Ensuring reliability has and will continue to be a priority for electricity industry restructuring. Assessing the balance between public and private actions to ensure reliability should be guided in part by an understanding of the value of reliability to the nations' residential, commercial and industrial customers. Yet, there is no comprehensive body of information on this topic. This paper begins to address this information gap by analyzing studies conducted by electric utilities over the past 15 years to assess the value of electric service to their customers. Outage cost measurements prepared by 7 electric utilities through 20 studies are assembled and standardized into a national database of customer interruption costs. The database is used to describe trends in interruption costs, and regional (geographic) differences, differences in interruption costs by customer type. It can also be used to estimate customer damage functions.. Results from the study are intended to contribute to an improved understanding of the importance of electricity reliability to the nation.