Provided is a network system including: a utility network including an energy generating unit; a home network consuming energy generated from the energy generating unit and including an energy consuming unit operating based on energy information including at least one energy price information; and a power adjusting device through which a current or a voltage supplied for an operation of the energy consuming unit is passed, wherein the power adjusting device reduces energy cost or an energy amount used by adjusting a voltage or current amount applied to the energy consuming unit based on the energy information.
