Starting with the 2012 version, the Scoring Tool uses an expanded scoring method which maps a home to its local weather station and a unique 10 point scale for that climate location.
Under the initial Home Energy Score program design for pilot tests, each of 19 geographic zones across the United States had a corresponding 10 point scale with source energy thresholds defined for each point on the scale. However, analysis showed that weather differences within each of the 19 zones are significant enough to skew scoring results. In fact, the scores of identical homes – with different weather but within one geographic zone - could vary by several points. As a result, the Department of Energy recognized the need to generate a larger set of 10 point scales for more than 240 different weather stations across the U.S.
In the final stages of testing the Scoring Tool, in an effort to more accurately account for climate differences the final version of the Scoring Tool was used to estimate the source energy use for a wide range of homes in each of the 240+ weather station locations (See table example below). The DOE then established energy values for the 10 point scale in each location based on the following guidelines and objectives:
In order to help homeowners to understand how a home compared to other comparably sized homes, LBNL used the RECS 2005 regression methodology, developed by Oak Ridge National Laboratory (MacDonald, 2009) for the EPA Home Energy Yardstick program, to calculate a reference pointer for small and large homes on the 10-point scoring scale. The analysis method facilitated the creation of two BTU based reference lookups, one with 1500 ft2 as the baseline home and the other with a 3000 ft2 home. These two reference lookups are used to position the “Top 20% of similarly sized homes score here or better” pointer that appears on all Home Energy Score labels. The RECS national average single-family home size is approximately 2200 ft2, so the Home Energy Score method uses the 1500 scoring bins when rating homes below the national average and the 3000 scoring bins for homes above.
With the above methodology, the Home Energy Score label is able to convey enough information about the home’s absolute energy consumption and its relative performance against homes of a comparable size.