What a home energy score tells you

The Home Energy Score works like a miles-per-gallon rating for a house. An assessor walks through the home in under an hour and enters about 40 pieces of information into a federal scoring tool. The tool estimates how much energy the house is expected to use in a year and turns that into a score from 1 to 10. Single-family homes, townhouses and duplexes can be scored, and apartments and mobile homes can't.

What the number means

• A 10 ranks among the 10 percent of U.S. homes expected to use the least energy, after accounting for local climate.
• A 5 is expected to use about as much energy as an average U.S. home.
• A 1 is estimated to use more energy each year than 85 percent of U.S. homes, again after accounting for climate.

The score adjusts for climate using weather data. Two houses with the same score, one in a cold state and one in a mild state, perform about the same for their own weather.

What the score does and doesn't count

The score is an asset rating. It counts the home's fixed parts: the foundation, roof, walls, insulation and windows, how leaky it is, and the heating, cooling and water heating equipment. It leaves out lighting, electronics and appliances, and it ignores how the people living there run the house. A household that keeps the air conditioning very cold can still have high bills in a high-scoring home.

It also rates total energy use, not energy per square foot. With the same equipment and insulation, a larger house will generally score lower than a smaller one, because it has more surface to lose energy through.

A low score doesn't mean a house is poorly built. A well-equipped house can score low because it's large or under-insulated, and the score shows how much room there is to improve.

The three parts of the report

• The score. The 1 to 10 rating itself.
• Home facts. Everything the assessor collected about the shell, the heating, cooling and hot water systems and the floor area, along with the estimated energy use by fuel type.
• Recommendations. Improvements expected to pay back in 10 years or less, at state average utility rates and national average installation costs, with estimated yearly savings. A "score with improvements" shows what the house would score with all of them done. An assessor may add others that reflect local rebates.

Getting a score

The score is offered only where an official Home Energy Score partner works, such as a utility, a state or local government, or a nonprofit. The program's partner map and Find an Assessor tool show who offers it by zip code. The price varies, and it's often built into a home energy audit or inspection. If no partner covers your area, the local utility or state energy office may know when one will.

When buying, ask whether each home you're considering has a score. When selling, a real estate agent can check whether the score can go in the local listing.

An annotated example

What to do next

Ask the seller whether the home has a Home Energy Score, and if it doesn't, find an assessor on the program's partner map. Keep the report with the home's records.