This paper, the fuzzy logic is proposed to evaluate the outage cost of large electronic industries in Thailand. Two selected parameters input in the fuzzy logic model are the peak demand and outage frequency. The simulation results of 105 large electronic industries with peak demand between 1 MW to 9 MW show that the outage cost is 35,067-938,267 Baht/event. Furthermore, the outage cost is used to assess the economic value of new 115/22 kV substation construction. In this article, the Air Insulated Substation (AIS) and Gas Insulated Substation (GIS) are used to demonstrate the economic value assessment of new substation in term of Return on Investment (ROI) and Internal Rate of Return (IRR). The results show that ROI and IRR of the AIS are better than ROI and IRR of the GIS both considering and without considering the outage cost.