• Sean

HERS Ratings help, whether you're building, buying or selling a house

Updated: May 2, 2019

If you’re buying a home, HERS is a great way to evaluate long-range energy costs and maximize comfort. When selling a home, the HERS rating can be a valuable marketing tool to attract buyers and optimize the return on your investment.

What is a HERS rating and why should you care about it?

Simply stated, a HERS (Home Energy Rating System) assessment is a comprehensive measurement of the home’s energy performance. If you’re building a new home, the HERS standards provide excellent guidelines for making energy-efficiency upgrades.

A HERS assessment is also an extremely helpful tool that homeowners can use to enhance the energy performance of an existing residence. It’s probably the best way to evaluate a home’s energy usage and determine the most cost-effective measures for improving efficiency.

Here’s how it works: The HERS score compares the energy efficiency of a home to a similarly-sized residence built to code. The lower the score, the more efficient the home. A score of 100 means the rated home has the same energy usage as a similar HERS Reference Home. A score of 70 means the home is 30 percent more efficient than a similar HERS Reference Home.

Thus each one-point change on the HERS rating represents a 1 percent change in energy efficiency.

A HERS Index rating of 0 means the home produces the same amount of energy that it uses. This can be accomplished by installing photovoltaic (solar energy) panels or other renewable energy systems while optimizing the efficiency of the appliances, HVAC and other equipment.

After mortgage payments and property taxes, utility bills are the third-largest monthly cost for the typical homeowner – and the only one over which the homeowner has some sort of control. On average, energy and water bills account for nearly 20 percent of the total cost of owning a home.

Below we’ll explain what a HERS rating is, how it is calculated and what benefits can be derived from this type of assessment.

Who developed HERS?

The Home Energy Rating System was created by the Residential Energy Services Network (RESNET), an independent, nonprofit organization that helps homeowners reduce their utility bills by achieving greater energy efficiency.

RESNET is the certifying board for all HERS raters. The HERS rating underpins all major energy efficiency certifications.

Founded in 1995, RESNET has developed national training and certification standards for HERS raters and home energy professionals, who are recognized by federal government agencies such as the Department of Energy, the Environmental Protection Agency and the US mortgage industry.

In addition, RESNET oversees the training and quality assurance of the HERS program.

In calculating the HERS Index, energy professionals make use of the latest technological advances in energy-efficiency assessment. This is an ongoing process; the tools, methodologies and analysis are constantly being updated as the science of energy efficiency becomes more sophisticated. In order to solicit feedback from industry experts, there is a formal public review and commenting process.

What’s involved in the HERS assessment?

It’s a lot like an annual checkup by your family physician. The entire house is examined, including:

  • All exterior walls (above and below grade)

  • Floors over unconditioned spaces (such as garages or cellars)

  • Ceilings and roofs

  • Attics, foundations and crawlspaces

  • Windows and doors, vents and ductwork

  • HVAC system, water heating system and thermostats

The collected data is very specific and includes basic information about the home, such as style, age, square footage, number of bedrooms, measurements of walls and ceilings, and types of flooring. Construction details are also very important. The types of walls and the condition of the foundation, ceilings, attic and basement are critical factors.

Other elements that can influence home performance include the style, size, orientation and features of windows (such as the number of glass layers) as well as the age, type and thickness of wall insulation.

HVAC and water heating systems are comprehensively evaluated. Equipment manufacturers, model numbers, type of fuel, equipment location and heating zones all provide important pieces of information in the overall energy picture. It’s also useful to look at billing records and the names of electric utility and oil or gas dealers.

The HERS Rater will conduct a series of diagnostic tests using specialized equipment to determine air leakage, efficiency of the HVAC system and effectiveness of the home’s insulation. Some of the equipment typically used includes a blower door, duct leakage tester and infrared cameras.

Blower door test

The blower door makes use of a powerful fan that mounts into the frame of an exterior door. As the fan pulls air out of the house, the air pressure inside lowers. This enables the higher air pressure from the outside to flow into the house – through unsealed cracks and openings. A smoke pencil is sometimes used to detect leaks.

In addition to wasting energy used to heat and cool the home, air leakage can also cause moisture condensation, uncomfortable drafts and a decrease in air quality.

