Power supply system

A power supply system having a cogeneration unit equipped with an internal combustion engine and a generator driven by the engine to generate power to be supplied to a power destination and hot water to be supplied to a hot water destination by heat exhausted from the engine, comprising:

• a natural energy generation unit that generates power with natural energy;
• a power supply unit that receives the power generated by the generator and the natural energy generation unit to supply the received power to the power destination;
• a connecting bus that electrically connects the cogeneration unit, the natural energy generation unit and the power supply unit;
• a voltage detector that detects voltage of the power flowing through the connecting bus;
• and
• an electric heater that heats the hot water by the power supplied through the connecting bus,
• wherein the power supply unit controls operation of the electric heater based on the detected connecting bus power voltage.