As low powered, battery operated nodes are used in wireless sensor networks, conservation of energy at all levels of system design is very essential. In this paper, we focus on the efficient transmission of data over a noisy channel by selecting optimal energy efficient values for the physical layer parameters. We introduce an energy metric called “Effectually Received bit Energy” (ERE) which is the amount of energy spent in a successful transmission over a given channel. By minimizing this metric, we find the optimum hop distance and optimal transmit energy for different modulation schemes. The results which are obtained in this paper can be useful to the network designers for selecting the suitable hop distance, transmit energy and the modulation scheme that will help in maximizing the lifetime of the network. © 2014 Praise Worthy Prize S.r.l. – All rights reserved.