Power control is often invoked in mobile ad hoc networks to achieve one of two popular goals: i) increasing network throughput by mitigating the effects of mutual interference of nodes or; ii) ensuring minimal power consumption. This paper proposes a new adaptive power control algorithm for ad hoc networks to save energy while maintaining a similar throughput as that achieved by the IEEE802.11 MAC protocol. The contributions of this proposed scheme are two fold. First, we define and invoke the concept of MAC packet delivery curve to guide the power control algorithm in the adaptation decision under different possible scenarios. In particular when choosing among different service profiles the packet curve can tell which is better in the long term. Secondly, the power control algorithm takes into consideration the short term correlations between transmit powers of RTS/CTS frames and those of DATA/ACKs frames, to ensure robustness.