: Please tell me the upper and lower optimum settings for a dual element electric hot water heaterNot sure what you mean by optimal. Do you mean what temperature do you want your hot water? Or do you mean should you set your thermostats to different temperatures for optimal performance? I would set the upper and lower thermostats to the same temp, a temperature that provides enough hot water but not so high as to cause scalding if you have small children or elederly people in your home. Scalding info and water heater info on my website.