Accuracy of home energy rating systems

We compared Home Energy Rating Systems (HERS) ratings and actual utility billing data for about 500 houses in four states. We found that HERS can, on average, predict annual energy cost accurately. However, on an individual house basis the agreement between predicted energy cost and actual energy cost was often poor, especially for older houses. Discrepancies between predicted and actual energy use have important implications for the true cost-effectiveness of HERS-recommended improvements. There was no clear relationship between rating score and actual energy cost. Given these results, HERS providers need to give consumers more information about accuracy and how to interpret ratings. They should also take greater advantage of the thousands of ratings that have been conducted in order to assess and improve HERSʹ ability to predict energy use.