The ever-increasing complexity of applications covered by wireless sensor networks (WSNs) demands for increasing memory size, which in turn increases the power drain. It is well known that SRAM power consumption can be reduced by employing a banked structure, where unused banks are switched into the low leakage retention mode. In this work, we propose a new strategy for memory banking, taking advantage of the software properties of WSN, and achieving aggressive power savings. We present a detailed model for the energy saving for equally sized banks with two power management schemes: a best-oracle policy and a simple greedy policy. Thanks to our modeling, at design time the optimum number of banks can be estimated, and the design can reach huge energy savings. The memory content allocation and the power management problem were solved by an integer linear program formulation for two real wireless sensor network application (based on TinyOS and ContikiOS). Experimental results show an energy reduction of up to 77.4% for a partition overhead of 1%.