A fuel cell unit system is disclosed, which is provided in a multi-home energy supplying system, wherein the multi-home energy supplying system includes the plurality of fuel cell unit system provided to respective houses, and one common-use reforming unit to supply hydrogen to the plurality of fuel cell unit system, the fuel cell unit systems (40) comprising a stack unit (300) which generates electricity by an electrochemical reaction between supplied air and the hydrogen supplied from the common-use reforming unit (10); an air supplying unit (100) which supplies the air to the stack unit; an integral heat exchange unit (500) which cools the stack unit by recovering the heat from the stack unit, and stores the recovered heat; a hot-water supplying unit (200) which receives the heat stored in the integral heat exchange unit, and provides heat and hot water; an auxiliary heat supplying unit (400) which generates the heat by receiving the air supplied from the air supplying unit, and the hydrogen directly supplied from the common-use reforming unit or discharged from the stack unit after the electrochemical reaction, and supplies the generated heat to the hot-water supplying unit; and an electric output unit (600) which converts the electricity generated in the stack unit into a utility power, and supplies the produced utility power to the respective houses.