Duct blaster test

Testing duct tightness with a duct blaster is a big step in measuring a home's energy efficiency

A duct leakage test uses a calibrated fan to pressurize the duct system and then measure the airflow through the fan with the duct system at operating pressure. Duct leaks can send conditioned air into spaces that don’t require heating or cooling, thus wasting energy. These types of leaks can also draw unconditioned air into the HVAC system, making it work harder.

Infrared camera

The infrared camera produces easy-to-read thermal images that identify air leaks and insulation defects by allowing the HERS Rater to view differing temperatures in a specific area of the home.Although floors, walls, ceilings, doors, ducts and windows are the primary culprits for leaking air, there are a number of other areas that can contribute to leaks. These include electrical outlets, lighting fixtures, plumbing penetrations and fireplaces.

By using these diagnostic tools collectively, HERS Raters can generate an accurate picture of the tightness of the home and pinpoint areas that can be readily repaired.

How is the HERS score calculated?

The actual calculation of the score utilizes a formula that takes into account several factors, including:

  • Energy consumption

  • Water heating

  • Energy used for lighting

  • Energy used for selected appliances

  • Amount of energy that is purchased

A computer program analyzes the data and totals up points for each item. The final report provides an overall assessment of home energy usage and also pinpoints specific areas that can reduce consumption.

The HERS assessment computes the average monthly energy costs of the home, taking into account the fuels used and local utility pricing. Hard copies of the Energy Rating sheet and all supporting documentation are mailed to the homeowner. This information can also be sent to other interested parties, such the lender, builder, buyer, seller or realtor.

HERS is a performance-based rating system that is flexible in meeting energy standards. All of the data from the assessment is taken into account and the final rating represents a conglomeration of many factors. So if your goal is to reduce energy consumption, there can be many avenues to choose.

The cost of upgrades, payback periods and overall comfort are all important considerations. Another factor is how long you intend to stay in the home.

Understanding a HERS score

After collecting and analyzing all the data, a certified Home Energy Rater determines the energy efficiency of the home, assigning it a HERS Index Score. This number is a relative figure and is compared to a RESNET “reference home,” one with the same size and shape as the assessed home.

Basically, a lower the number indicates greater energy efficiency. According to the US Dept. of Energy, a typical resale home scores 130 on the HERS scale; a home built to the 2004 International Energy Conservation Code (IECC) gets a rating of 100.

The IECC is a comprehensive, stand-alone residential code that encourages energy conservation through efficient design, mechanical systems and lighting as well as the use of new materials, techniques and technologies. State energy codes are frequently based on a version of this code although some states have no such requirements. Some may have an energy code only as a recommended practice.

Thus a home with a HERS rating is 70 is 30 percent more efficient than the RESNET reference home. A home with a HERS score of 130 uses 30 percent more energy than the RESNET reference home.

The HERS score is similar to the MPG rating of an automobile. It lets the homeowner know how the house is performing in terms of energy usage. If utility bills are high, the problem might not be overusing heating/cooling and electricity. It could be a performance issue with the home itself and the HERS report can zero in on the areas of potential improvement.

Common upgrade targets

You can improve your HERS score 20-40 points by taking the simple steps below:

  • Replace incandescent light bulbs or CFLs with LEDs. Incandescent lamps are no longer being manufactured but you still might have some in the home. LEDs may be more expensive but they use half the electricity of a comparable CFL and 12 percent of the energy of an incandescent. Plus, they last much longer. The average lifespan of an LED (comparable to a 60-watt incandescent) is 25,000 hours, compared to just 1,200 for the incandescent and 8,000 for a CFL. Potential savings: 2-3 points.

  • Insulate the attic. Actual energy reduction depends on the quality of the existing insulation. Potential savings: 3-15 points.

  • Insulate the crawlspace. Potential savings: 2-3 points.

  • Insulate the rim joist. A common source of energy leaks in older homes, the rim joist is the edge of the wood floor framing system. It’s located on top of the foundation walls. Potential savings: 3-5 points.

  • Air seal can lights. Recessed cans are a significant source of air leakage but this repair has to be done carefully since can lights are known to overheat if not insulated properly. Older fixtures are more likely to cause problems because some of them are not equipped with thermistors, devices that cut off the power supply if the unit overheats.

