A major challenge in the two-tier femtocell networks-comprised of a central macrocell underlaid with femtocells is the efficient use of radio resources. Power optimization technique is one important component of radio resource management, since the deployment of femtocells may cause serious cross-tier interference and consume large amounts of energy. This paper presents an energy-efficient power control solution for interference-limited two-tier femtocell networks in the analytical setting of a game theoretic framework, where both circuit and transmission powers have been considered. First, we investigate a non-cooperative power control game for two-tier spectrum-sharing femtocell networks. In order to guarantee that cellular user can obtain its Signal-to-Interference-Pius-Noise Ratio (SINR) target, then we propose an algorithm that reduces transmission powers of the strongest femtocell interferers. According to simulation results, the proposed scheme can improve energy efficiency of femtocell networks and mitigate cross-tier interference significantly.