To provide a hybrid energy system which quickly responds at a low cost.

A hybrid energy system 10 supplies energy to a load such as an electric automobile. The energy system 10 comprises an energy storage apparatus 14 and a fuel cell system 16. If the storage of energy in the energy storage apparatus 14 is equal to or above prescribed storage, the energy storage apparatus 14 supplies all the energy that is supplied to a load 12. If the energy storage is below prescribed, the fuel cell system 16 supplies at least a part of the energy to the load 12. Unless an energy requirement of the load 12 exceeds an optimum energy output of the fuel cell system 16, the fuel cell system 16 supplies all the energy to the load 12.