A direct comparison of Site Energy Use Intensity (EUI) between two properties is not an accurate way to compare performance. This comparison fails to account for differences in fuel type, weather, or operating characteristics (such as Number of Workers and Operating Hours).
The ENERGY STAR Score is a better metric for comparison because it accounts for:
- Fuel type through the use of Source energy rather than Site energy. For an explanation, see our webpage on the difference between source and site energy.
- Differences in weather through the process of weather normalization. For example: Property A had an extra cold winter, Property B had a mild winter.
- Differences in operating characteristics (example: one property has 1 computer per employee, and the other has 2 computers per employee).
If you don't have an ENERGY STAR Score, EPA recommends you use Source EUI as the comparison metric because it adjusts for:
- Fuel type through the use of Source energy rather than Site energy. For an explanation, see our webpage on the difference between source and site energy.
- Differences in weather through the process of weather normalization (example: Property A had an extra cold winter, Property B had a mild winter).