homes with solar-energy systems sold for 2.7% more than comparable homes without solar power—a markup of $9,926 for the median-valued home in the metro. In the greater New York City metro, solar-powered homes have a premium that is double that of Riverside. At 5.4%, that’s an extra $23,989 in value for the typical home in New York.