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HERS index score rating explained: How can it save you money?

From solar panels to LED light bulbs to low-flow shower heads, there are plenty of ways to reduce your energy consumption. A HERS score is often the first step to figuring out cost-effective fixes.

At some point in the home buying or selling process, you may have heard of the HERS Index or HERS scores. What do these scores mean? Does your home need one? Should you ask about the HERS score of a home you’re thinking of buying? And can a good HERS score really save you cash?

What is a HERS score?

HERS stands for Home Energy Rating System. The HERS Index, launched in 2006 by the Residential Energy Services Network (RESNET), calculates a home’s energy efficiency. It’s become the industry standard for judging the energy performance of a house.

HERS scores are designed for new homes (or homes after a complete renovation). When builders need to meet efficiency standards, they use the HERS Index.

To get a HERS score, a house needs to be inspected by a certified RESNET rater. The process is extensive. The rater comes prepared with equipment. The inspection and assessment typically cost between $1,500 and $3,000, so it’s an investment. But energy improvements toward a good HERS score save homeowners more in the long run.

Here are some of the energy “bugs” the rater looks for:

  • Air leaks in the building envelope
  • Heating, ventilating, and air conditioning (HVAC) distribution duct leaks
  • Any combustion risks
  • Air infiltration rate

Some of the most common offenders are air leaks which let heat escape, requiring residents to use more energy heating the home. A process called thermographic imaging can show you exactly which spots are leaking energy.

The rater also checks:

  • Wall and ceiling insulation
  • Water heating systems
  • Thermostats
  • Foundations
  • Attics and crawl spaces

How do HERS scores work?

After inspecting the home and running the data through specialized software, the rater assigns a HERS score on a scale of 0 to 150. The lower the number, the better the score. Each one-point change in a score, up or down, represents a one percent shift in energy efficiency.

To get an accurate score the rater compares the home to a standard Reference Home. The Reference Home isn’t an actual house, just an analysis tool, but it resembles the rated home as much as possible—same size, shape, environment, and climate. This means your score is relative to the type of house you live in.

Net zero score

A HERS score of 0 or a “net-zero” home produces or conserves as much energy as it uses. Your home probably won’t get this score (don’t worry, it’s not expected).

Average HERS score

A HERS score of 100 is average for a newly built home where residents haven’t started using energy yet. This means the home is exactly as efficient as the Reference Home.

A HERS score of 130 is average for a home that’s been lived in or a resale home.

What is a “good” score?

Anything at the average rate or below (100 for a new house, 130 for a lived-in house) is pretty good. A score of 100 indicates a new house is built to code. It’s even better to score below the average. A higher-than-average score means the home can use a few fixes.

RESNET’s score guide and interactive chart can tell you more about what a specific score means.

Fortunately, the HERS rating process does more than issue a number; it shows where homeowners can make improvements. The rater will provide a cost/benefit analysis of recommended upgrades and the estimated amount of energy each upgrade will save. And saving energy usually translates to saving cash.

Why is a good HERS score important?

An energy-efficient home isn’t just better for the environment. It’s more comfortable and cost-effective for residents. A home that conserves heat, for example, will be much easier to live in come winter.

If you’re a homeowner

Though HERS scores are designed to assess brand new homes, you can get a score for a lived-in home to see how well it’s operating. You might discover the home is leaking energy in places that never occurred to you to check.

If you’re selling a home

Low HERS scores are fantastic for a home’s resale value. Homes with low HERS scores and good energy efficiency can command a higher price—up to 30 percent higher than similar, less efficient homes.

If you’re buying a home

Yes, you may pay a little more initially for a home with a good HERS score. But over time, the energy savings should more than make up for it. And you’ll know exactly what you’re buying.

The HERS report for a new home estimates the cost of utility bills and efficiency upgrades, giving you an accurate picture of how much you’ll be spending. The lower the score, the fewer upgrades you need. A lower score also lowers your projected utility bills significantly.

How can a good HERS score save you money?

After mortgages, the biggest expenses homeowners face are usually climate control-related: heating, cooling, and water heating. Naturally homeowners are on the lookout for ways to bring these costs down.

ENERGY STAR certified homes (a slightly different process than the HERS index, but measuring the same factors) have saved their owners a combined $20 million in energy costs, according to the Department of Energy (DOE). A good HERS score is the first step to getting a home eligible for ENERGY STAR certification.

As a bonus, one report found homeowners with low HERS-score homes are less likely to default on their mortgage.

How to get your home HERS-ready

Whether or not you choose to get a new home HERS-rated, you can conserve energy with a number of fixes around the house. The DOE has a site full of guidelines for energy-conscious homeowners to get you started.

Air seal windows

Air leakage from windows and drywall is one of the biggest drains. Older houses built before World War II are more likely to leak.

Seal any gaps with high-quality tape or silicone caulk

Cover the windows with shrink film to keep the heat inside. Adding weather stripping to windows and doors is another major energy saver.

You may not have to shoulder the whole cost yourself, since many states offer weatherization assistance programs for households below a certain income threshold.

Add (or fix) insulation

Insulation keeps heat from moving through walls, ceilings, and floor—locking warm air inside during the winter and keeping it out during the summer.

This is especially important in attics and basements, the places most likely to have holes allowing pipes and wiring into the home.

Tweak the thermostat

Lowering the temperature 10 degrees on the thermostat can save as much as 10 percent of heating and cooling costs. Even a five-degree drop makes a difference.

Your best bet is an automatic thermostat, which regulates the temperature for you.

Upgrade heating and cooling systems

Keeping your heating, ventilation, and air conditioning systems (known as HVAC systems) in good working order can save a ton of cash. Get an annual tune-up for furnaces and air conditioning, and upgrade as needed.


From solar panels to LED light bulbs to low-flow shower heads, there are plenty of ways to reduce your energy consumption. A HERS index rating is often the first step to figuring out cost-effective fixes.

About the author


Amy Bergen

Amy is an educator, editor and writer. She understands finances are challenging but believes they don't have to be terrifying. Amy has covered topics from investing to student loans and money management for the millennial set.

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