Water Heater Optimum Set Temperature
I recently installed a hot water heater (gas 50 gallon), and did a bit of research to see what the temperature setpoint should be. There have been trends to lower temperatures to save energy, and prevent scalding. Some dishwashers heat the water so they can be less demanding than older models.
I was surprised in what I found. A significant issue is Legionnaires' Disease. Legionella can proliferate in hot water heaters if the temperature is not high enough. See the study at the link below. Short story is that they found contamination in 40% of electric hot water heaters, and none in gas water heaters. So this is a particular concern in electric heaters. They recommend a set point of 60 deg C (140 deg. F), and not the 49 deg C. (120 Deg. F), that is often recommended.
Here is a link that might be useful: Legionella in Hot Water Heaters