Tankless Water Heater Temperature

rinnai tankless water heater temperature display

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A tankless water heater provides many benefits over the traditional storage-based system. Instead of heating water in advance and then store it for later use, the instant system only heats the water on demand. Besides costs and energy savings, tankless water heaters are easy to install and maintain. Although they provide energy and water savings, you can optimize the temperature to improve safety and reduce your bills further. In particular, lowering the temperature will save energy and reduce water usage without sacrificing comfort.

Why change the water heater temperature

While you may need certain temperatures for some applications, the heat may be inadequate or uncomfortable for others. Usually, tankless water heaters have a default temperature setting of 140 degrees Fahrenheit. However, this may be too hot for some users and especially the children and elderly. Even for young and middle-aged people, the hot water may burn or scald them.

Tankless water heater LED panel – Image Ecotouch

Usually, the safe and comfortable temperature is 120 o F or 50 o C but you can still set it to a lower value depending on your preference. Some heaters incorporate anti-scald devices or thermostatic mix valves that regulate the temperatures and ensure that it reaches the point of use, such as the showerhead or sink at a constant and safe 120 o F or 50 o C. However, these will only improve safety but do not provide much energy savings since they will cool the water near the outlet.

When a unit serves many applications such as showering, dishwashing, laundry, and more, you may need to install it in the most appropriate place and then run pipes to the application area. As the water flows through the piping, it will lose some heat to the surrounding and reach the sink or showerhead at a lower temperature. 

In particular, using uninsulated metal pipes over long distances will lead to significant losses. In such cases, you may consider adjusting to a higher temperature to compensate for the losses. However, this will result in more energy use and bills.

That said, although you have the liberty to set your temperature at the maximum figure, you may need to consider other issues such as safety, especially if other people are using the same shower or water to do dishes and other activities. You also need to note that the higher the temperature, the higher the energy you require for heating your water.

Advantages of low-temperature settings on a tankless water heater

Benefits of adjusting the temperature of a tankless water heater include improving safety by preventing scalds and burns and reducing your energy and water bills. 

Saving energy

If you set your temperature too high, you will require more energy to heat the water. And this means higher energy bills at the end of the month. In a typical setting, reducing the temperatures by 10 degrees results in 5% energy bill savings, and you can realize 10% savings if you reduce by 20 degrees. However, this may vary depending on the heater model and efficiency. Besides the savings, using less energy reduces environmental degradation.

Improved safety 

The default temperature setting for a new tankless water heater is usually 140 o F or 60 o C. Generally, showering with such hot water can burn or scald you seriously. In particular, the temperature is too high for the elderly since they may take time to sense the excess heat. Similarly, children are at risk due to their delicate skins. In either case, the hot water may lead to scalding or burns. 

Saving water

If you heat to higher and dangerous or uncomfortable temperatures, you need to mix with more cold water to make it comfortable and reduce the risk of burns. As such, you end up using more water, unlike if you had just heated it to a lower and more comfortable temperature.

Checking your hot water temperature

If you do not know your current water temperature setting of the tankless water heater, check the LCD, if any, or at the dial position for some models. Alternatively, use a thermometer to manually check the water temperature at the outlet of the shower, sink, or other application areas. First, turn on the water heater, let it run for a few minutes, and then take the reading.

While you can rely on the tankless water heater thermostat to maintain the temperature at your desired value, you can check it manually at the outlet. Losses and other factors may cause temperature changes between the heater and point of use. You should then adjust the settings to compensate for the losses and ensure that you achieve the desired output that is comfortable and cost-effective.

How to adjust the tankless electric water heater temperature

Most tankless water heaters provide a flexible temperature range to suit different applications and preferences. For example, if you want to shower with scalding hot water, you can set your temperature at the maximum setting, which is about 140 o or 150 o F for most units. However, for most people, a 120 o F or 50 o C setting provides a comfortable and safe temperature for showering. 

In practice, tankless water heating systems have adjustable temperature settings. However, the accuracy and method of adjusting may vary from one model to the other. As such, you need to establish your system and how to change the settings, usually available from the user’s manual.

For tankless water heaters with an LED panel and control, adjust the temperature while checking the water to ensure that you get the right setting. For some models, you may need to use dial control. Once you set a temperature, an inbuilt thermostat monitors the water as it gets hot. Upon reaching the set temperature, the thermostat cuts off the power to the heating element. It then continues monitoring the water and powering the heating element, on and off, to maintain the water at the set temperature.

Adjusting temperature on tankless water heater -Image:Noritz

As mentioned earlier, you may consider using a thermometer to ensure that your water is at the right temperature at the point of use. Alternatively, feel the water on your skin and, if possible, ask all the other users to check so that you can adjust the temperature to a safe setting for everyone.

In a home where one tankless electric water heater serves multiple applications such as dishwashing, laundry, and shower, you will set the temperature once. However, if you have different tankless heaters around the house, each for its specific application, you need to adjust the temperature individually to suit the application.

Thermostatic mixing valve

Another approach to ensure that the water reaches the shower or other application area at the desired temperature is to use a thermostatic mixing valve. It automatically mixes the right amount of hot and cold water to provide the set temperature while responding to fluctuation in the pressure or other factors. The add-on device, installed near the hot water outlet, controls temperature hence improving safety and comfort.

Remote temperature control

With most modern tankless water heaters, you can add digital technologies that would allow you to control them remotely. For these models, you can connect them to the internet using Wi-Fi or other communication technologies. Adding connectivity enables you to adjust the water temperature using your phone or tablet. It also gives you the ability to monitor the usage of hot water, electricity, or gas remotely. For example, the solution allows you to turn off your heater remotely from anywhere, even when you are not at home.

Temperature control via smart phone – Image: Noritz

All you need is to purchase and install the wireless digital control kit. However, this will also require an internet connection to enable you to control the heater remotely from your tablet, smartphone, or other connected devices. 


Although a tankless comes with a considerable temperature range, the default setting of 140o F may be too hot and uncomfortable for most users. At this temperature, there are high risks of burns and especially for children and the elderly. As such, you should consider using a lower setting. In most cases, a temperature of 120 o F is safe and comfortable for everyone, not forgetting that it helps you save on energy and water bills and the environment.

Luckily, most of the tankless water heaters in the market provide an easy control system that allows you to adjust ot customize the water temperature according to your needs.