The Home Energy Score is an asset rating for homes, developed and administered by the U.S. Department of Energy. After conducting a brief walk thru of a home, a qualified assessor calculates a home's score on a 10 point scale using a standard scoring tool, with 10 reflecting homes that use the least amount of energy assuming standard operating conditions (US DOE). The Home Energy Rating System (HERS) index is a measure of a home's energy efficiency. It can also be used to inspect and calculate a home's energy performance. The lower a home's HERS Index Score, the better its efficiency.