Residential water heating is linked to the primary source of waterborne disease outbreaks in the United States, and accounts for greater energy demand than the combined water/wastewater utility sector. Furthermore, home water heating is the second largest energy consumer in the home and thus represents an integral part of the water-energy nexus. To date, there has been little practical research that can guide decision-making by consumers, public health officials and regulators with regards to water heater selection and operation to minimize energy costs and the likelihood of waterborne disease. Scientific uncertainties associated with existing “green” advice have potentially created misguided policy with long-term negative repercussions. This review is aimed at defining the current state of knowledge related to hot water infrastructure and in highlighting current gaps in the research. While there are many sustainability claims of certain water heater types (i.e., hot water recirculation systems and instantaneous water heaters) these claims have not been substantiated in head-to-head testing of the interplay between water temperature, energy, microbial growth, and scaling, all measures that need to be better defined.