The deployment of smart metering provides an immense amount of data for power grid operators and energy providers. By using this data, a more efficient and flexible power grid can be realized. However, this data also raises privacy concerns since it contains very sensitive information about customers. In this paper, we present Elderberry, a peer-to-peer protocol that enables near real-time smart metering while preserving the customer’s privacy. By forming small groups of cooperating smart meters, their consumption traces are anonymized before being aggregated and sent to the grid operator. Through aggregation, Elderberry realizes efficient monitoring of large numbers of smart meters. It reaches this goal without computationally complex cryptography and adds only little communication overhead.