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HERS Testing: What Is It and When Is It Necessary?

Updated Oct 20, 2022

Updated Oct 20, 2022

Home > Maintenance & Renovation > HERS Testing: What Is It and When Is It Necessary?

Home Energy Rating System (HERS) testing examines a home’s energy efficiency and notes areas where energy efficiency can be improved. Though HERS testing is performed throughout the United States, it’s required in California. HERS testing is especially important when you’re buying or building a new home and need to determine how much you’ll spend on utility bills. Let’s take a look at what this test involves to how a HERS rating is calculated.

What is HERS testing?

Born out of the California HERS program that addresses construction defects and improper equipment installations, HERS testing determines the energy efficiency rating of a home on a scale from 0 to 250 and whether all major systems and appliances meet the energy efficiency state standards. HERS testing takes between two to four hours and is performed by a HERS rater—a certified professional that inspects the home, evaluates different features, and determines the home energy rating.

What is a HERS rating?

A HERS rating is based on the HERS Index, an industry standard developed by RESNET (Residential Energy Services Network) by which a home’s energy efficiency is measured. The HERS Index is based on a scale from 0 to 250. The lower the number, the more energy efficient the home. This relative rating is provided after HERS testing is completed and gives homebuyers or homeowners insight as to how the home ranks on an energy efficiency scale.

The US Department of Energy (DOE), the Department of Housing and Urban Development (HUD), and the Environmental Protection Agency (EPA) recognize the HERS Index as an official verification of home energy performance.

How is a HERS rating calculated?

A HERS rating is calculated after a HERS rater completes a HERS testing on your home. To calculate the rating, a HERS rater will come to your home to assess its energy efficiency and compare data from your home to a reference home—a designed-model home of the same size and shape (this is to ensure your score is always relative to the size, shape, and type house you live in).

The HERS rater will then provide a relative performance score based on the industry-standard HERS Index.

A home energy rating is based on visual inspection and diagnostic testing of the physical characteristics and energy efficiency features of your home. Here are some features evaluated during a HERS testing.

  • Ceilings and roofs
  • HVAC system
  • Air leakage in the home
  • Vents and ductwork
  • All exterior walls
  • Floors over unconditioned spaces, like your garage

What to expect during HERS testing

Here are three of the most common tests you’ll have performed during a HERS testing.

  1. Duct leakage testing—A duct test measures the amount of air leaks in unconditioned areas from the duct system.
  2. Refrigerant charge verification—This test measures how well your air conditioning system performs and verifies that refrigerant levels meet manufacturer specifications.
  3. Airflow verification—Used in conjunction with the refrigerant charge verification, this test measures the velocity of air flowing through your duct system during the air conditioning cycle.

When is HERS testing necessary?

HERS testing should be done when selling, buying, or building a home. When you’re selling a home, HERS testing can help determine the resale price. When buying a home, HERS testing helps you anticipate the cost of future energy bills and makes clear what types of efficiency upgrades will be necessary. When building a home, HERS testing ensures that your major appliances and systems meet energy efficient standards.

All California homeowners and contractors are required to comply with the requirements of the California Code of Regulations Title 24, Part 6, Energy Efficiency Standards for Residential and Nonresidential Buildings to meet the state’s energy goals and requirements.

Additionally, homeowners in California are required to schedule a HERS testing whenever a new mechanical system that requires verification or testing is installed in their home. This is part of Title 24, Part 6 of the HERS Program formed by the California Energy Commission to differentiate the energy efficiency levels among California homes and guide investment in cost-effective home energy efficiency measures.

HERS testing and home warranties

If you’re buying or building a home, we recommend exploring home warranty options in conjunction with HERS testing. While HERS testing will ensure your systems and appliances are as energy efficient as possible during the homebuying or homebuilding process, a home warranty will protect you in the event that one of these systems or appliances breaks down.

Additionally, if one of your systems or appliances does break down, your home warranty provider will likely check to see if you had a HERS testing performed either before you bought the house or after you installed appliances in the house. If you didn’t have HERS testing performed, your home warranty provider may not cover the cost of a system replacement. For this reason, we highly recommend scheduling a HERS testing and buying a home warranty to protect your investment.

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