The Occupational Safety and Health Administration recommends setting residential water heaters at a temperature of 140 degrees Fahrenheit. The lowest safe temperature allowed for most homes is 120 F.
A water heater set between 130 F and 140 F allows the water temperature at the faucet to stay above 120 F, which is the safe minimum. Lowering the temperature on a residential water heater from 140 F to 130 F is an effective way to save on yearly energy costs, reduce the risk of scalding and prevent corrosion in the hot-water system. However, temperatures below 140 F slightly increase the potential growth of harmful bacteria and the development of Legionnaires’ disease, which can be deadly.