This research aims to establish a system for technology selection in a public utility. Selecting the most appropriate Voice over Internet Protocol (VoIP) technology at the Electricity Generating Authority of Thailand (EGAT) is used as the case example. Seven EGAT experts participated in refining the criteria and selecting the alternatives using Analytic Hierarchy Process (AHP). The criteria are grouped using the affinity (K-J) diagram. 'Benefit' rather than 'low cost' criterion is given the highest importance. 'Intangible benefit' is given more importance than 'tangible benefit' sub-criterion. The selected technology turns out to be rather insensitive to changes in the importance of each main criterion.