Although there has been much interest in scaling laws for wireless networks, most work has focussed on characterizing throughput and delay in power-constrained networks. Energy-constrained networks have not received much attention. Previous work on energy-constrained networks was based on models that ignored interference. In this work energy-constrained networks are studied, taking interferences into account. The number of bits per unit energy is introduced, a quantity that measures performance of a wireless network in terms of energy consumption. Scaling laws for the number of bits per unit energy are analyzed on a extended random wireless network using the physical model. An upper bound is given and it is shown that it is achievable. The tradeoff between the number of bits per unit energy and the average bit delay is characterized. Finally, it is shown that there is no tension between the throughput and the number of bits per unit energy, i.e.\ they can be simultaneously optimized.