Is there an optimum temperature setting for a tank type, gas or electric water heater? I have a large tank type heater connected to my boiler set at 110 degrees. I think this works very well but I have friends who think this is too low and have theirs set at 120 to 125 degrees. I think they are wrong, especially maintaining this temperature 24 hours per day, all year. What about people with cottages – how should they set the water heater? I think the water heaters come from the factory set at 120 degrees but I believe this is for planned obsolescence!
Simple answer – no – there is no optimum setting. I believe a setting of around 110 – 120 degrees is appropriate for safety and for energy conservation. You can’t be easily scalded by water at 110 degrees and the tank loses less heat to the environment. The down side to a lower temperature is you may not have that really hot shower depending on the piping in your home. Some dishwashers suggest a hotter water supply temperature for sanitation. Lower temperatures may also allow a buildup of powered detergent in dishwashers and clothes washers.
Scalding is a big safety issue. What does it take to produce a burn or scalding with hot water: at 120 degrees it takes more than 5 minutes; at 130 about 30 seconds; at 140 less than 5 seconds; at 150 about 1 ½ seconds; at 160 about ½ second. I think we need to keep the temperature down for kids and visitors.
In your case, you must have a coil heat exchanger inside a hot water home heating boiler that heats domestic hot water and stores it in a tank. With this type of system, you can set an actual temperature and there is some type of control to lower the boiler water temperature or blend in cold water to control the temperature. We don’t see a lot of these systems in Wisconsin but they work well.
For cottage owners, I suggest the 110-120 degree setting when the cottage is occupied. When the cottage is not used for few days or more, I would turn the water heater temperature setting to “vacation” or turn the power to an electric water heater off. I would also turn the water main off if leaving a home alone for a week or more.
I don’t think that water heater manufacturers plan for obsolesce with the 120 degree temperature setting. I think they use a setting that is safe and acceptable to most homeowners. If you want to make your water heater last a long time, drain sediment from the tank and change the anode rod periodically. The frequency depends on the quality of the water in your area. (The anode rod is a sacrificial, reactive metal that corrodes before the metal tank and saves the tank from corrosion.)