Enter the Reference Home Energy Consumption and Rated Home Energy Consumption into the calculator to determine the HERS Index Score. This calculator can also evaluate any of the variables given the others are known.

## Hers Index Formula

The following formula is used to calculate the HERS Index Score.

HERS Index Score = (Reference Home Energy Consumption – Rated Home Energy Consumption) / Reference Home Energy Consumption * 100Variables:

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

To calculate the HERS Index Score, subtract the Rated Home Energy Consumption from the Reference Home Energy Consumption. Then, divide the result by the Reference Home Energy Consumption. Multiply the quotient by 100 to get the HERS Index Score.

## 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. It is a scoring system where a lower score indicates a more energy-efficient home. The index is based on a scale where 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 as a reliable way to gauge a home’s energy efficiency and potential energy costs.

## How to Calculate Hers Index?

The following steps outline how to calculate the HERS Index Score:

- First, determine the Reference Home Energy Consumption (in BTUs).
- Next, determine the Rated Home Energy Consumption (in BTUs).
- Next, use the formula: HERS Index Score = (Reference Home Energy Consumption – Rated Home Energy Consumption) / Reference Home Energy Consumption * 100.
- Finally, calculate the HERS Index Score.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

Reference Home Energy Consumption (in BTUs) = 5000

Rated Home Energy Consumption (in BTUs) = 4000