This paper proposes an estimation method of power system impedance based on powervariations caused by a distributed power generation system (DPGS) at the point of common coupling (PCC). The proposed algorithm is computationally simple and uses the voltagevariations at the point of common coupling (PCC) caused by the variations of the powerdelivered to utility network to derive the value of grid impedance. Accurate estimation of both resistive and inductive part of the impedance is obtained, as the results presented show.