PRO TIP: There are actually air tight LED replacement trim kits…they’re air tight AND the install is super easy

  • Upgrade to an energy-efficient furnace. Annual Fuel Utilization Efficiency (AFUE) is the industry marker for furnace efficiency and the federal minimum is 80 percent. A rating of 90 or above is considered energy efficient. Furnaces with AFUEs of 95 to 98.7 percent are currently available on the market. Potential savings: 5-15 points.

Benefits of the HERS rating

Having a greater understanding of the home’s energy performance, and being able to quantify it, has many benefits for homeowners as well as homebuyers, sellers, real estate professionals and contractors. The HERS score provides specific guidelines for reducing energy (and saving on utility bills) and can also be used as an effective marketing tool.


  • For homeowners, the most important aspects of home energy performance are energy bills and comfort. A drafty home not wastes energy but it’s often uncomfortable – too cold in the winter and too hot in the summer. Sometimes the temperature, and comfort level, can vary from room to room.

  • Inefficient energy usage can also result in health issues. Reduced air quality and mold can be caused by antiquated and poor-performing HVAC and water heating systems.

  • A HERS rating report offers specific details about the cause of the problems – and potential solutions. The cost and payback period of the corrective measures are also calculated so the homeowner can prioritize work projects and get the most bang for the buck.

  • The payback period is the amount of time it takes for the energy savings to offset the cost of the upgrades. In many cases, this can be two years or less

  • By learning how your home performs energy-wise, you can start saving money and being more comfortable. Not only that, you’ll be doing something to help the environment. By decreasing your use of fossil fuels and electricity, you’ll be reducing pollution and the effects of climate change. It’s a great investment all around.

  • Keep in mind that some states offer rebates for energy-efficiency upgrades. Check with your local utility to find out about what may be available in your area.


  • For a homebuyer, purchase of a home is one of the most important – not to mention nerve- wracking – decisions her or she has to make. Factoring in the energy costs over the expected duration of residence provides a true cost of ownership.

  • The monthly energy bills, including maintenance costs, can be a determining factor in whether you can actually afford your dream home. The HERS score also gives you valuable information when comparing several homes.

  • In addition, some buyers prefer energy-efficient homes for the above-listed environmental reasons. A detailed energy assessment can also alert a potential buyer about problems that could become costly over the long haul.

  • Either way, it makes sense to know what you’re buying and how much it’s going to cost over the long haul.


  • As we’ve learned more and more about energy efficiency and climate change in recent years, a growing segment of homebuyers are finding this to be an attractive selling point when purchasing a property. A low HERS rating can be an important marketing tool when selling your home.

  • The prospects of lower utility bills, added comfort and responsible environmental stewardship make for a convincing sales pitch, one that can increase your asking price. Several years ago, the National Association of Home Builders (NAHB) commissioned a study of the most important features for homebuyers. Four of the top 10 features – appliances, windows, home energy rating and ceiling fans – involved energy efficiency.

  • With a HERS rating score, sellers can highlight energy-saving features, project energy savings and emphasize the additional comfort of an efficient home – and back it up with numbers and facts.

  • Real estate professionals

  • Because real estate agents represent buyers and sellers, they can reap all of the above benefits from a HERS rating. Agents can help prospective buyers determine what properties might represent the best value and also project long-term energy expenses, providing an accurate breakdown of the true cost.

  • For sellers, real estate professionals use the HERS score as a marketing tool, enabling them to optimize the selling price of the home.


  • A HERS rating shows how well designed and built a home is. Getting HERS scores for the homes you build will give you a tangible, 3rd party verified score that proves the quality of your work. If you’re building high-quality homes why not get credit for it and be able to show future customers and prospects exactly how good you are.


Utility bills account for nearly 20 percent of the monthly cost of home ownership and energy-efficiency upgrades can dramatically reduce these expenditures. At the same time, decreasing energy consumption is also good for the environment, reducing the discharge of toxic pollutants into the atmosphere.

For these reasons, homeowners are willing to invest money into energy-efficiency upgrades and home buyers see this as a value proposition. Those who are selling their homes can use energy efficiency as a marketing tool.

A HERS rating is an excellent way to determine the energy-efficiency of a home and provide a detailed road map for making cost-effective improvements.

For additional information about HERS assessments, call Revive Energy at 615-398-9096.


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