The systems configuration and operation plan of a fuel cell energy network using the micro-grid of the power using a solid polymer membrane-type fuel cell and the hot-water piping network to which exhaust heat is conveyed are considered. In this study, a computer program that optimizes the equipment arrangement of each building linked to a fuel cell network and the path of the hot-water piping network for supplying the exhaust heat of fuel cells and reformers to each house under the cost minimization objective was developed. As a result of analyzing the fuel cell network constructed in four to nine houses using the energy demand pattern of the average house of Sapporo, which is a cold, snow-covered city, compared with the system that is not optimized, it clearly showed lower equipment and installation costs. As a result of using and analyzing the energy demand pattern of the house in Sapporo, and outside temperature data in February, there will be 18%-25% cost reduction by optimization. Having optimized and planned the path of hot-water piping and arrangement of equipment so that the heat release of a hot-water piping network decreases is a reason for the cost reduction result. Furthermore, by this study, the capacity of a heat storage tank, and the arrangement planning of boilers and each capacity, and the quantity of flow of the hot-water circulating pump were investigated, and the operation plan of each piece of equipment was considered. (c) 2006 Elsevier Ltd. All rights reserved.