Accuracy of home energy rating systems

We compared Home Energy Rating Systems (HERS) ratings and actual utility bi lling data for about 500 houses in four states. We found that HERS can, on average, predict annual energy cost accurately. However, on an individual h ouse basis the agreement between predicted energy cost and actual energy co st was often poor, especially for older houses. Discrepancies between predi cted and actual energy use have important implications for the true cost-ef fectiveness of HERS-recommended improvements. There was no clear relationsh ip between rating score and actual energy cost. Given these results, HERS p roviders 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 HERS' a bility to predict energy use. (C) 2000 Elsevier Science Ltd. All rights res erved.