Laboratory and field studies have demonstrated that the use of window attachments such as cellular shades can provide significant savings by reducing energy consumed for heating and cooling in homes. The degree to which this measure saves energy, however, depends on a number of factors including the type of cellular shade, the structural and orientation characteristics of the home, the characteristics of the primary window on which it is attached, climate conditions, and operating schedules. This project, sponsored by Silicon Valley Power and the American Public Power Association's Demonstration of Energy and Efficiency Developments Program, examines the savings potential of cellular shades in 13 climate zones throughout California and the United States. The energy savings are modeled using EnergyPlus simulation software and include savings for three different prototype homes, two variations of window types and window area, and two different types of cellular shades. The model is validated using experimental data from the Pacific Northwest National Laboratory’s Lab Homes. The results from this study provide valuable input for utility incentive programs around the United States. The shading schedule implemented for this study is seasonal, more ideal than realistic, and meant to be simple enough to model in EnergyPlus. Shades are modeled as always down from April to September (simplified cooling season). They are modeled as up during the day (6:00 a.m. to 6:00 p.m.) and down at night (6:00 p.m. to 6:00 a.m.) from October to March (simplified heating season). The results demonstrate year-round heating and air-conditioning savings in all cases and climate zones examined. According to these models, double-cell shades provide nearly the same energy savings as triple-cell shades in most cases. Savings are most significant in existing homes with relatively high window-to-wall ratios. For these home types, energy savings associated with HVAC operation ranges from 6% to 41% depending on the climate zone.