Advanced Metering Infrastructure (AMI) is an important element of the Smart Grid as it is expected to facilitate the transport of meter readings from meters to the utility provider and control information (potentially) in the other direction. One approach to realize AMI entails deploying concentrator devices in a neighbourhood. The meters would then associate with and subsequently communicate over single/multi-hop short range wireless links with the concentrator which in turn would forward the data to the data management systems. A key problem that arises in such networks is for the meter to decide which concentrator to associate with when multiple of these are available in the vicinity. This paper proposes a tree balancing algorithm called 'TREEB' which enables the smart meter nodes to assess the state of concentrators in the vicinity and use this information to decide which concentrator to join. TREEB has been realized as enhancements to the IETF RPL protocol without affecting backwards compatibility. It is practical to implement, operates in a distributed manner and helps to balance the networks of the different concentrators as shown by results obtained from its performance evaluation.