The impacts of electric service interruption to customers depend on customer and interruption characteristics. Customer characteristics include demographic aspects (residential type, and number of household members) and power supply types whereas interruption characteristics include frequency, duration, time, and day of interruption. Accordingly evaluation of these customer interruption costs is very complicated and subjective. For residential customers, customer survey method seems most appropriate because interruption impact to residential customers is intangible. In other. words, the value of housework or lost leisure due to interruption is individual. Accordingly, this paper selected the customer survey method to assess the interruption costs for residential customers.