A residential SOFC cogeneration system is composed of an electric power generating unit including SOFC cell stack which generates electricity and a hot water storage unit which recovers exhaust heat and stores hot water. The electric power generating unit is divided into a DC power module which generates DC power, a power conditioner which converts DC into AC, a controller which controls power generation, and other auxiliaries. The DC power module includes SOFC bundle, a reformer and a heat exchanger, and it generates hot water and reforms fuel while utilizing surplus heat and exhaust gas heat during power generation. It also stores hot water in a hot water storage tank of a hot water storage unit.