What Temperature Should a Tankless Water Heater Be Set At For Optimal Use?

Tankless water heaters don’t need to store hot water, so you’re not paying for wasted energy. But what temperature should a tankless water heater be set at?

A tankless water heater should be set between 120°F to 140°F. Ideally, 120°F is best, as it will prevent scalding.

Keep in mind that some people like their water very hot, while others prefer it lukewarm or even cold. If you tend toward one of those extremes, you may need to make adjustments based on what temperature is comfortable for you.

Understanding the right water temperature and setting it accordingly will help keep your tankless heater running efficiently and save money over time.

What Temperature Should a Tankless Water Heater Be Set At?

Studies show high temperatures can cause scalding, while low temperatures may result in getting cold water during use. The optimal temperature range for a tankless water heater is between 120 and 130°F. Check the manufacturer’s instructions for specific temperature settings for your unit.

If you have a suppressed immune system or a respiratory disease, it may be beneficial to keep the water heater at a higher temperature. In this case, a water heater temperature of 140°F is recommended. However, make sure to be careful if you have young children in the house.

Why is the Right Hot Water Heater Temperature Necessary?

When you’re ready to take a shower, the last thing you want to do is get scalded by boiling water. If your water heater temperature is too hot, that’s exactly what can happen. Find a balance between safety, energy efficiency, and comfort by setting the right temperature.

Water heaters can also be a breeding ground for dangerous bacteria such as Legionella when the temperature is too low. Legionella thrives in temperatures between 68 and 122°F and can cause serious illnesses like Legionnaires disease when ingested.

Symptoms of Legionnaires disease include coughing, fever, diarrhea, and even pneumonia, so it is essential to keep your water heater set within 120-130°F.

Additionally, water that is not hot enough may not clean and sanitize dishes or clothes properly, which can increase the risk of foodborne illnesses.

Important Things to Consider While Determining Your Water Heater Temperature

water heater maintenance temperature

By taking the time to analyze your household size, groundwater temperature, and energy costs, you can find the perfect temperature for your water heater.

Cost-saving is the first factor to consider. By adjusting the temperature of your water heater, you can save money on your energy bill. Depending on your heater and the amount of hot water you use, you can save up to $70-80 per year. This amount can add up over time and make up for the initial cost of a tankless water heater.

The second factor to consider is the groundwater temperature. This can vary depending on where you live and the time of year. If you live in a colder climate, you may need to increase the temperature of your water heater to make sure it’s hot enough. On the other hand, if you live in a warmer climate, you may need to decrease the temperature of your water heater to save energy.

Finally, you should consider the size of your household. If you have a larger family or many people living in the same house, you may need to increase the temperature of your water heater to ensure everyone can use hot water.

Do Water Heaters Break at Higher Temperatures?

You may need to go above 120°F to get the desired warmth during a cold climate. While it is possible to go higher, going above 130 degrees for long periods can prematurely damage the water heater due to pressure.

To prevent this issue, it is best to stick to a maximum temperature of 130 degrees Fahrenheit and be careful when using the water heater at a higher temperature.

How to Calculate Temperature Rise

The first step to calculating temperature rise is to figure out the incoming water temperature. This is the temperature of the water entering the heater, which may be lower than the desired heated water temperature.

The next step is to figure out the temperature you want from the heater. This is the temperature at which you would like the water to reach when exiting the heater. It will depend on your personal preference, but most households generally prefer water at around 120°F.

Once you have determined the incoming water temperature and the desired heated water temperature, you can calculate the temperature rise. Subtract the incoming water temperature from the desired heated water temperature to get the temperature rise. You must only select a unit that can provide the desired temperature rise.

What is the Drawback of Adjusting the Water Temperature to 140°F?

Adjusting the water temperature in a tankless water heater to 140°F can be a tempting way to get a faster, hotter shower or bath. However, this setting has a few drawbacks that make it a less-than-ideal choice.

First and foremost, setting your tankless unit to 140°F can be dangerous. 140°F is well above the recommended temperature of 120°F.

In addition to being dangerous, running your water heater at 140°F can also be expensive. This temperature requires more energy, which means a higher electricity bill. So it can be especially costly if you have multiple bathrooms that require hot water.


The optimal temperature setting for a tankless unit will vary depending on your needs and preferences. In general, a safe and comfortable temperature setting is between 120 and 130°F. Keeping the temperature between these two points can provide a hot water supply that is both safe and energy efficient.

Now that you know what temperature a tankless water heater should be set at, it will be easier to configure temperature settings.

With years of experience under his belt, Adam decided to put his water heater knowledge to work. By providing high-quality content and expert guides, Adam hopes to help anyone looking for expert water heater advice.