An electricity generating and air conditioning system with a water heater. The system includes an engine, a generator connected to an output shaft of the engine to generate electricity, a heat pump type air conditioner, which uses the electricity generated from the generator, and comprises a compressor, a directional valve, an outdoor heat exchanger, an expansion device, and an indoor heat exchanger, a water-heating heat exchanger to heat water, and a waste heat recovering means to supply waste heat of the engine to the heat pump type air conditioner or to the water-heating heat exchanger, so that the system exhibits a high energy efficiency.