As there is a rapid growth both in the number of power consumers and also the limitations energy resources, it is clearly accepted that the old version of power grid must change into smart grid from head to toe. One of the most important advantages of smart grid which makes it much more exclusive rather than other typical systems is the two-way connectivity between the utility and the costumers. Taking energy efficiency programs for domestic consumers which are considered with the most important role in raising the rate of energy consumption of all, is accepted as an applicable techniques of demand-side management. In this thesis an identical frequency method control of the electrical motor of an air-conditioner (AC) system based on Fuzzy-PID controller is proposed in order to maximizing energy efficiency. Referring to the statistics which are published about the rate of energy consumption of AC systems would have the highest role in demand response and the two-way cooperation between the utility and costumers. To evaluate the results much more applicable, the proposed method is simulated with MATLAB software and the results have shown that the system have the great success.