HERS Index Calculator

Formula

The formula to calculate the HERS Index Score is:

\[ \text{HERS Index Score} = \left(\frac{\text{Reference Home Energy Consumption} - \text{Rated Home Energy Consumption}}{\text{Reference Home Energy Consumption}}\right) \times 100 \]

Where:

\(\text{HERS Index Score}\) is the Home Energy Rating System Index Score.
\(\text{Reference Home Energy Consumption}\) is the energy consumption of a standard reference home (in BTUs).
\(\text{Rated Home Energy Consumption}\) is the energy consumption of the rated home (in BTUs).

What is a HERS Index?

The Home Energy Rating System (HERS) Index is a standard measurement used in the United States to assess a home's energy efficiency. A lower HERS Index score indicates a more energy-efficient home. The scale is set such that a home built to the specifications of the HERS Reference Home scores a HERS Index of 100, while a net zero energy home scores a HERS Index of 0. The HERS Index score is used by homebuyers, builders, and mortgage lenders to gauge a home's energy efficiency and potential energy costs.

Example Calculation

Let's consider an example:

Reference Home Energy Consumption: 100,000 BTUs
Rated Home Energy Consumption: 80,000 BTUs

Using the formula to calculate the HERS Index Score:

\[ \text{HERS Index Score} = \left(\frac{100,000 - 80,000}{100,000}\right) \times 100 = 20\% \]

This means the rated home is 20% more energy-efficient compared to the reference home.