The present invention provides an adjustable volume family energy system utilized by step energy, the invention includes a compressor, a hot water heat exchanger, a four-way reversing valve, an outdoor wind cooling pipe coil, a first check valve, a second check valve, a first electronic expansion valve, a second electronic expansion valve, an air conditioning hot and cold heat exchanger, a gas-liquid separator, a water side electric three-way control way, a first solenoid valve, a second solenoid valve, a first water pump, a second water pump. These parts form a refrigerant loop, a domestic hot-cold water loop, realize refrigerating and hot water supplying, single refrigerating, single hot water supplying, single warm supplying, warm supplying and hot water supplying five modes. The control part of the refrigerant loop only has four-way reversing valve and electronic expansion valve in traditional air conditioning system, does not exist refrigerant potential safety hazard. The functionof each system is mainly realized by switch and adjustment of the water side two solenoid valves and electric three-way control way, has a simple control, credible security.