Thermochromic windows are a new type of fenestration that automatically change the solar transmission by a special thin film laminated between two panes of glass.This special film can self-darken and its darkness is governed by the direct solar radiation impacting the glazing and interstitial temperature between the panes. An empirical demonstration project was conducted to assess the year-round building energy performance of a thermochromic window model compared to a highperformance low-e dark tinted window model in a light commercial building environment that uses automatic dimming control under central Iowa weather conditions. After discounting the average annual normalization error of 5.6% between the two demonstration systems, results show that on a yearly average, the thermochromic windows can save approximately 4% total building electricity compared to the high-performance low-e dark tinted windows under test. Lighting energy savings is significant due to the increased amount of visible light thermochromic windows allow because of the self-darkening tint. However, this work is focused on assessing energy savings of the thermochromic windows without considering glare and solar protection. Energy savings comparison with shadingoptions is needed for future research.