120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting. Most experts agree that anything below 120 degrees creates a risk for bacteria to develop inside your water heater from stagnant water, such as legionella that causes Legionnaire's disease.
In the US, the maximum legal temperature for a water heater in a residential setting is 120 degrees. Most folks want to run at 125-130 degrees but be careful. The Federal law that stipulates the max temperature is because of folks, especially kids, getting burned by the water.
Although some manufacturers set water heater thermostats at 140ºF, most households usually only require them to be set at 120ºF, which also slows mineral buildup and corrosion in your water heater and pipes. Water heated at 140ºF also poses a safety hazard—scalding.
The maximum Department of Energy recommended water heater temperature setting you should never exceed is 140 degrees Fahrenheit. The lowest recommended setting should never be below 120 degrees Fahrenheit.
In general, this balance is best struck when your water heater is set to about 120°F (49°C). This temperature is hot enough to meet your daily needs, including a relaxing shower or a steaming hot cup of tea, while also being energy-efficient and safe.
If you have younger children in the house, you are always better to have your water heater set to 120 degrees to prevent scalding. If there are no kids in the home or your children are older, we would usually recommend turning the unit up to 130 or 140 degrees.
Understanding these settings can help when figuring out how to adjust the temp on water heater units. A typically represents around 130°F. B usually corresponds to 140°F. C indicates a temperature of about 150°F or higher.
Though the DOE says you can save money on hot water by lowering the maximum temperature of your water heater from 140° F to 120° F, we don't necessarily recommend it. That's because the lower temperature might invite opportunistic bacteria—including Legionella, associated with Legionnaires' disease—to proliferate.
To help prevent bacteria growth, the ASSE recommends keeping the water in your water heater tank at about 135 - 140 degrees Fahrenheit.
Raising the temperature setting on your water heater ultimately makes your hot water supply last longer. It will ensure everyone gets a hot shower, with plenty leftover to run your dishwasher and washing machine.
According to most dermatologists, the ideal shower temperature is anywhere between 98°F (37°C) and 104°F (40°C)—and no more than 105 °F (41°C). Rinsing under lukewarm water allows you to stay comfortable and maintain your body temperature while reaping all the benefits of both hot and cold showers.
We recommend always keeping the heater set between 110 and 120 degrees. In the summer, try setting your water heater temperature at the low end of this scale, placing it close to or at 110 degrees. In the winter, lean toward the high end of the range. During this season, 120 is a much more acceptable temperature.
According to Centers for Disease Control and Prevention (CDC), water temperatures ranging from 130 to 140 degrees Fahrenheit(°F) can eliminate most of the harmful bacteria. However, be warned that these high temperatures can also increase the risk of scalding.
Most homeowners should flush their water heaters every 6 months or so, but if you have extremely hard water, you may want to do it more often. Flushing your hot water heater could be necessary as often as every few months depending on the mineral content of your local water supply.
Adjust both thermostats to the same temperature setting. WARNING! Higher temperatures increase the risk of scalding. If you have increased the temperature setting above 120°F, install Thermostatic Mixing Valves at each point of use and set them to 120°F or lower.
Water Heater Temperature Recommendations
120 degrees Fahrenheit is the safety recommendation against scalding, but 140° is the common default setting.
Temperature Is Too High
The most obvious reason for a high water heater gas bill is if the temperature is set too high. According to experts, most homeowners should keep water heater temperatures between 120 and 140 degrees F.
Ideally you should heat your home to a temperature of at least 18 °C. This is particularly important if you have reduced mobility, are 65 or over, or have a health condition, such as heart or lung disease. Having room temperatures slightly over 18 °C could be good for your health.
The best temperature setting for a hot water heater is between 120 and 140 degrees. Below 120 degrees, bacteria can develop in the stagnant water sitting in the tank. Above 140 degrees, the water is so hot that you and your family members can be at risk for scalding in as little as two seconds.
Turning your water heater off completely when it's not in use can help you save a small amount of money each month on your energy bills, but the hassle of manually turning your unit off and on typically outweighs the benefits.
Faulty fixtures or leaking connections and pipes can go unnoticed at the water heater because it is not an appliance you see every day. The leaks can become significant and result in an increase in the water usage bill and your energy usage bill.
Ideal hot water temperature in winter
During the winter months, an optimal temperature for domestic hot water is around 55-60 °C.
The perfect temperature to set a water heater
And the default setting of 140 F (60 C) may be going away. Recent installation manuals for major residential water heater manufacturers actually call for a starting temperature of 120 F (49 C).
Generally, A means 120 degrees, B means 130 degrees, and C means 140 degrees.