Experience with the Energy Rating Index (ERI) score as a building energy performance metric indicates that home geometry and operating assumptions play a significant role in resulting scores. All other things equal, as home size increases it becomes easier to achieve lower scores. The number of bedrooms and number of stories also impact scores. This presentation highlights the magnitude of the disparities caused by each of these factors in high performance zero energy ready homes. It also provides details on a set of Index Adjustment Factors that account for these impacts and significantly reduce disparities in the revised ERI calculation.