Hot Water Temperature Settings
Some dishwashers have models that do no pre-heat the water before the wash. For models like these, homeowners may want to set the temperature of their water heater to 140 degrees.
Households that may have elders or small children, should look to have a hot water temperature at 120 degrees. (Stock temperatures) usually leave the factory at 140 degrees. The skin of the elderly and the youth are more susceptible to third degree burns from water temperature above 140 degrees, according to babycenter.com
According to a recent study, for every 10 degrees you turn down your water heater temperature, you can save 3 to 5 percent on your monthly energy bill!
Those who live alone often have a lower water heater temperature because there is less demand for hot water & it saves money. Large households more than likely aim for a water temp much higher to accommodate the need for hot water for more people in the household.