For reduction of Green house Gas emission, Polymer Electrolyte Membrane Fuel Cells (PEFC) ispromoted by the government in Japan as more efficient co-generation system(CGS). On this study forthe purpose of finding the efficient energy supply system with PEFC in the apartment house, first theauthor proposed PEFC Apartment House as more efficient system than the current one (boiler andelectric power), which consists of PEFC-CGS, thermal storage tanks, power network and managementsystem. Second, in order to develop the planning method of facilities with PEFC, the author has built upa database of PEFC performance by carrying out measurements at a residential house, and hasdeveloped an environmental and economical evaluation system. Third, for prediction of energyconservation and environmental effect of PEFC Apartment House, with the evaluation system theauthor has predicted annual primary energy consumption and carbon dioxide emission at a 30-unitapartment house in Tokyo. As a result, the author estimated about 14% reduction of annual primaryenergy comsumption and about 28% reduction of carbon dioxide emission.