Uninterrupted network operation in field sensing activities such as pollution monitoring is a big challenge, as the pollution sensors could be quite power hungry. One way to keep the network functioning is to recharge the nodes periodically via radio frequency energy transfer, which can be achieved by using a mobile robot that acts as an energy source and a data sink. Given a set of sensors deployed in a geographic area, a mobile robot is required to visit all the sensors in a way so as to avoid a node's energy drainage and its buffer overflow. Before optimum path planning strategies depending on a set of given sensing and physical environmental constraints, a critical task is to investigate the components of energy consumed by a node on different activities. To this end, this work does an extensive study on the energy consumptions with a few chosen pollution sensor examples. Based on the energy consumption and rectification parameters, the required recharging periodicity is derived. This analysis forms the basis of constrained mobility and path planning of the mobile robot. © 2013 IEEE.