The energy supply method by distributed power supply is expected from the transportation loss of the power and a decrease in heat. The system using especially renewable energy and a fuel cell is excellent from the viewpoint of the environment. However the efficiency of the whole system depends on the amount of utilization of exhaust; heat. The system assumed in this paper installs a small fuel cell and a solar module in 12 buildings, connects each building with hot-water piping, and supplies fuel cell exhaust heat. The hot-water piping path that results in minimum heat release loss was investigated in the optimization analysis using a genetic algorithm. As a result, the optimal path of the hot-water piping considering the production of electricity of a solar module and ambient temperature was clarified.