This study, funded by the New York State Energy Research and Development Authority (NYSERDA) and performed by Performance Systems Development, identified the underlying causes for over-estimation of contractor-reported energy savings in the NYSERDA Home Performance with ENERGY STAR program for the years of 2007 to 2011 and assessed the potential impact on savings prediction accuracy of applying the ANSI/BPI-2400 standard for baseline energy model calibration to actual energy usage.