We estimated the benefits and costs of water fluoridation, in the New Zealand setting, for the Ministry of Health. This analysis was a large, complex assignment taking into account and integrating a large body of epidemiological evidence confirming the significant benefits of water fluoridation. We estimate the net savings from water fluoridation to be $1,401 million which is far and above what we would expect from most health settings. For children, these savings accrue to DHBs whilst adults save on largely private dental costs. Councils pay the cost of adding fluoride to council water supplies.