The ever-increasing complexity of applications of wireless sensor networks (WSNs) demands for increasing memory size and larger memory size increases the power drain. It is well known that SRAM memory 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 detailed model for the energy saving for equally sized banks with two power management schemes: a best-oracle policy and a simple greedy policy. The model gives valuable insight into the particular factors (coming from the application, the technology and design decisions) critical for reaching the maximum achievable energy saving. Thanks to our modeling, at design time the optimum number of banks can be estimated to reach more aggressive energy savings. The memory content allocation and the power management problem were solved by an integer linear program formulation for a real wireless sensor network application. Experimental results show an energy reduction of 79.2% for a partition overhead of 1%.