What Size Tankless Water Heater Do I Need?

What Size Tankless Water Heater Do I Need

Many people are choosing to get a tankless water heater for their homes because of its many benefits. Aside from being highly energy efficient, it is also more cost-effective—especially when compared to older water heater models.

Have you thought of buying a tankless water heater for your property? If so, you should definitely get the sizing right before you buy. Not only will the wrong size be more difficult to manage and install, but it can also play havoc with your utility and water bills.

In this article, we guide you through the process of selecting the correctly sized tankless water heater for your home.

Step #1—Average Water Flow

Ideally, a bathtub would produce an average water flow of 4GPM (gallons per minute). A washing machine would have 2GPM of water flow, and a shower would have between 2.5 to 3GPM. Meanwhile, a kitchen sink and dishwasher would have 1.5GPM of average water flow.

Considering those numbers, you will need to figure out the number of devices that will be using the tankless water heater and the total flow rate of all of them combined. Simply add up the GPM and the result will be the overall flow rate you’ll need from the heater.

Step #2—Temperature Rise

What Size Tankless Water Heater Do I Need1During this step, you will need to identify the required temperature rise. You can do this by subtracting the incoming water temperature from the temperature that you want. If you don’t know the exact number, you can indicate the usual 50°F temperature. Most of the time, the water temperature needs to be around 105°F to 115°F. This means that a temperature rise of 55°F should be produced.

Step #3—Suggested Sizing

Selecting the most ideal size of tankless water heater depends entirely on you. In general, a home with one bathroom can function well with a unit that has roughly 4 to 5GPM. However, it will obviously not be the same case if you have a slightly bigger home. If you live in a house with two bathrooms, then you will probably need a tankless water heater that produces 6 to 8GPM. By having this, you can serve two to three different applications at the same time.

For homeowners who live in fairly large properties with a minimum of three bedrooms and corresponding bathrooms, one tankless water heater might not be enough. Instead, you will need to install several units in your house to sustain your water needs. More rooms mean more people, which also means a greater need for hot water. A single heater would not be enough in such case, and might even be overworked.

A word of advice: never choose a tankless water heater that’s too small for your space. Doing so will not save you money in the long run, as it will cost you even more in water bills because gallons of cold water can be wasted. Shooting low when selecting a tankless water heater is also not a good idea. It’s much better to shoot high and make a single time purchase upfront, and just let the unit pay for itself in energy bill savings over the coming years.

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