PURPOSE: To rationally perform cooling and heating and emergency power generation with the use of a common device by driving an engine using stationary supply gas fuel to perform cooling and heating at normal time and driving the engine using the maintenance fuel, such as petroleum that is stored to perform power generation at emergency.

CONSTITUTION: A fuel tank 3 which stores the maintenance fuel such as petroleum and a city gas piping facilities 2 are connected to the engine fuel supply system (f) of a main system (A) through a fuel changeover devicd 4. An air conditioner 6 and a power generator 7 are connected to the rotary output system (e) of an engine 1 through a power changeover device 5 so as to selectively be switched and the engine 1 is started by a starter device 9 which is connected to a power supply 10. Beside, the starter device 9 is automatically operated by a power off detector 11 at power failure and emergency power generation is performed by switching the changeover device 5 into the power generator 7 side. The exhaust system (g) of the engine is connected to an auxiliary system (B) containing a heat exchanger 12 and a cooling water circulating system (r) is connected to an auxiliary system (C) containing a warm reservoir 17.