What Temperature Should a Water Heater be Set at?


There are two opposing risks you need to consider before you decide on a temperature setting. If you set the temperature too low, you risk exposure to Legionella, the bacteria responsible for Legionnaires’ disease, but if you set the temperature too high, you risk scalding. A true dilemma, if there ever was.

Legionnaires’ disease is a serious illness associated with high death rates (up to 12%). Primary groups at risk are the elderly, the immunocompromised, and patients suffering from chronic respiratory illnesses. Although we do want people to protect themselves from scalding, we advise people to set the temperature high enough to prevent bacterial growth.

How To Check The Temperature Of Your Hot Water

Before you go about changing your temperature setting, you might want to know what it is currently set at. To find out what your current temperature setting is, you can just look at the temperature dial of your water heater. But if your water feels much colder than what the dial is suggesting, you can do a temperature check of your water.

There is no meter on your water heater you can look at to accurately determine the hot water temperature. You'll have to do it manually. You'll need a cup and a cooking thermometer. Before measuring, allow the hot water in the water heater to sit for at least an hour. Do not open any hot water faucets.

After the hour has passed, open the faucet nearest to the water heater. Let it run for a minute— this will heat the pipes and you will get a more accurate reading. After a minute, fill the cup and check the temperature with the thermometer.

The Best Water Heater Temperature Setting

Like a lot of decisions in life, this too depends on your situation, your needs, and your desires. Water heaters come with a default temperature setting of 140 degrees F. I interpret this as — water heater companies believe 140 degrees F is the optimal temperature for most people. Most people keep it that way and they are fine. However, you can consider different factors and change the setting suitable for your needs.

Energy Savings

Heating water requires energy. The hotter the water you want, the more energy you must spend. Therefore, more money. The Department of Energy recommends 120 degrees F for energy savings.

Bacterial Growth

120 degrees F is fine but it can allow bacterial growth. It might save you money but it might cause you some distress. This is not likely though. But if you are the type of person who always wants to be on the safe side, increase the temperature to 140 degrees F. There is a catch though. 140 degrees can cause scalding. A dilemma. What should you do?


It takes about two seconds for a child to receive third-degree burns from water that is 150 degrees F. If you have children, keep the temperature low. 140 can cause scalding as well but children are not idiots. They retract their hands. Just to be safe, keep the temperature setting at 130 degrees F. That way, you will be safe from bacteria as well.

Big Family

If you live alone, you won't run out of hot water even at 120 degrees F. But when you have 7 family members and everyone loves to bathe back to back in the morning, you can run out of hot water. Keeping the temperature setting at 140 degrees F can ensure that everybody gets a warm bath.

Big House

A big house has many faucets far away from the house.  The Farther the water has to travel, the more the heat will be lost, especially when the pipes aren't insulated. To compensate, you might have to keep the temperature at 140 degrees F.

I recommend a temperature of 130 degrees F. Hot enough to prevent bacterial growth. Safe enough for children. It can support big families. Water will remain warm enough to travel to the farthest faucet. And also save you some energy.

If you ask me for a range. It would be 120-140 degrees. Anywhere between that range, you will be fine. Still, you know enough to make your own decision.

For Your Dishwasher

Your dishwasher might not have a booster heater that heats your hot water even further. For proper cleaning, you might want to keep your temperature at 140 degrees F.

How To Adjust Water Heater Temperature

Depending upon the type, the method for changing your temperature setting is slightly different.

There are a few different ways of adjusting the temperature setting. Which method you have to follow depends on the type of water heater you have: gas, electric, or tankless. It is pretty easy to change the water heater temperature setting. Some types are slightly trickier than others.

The Water Heater Settings – Hot, A, B, C, Very Hot

Look at the temperature control knob or thermostat of your water heater. Gas or electric. If you are lucky, the temperature setting will be represented in numeric degrees—80, 90, 120 degrees F. Otherwise, different settings will be represented in ambiguous letters, words, and phrases—very hot, hot, A, B, C. Here's what those label means, regardless of your water heater type:

Hot (or a triangle) = 120°

A = 130°

B = 140°

C = 150°

Very Hot = 160°

Low (or Warm) = 80-90°

Vacation (or pilot) = Water is not heated but the pilot light is kept lit.

How To Change Gas Or Electric Water Heater Temperature Settings

Many gas water heaters are simple to change. You don't need any tools and you don't need to open anything. Simply rotate the knob to your desired setting. Most newer gas or electric water heaters however are a bit trickier.

  1. Turn off the electricity at the circuit breaker.
  2. Remove the access panel. If you have two, remove both of them. They might simply snap on or off. Or you might need a screwdriver.
  3. Peel back the insulation. You will find a thermostat.
  4. Rotate the thermostat with a screwdriver to your desired temperature setting. (Notation might be in numeric degrees—90, 100, 120 degrees F. Or in ambiguous letters, words, and phrases—A, B, C, hot.)
  5. If your water heater has two thermostats. The top one should be set slightly higher than the bottom.
  6. Put the insulation and the access panel back on.

For gas water heaters, you might need to relight the pilot light. Click here to learn how.

After you have changed the temperature setting, it will take a few hours for the water to reach that mark from room temperature. Wait for three hours. Check the temperature with the thermometer. Feel the water. If it feels too hot or too cold, adjust the temperature again.

If you're still not getting hot water, click here for solutions to common problems.