In this paper, a smart metering system for domestic water flow meters is presented. The system comprises front-end readers that are attached to the legacy mechanical flow meters, and a cloudbased back-end system for data collection, monitoring and control. The paper focuses on the difficulties and challenges associated with the front-end segment, where tough requirements are imposed by utility companies. Careful firmware-hardware codesign is presented, with a main focus on the energy constraint. The processor selection and the architecture of the embedded firmware which achieves a system lifetime of 5 years yet allows daily communication is also demonstrated. Finally, the roadmap for mass production and deployment is considered.