What is a HERS Index Score?

Using the Home Energy Rating System

HERS is short for Home Energy Rating System and is a process of evaluating the energy efficiency of a home. Without it, it’s just a guess on whether or not a home will perform well or cost you money. To earn a HERS Index score, there are many mandatory standards the home needs to comply with, such as window sealing, insulation, and wall sealants.

The HERS Index Score is based on a scale from 0 to 150, with 0 being a net-zero energy home (where the home generates as much energy as it consumes) and 150 being a home built to the minimum standards of the 2006 International Energy Conservation Code (IECC). The HERS Index Score is determined by a professional energy auditor who conducts a detailed analysis of the home's energy consumption, including a physical inspection of the home, a review of the construction plans, and a review of the home's energy systems and appliances.

An independent certifier will first evaluate the house plans and provide feedback along with an estimated HERS Index Score. The certifier physically inspects the house at least twice. The first visit is when the insulation is being installed to ensure it is being done properly. The second visit is when the home is complete. At this point, the certifier makes a general visual observation and then tests the home for “tightness” by performing a blower door test. A blower pressurized the home and a test meter measures how well the home holds the pressure. The lower the score, the better, just like the HERS Index Score. Typical new construction homes are estimated to score at 100. A HERS Index Score of 50 would indicate that the home is 50% more energy efficient than a typical new construction home.