Home Energy Rating System (HERS) Explained
The Home Energy Rating System, aka the HERS index, is a nationally recognized system used to determine and verifiy a home’s Energy Performance.
HERS is the building industry’s gold standard by which a home’s energy performance is measured. The HERS index was developed by the Residential Energy Services Network (RESNET). A home’s HERS rating is based on an inspection and testing by a certified RESNET Home Energy Rater. When designing a new home, a HERS rating can be targeted, and then the home’s plans can be modeled to estimate its likely HERS rating. However, a home’s official HERS rating is based on the RESNET certified inspection and testing.
BPC Homes Earn Exceptional HERS scores
All BPC Green Builders homes are HERS rated by third parties to verifiy the HERS scores they achieve. There is a preliminary HERS score projection conducted via computer modeling during design and prior to construction. Upon completion the home is field tested to determine its as-built HERS score.
What the HERS Index Score Specifically Represents
The HERS rating of Energy Performance factors in two elements:
- The home’s Energy Efficiency or how little energy it takes to operate the home.
- The amount of Clean Energy the Home Generates such as with solar panels, passive solar energy or wind energy.
The HERS Index Basline Score is 100
The key point to remember: The lower the HERS rating, the better the home’s energy performance
HERS Rating of 150: A home with a 150 HERS rating uses 50% more energy than a new home built to standard energy code. Most older homes will rate above to way above 100 on the HERS index. Some older homes can exceed HERS index scores of over 200.
HERS Rating of 100: A new home constructed and tested to meet the current building code standard for home energy efficiency will rate 100 on the HERS index.
Rating 100 does not mean the home is considered to be energy efficient from a green building standard, only that it meets the code standard code, which is the lowest acceptable level of energy efficiency allowed by code.
HERS Rating of 50: A HERS rating of 50 means your home uses 50% less the energy than a new home built to code and, on average, 80% less than a resale home uses.
HERS Rating of 0: A 0 (zero) HERS rating means the home uses no net energy. A home with a 0 HERS index is also called a Net Zero Home or Zero Energy Home. To achieve this rating, a home generally needs to use some form of solar or wind energy generation. The home must also be connected to the power grid and use Net Metering.
HERS Rating of -10: Some homes are so energy efficient they generate more clean energy than they draw from the grid. A negative rating represents the additional clean energy the home is putting back into the grid, based on the scale of 100 for what a standard new home uses. Each negative point (-1, -2, -3, etc.) represents 1% of what a normal new home would use being returned to the grid.
It’s strange, but a home with a Negative HERS rating is called a Positive Energy Home.