NOTICEThis report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. 1 In acknowledging individuals and organizations we do not mean to imply their endorsement of the research results. Our intention is simply to acknowledge their contributions and thank them.
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Executive SummaryThe National Renewable Energy Laboratory (NREL) conducted a series of assessments of the U.S. Department of Energy's (DOE) proposed Home Energy Scoring Tool (HEST). The primary objective of this work was to assess the accuracy of HEST as it was being developed and to provide information useful to DOE program managers and HEST development team at Lawrence Berkeley National Laboratory.NREL assessed the accuracy of HEST from the version used for the Home Energy Score pilot, released January 26, 2011, through the April 27, 2012 release. With the exception of Appendix A, Historical Progression of HEST Accuracy, this report reflects assessment of the April 27, 2012 release of HEST.
Comparison of Predicted Energy Uses to Measured Energy UsesPredictions of electricity and natural gas (NG) consumption were compared with weathernormalized utility billing data for a mixture of newer and older homes located in Oregon, Wisconsin, Minnesota, North Carolina, and Texas. 2 The 859 electricity comparisons and 500 NG comparisons yielded the following:• HEST underpredicted electricity use by a median of 1%.• HEST underpredicted NG use by a median of 10%.The primary objective of the Home Energy Score program is to issue a score to the homeowner. The Score ranges from 1 to 10, where a home scoring a 1 uses the most energy and a home scoring a 10 uses the least. For 52% of the homes in this sample, the predicted Home Energy Score is within ±1 point of a score calculated from measured energy use. 3
Comparison of Predicted Energy Uses to Predictions From Other ToolsSimilar comparisons were made between predictions from two other commonly used residential energy analysis software tools, REM/Rate and SIMPLE, and weather-normalized utility billing data for the same set of homes. The results of the comparisons are presented along with those from HEST in Table ES-1 and Table ES-2. HEST energy use predictions compare well with the other two energy analysis software tools....