In this paper, we study the improvement of power control in wireless ad hoc networks that use the DS-SS MAC layer protocol. We obtain the probability density function (PDF) and the cumulative density function (CDF) of the interference at a receiver node in a power-controlled network. We then use these PDF and CDF to compare the MAC layer performance of power-controlled and non-power-controlled networks. Packet success probability, expected hop length, expected energy spent per successful packet, and expected energy spent per meter per successful packet are the four performance metrics that we chose for the comparison. We show that the signal-strength power control does not increase the packing of the network nodes, but it does, however, reduce the power consumption by a factor between 3 and 4, for the same packet success probability.