Advanced Metering Infrastructure (AMI), seen as foundation for overall grid modernization, is an integration of many technologies that provides an intelligent connection between consumers and system operators [ami 2008]. One of the biggest challenge that AMI faces is to scalable collect and manage a huge amount of data from a large number of customers. In our paper, we address this challenge by introducing a mixed peer-to-peer (P2P) and client-server communication architecture for AMI in which metering data is aggregated and processed distributedly at multiple levels and in a tree-like manner. Through analysis we show that the architecture is featured with load scalability, resiliency with failure and partly self-organization. The experi- ments performed in large scale French Grid5000 platform [G5k] shows the communication efficiency in the proposed architecture.