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what size tankless water heater

Understanding What Size Tankless Water Heater Your Home Needs

One of the benefits of a tankless water heater is that it is much smaller than a traditional water heater — 80 percent smaller. Not only does a tankless water heater take up less space, but it is also more efficient. 

You can save water by opting to use a tankless water system. However, that is not all; a tankless water heater lasts a long time without maintenance. 

With all of these perks, it is obvious why a tankless water heater is a coveted system for homeowners. But how can you understand what size tankless water heater your home needs? 

Let’s take a look at the following to help you find out what size water heater you’ll need for your home.

What Size Tankless Water Heater Do I Need?: Size Factors

The size of a tankless water heater depends on several factors. One of the factors involved is the size of the home.

Another factor in determining the right tankless water heater size is the function of the heater. Other variables to consider are the location of the heater and any ventilation. When you know more about each factor, you can choose the perfect size for your home.

To determine the size of tankless water heater you need, you need to consider the gallons per minute. 

The gallons per minute (GPM) is the amount of hot water a tankless water heater can heat in one minute. A tankless water heater does not have a storage tank with a predetermined amount of water.

Instead, a tankless water heater gets water from a supply and lets it flow into your home. To determine the size of tankless water heater you need, you must consider how many people are in the household.

Family Members

More people in the home equals a bigger tankless water heater. But remember, bigger is not always better. 

You will only spend extra money on electricity or gas if you get a large tankless water heater. Try to match the needs of your household with your tankless water heater. The ideal tankless water heater possesses efficiency and cost-saving properties. 

A water specialist will help you make the best choice for your house.

Another consideration in determining the proper size of a tankless water heater is the number of appliances in your home. For example, there may come a time when someone is taking a shower while an appliance is on that also uses water. A tankless water heater heats a supply of water as the water enters your home. 

While a tankless water heater does not run out of hot water, it can be overwhelmed. If you overwhelm the tankless water heater, you use more hot water than supply. To avoid overwhelming a tankless water heater, you must consider the number of hot water appliances, such as your washing machine and dishwasher.  

The combination of appliance use and any shower or faucet use is complex. Consider these factors when determining the size of a tankless water heater. 

Average Tankless Water Heater

An average family of four can use a tankless water heater that provides seven gallons per minute. Where do professionals get the seven gallons of hot water number? The average family of four uses 6.5 gallons per minute. 

To be safe, a seven-gallon per minute estimate gives the family of four a half-gallon more than is necessary. It is better to err on the side of caution than to overwhelm the tankless water heater. To err on the side of caution, get a tank slightly larger than the needs of your family. 

A plumbing expert can help you make these determinations. Also, the size of the water heater you’re going to install might also affect the cost of tankless water heating.

Gallons Per Minute

The flow rate is the gallons of water per minute (GPM) that are supplied to the home. The water that comes into your home is groundwater. The temperature of groundwater varies around the United States. 

The reason for the temperature variance is the different climates across the United States. The groundwater temperature is important because it dictates how much the groundwater will need to be heated by the tankless water heater. 

That is why a tankless water heater sizing chart is helpful. It will help you determine the answer to the question: “How big of a tankless water heater do I need?” 

Colder groundwater needs to be heated more than warmer groundwater. A tankless water heater sizing chart combines the groundwater temperature of your area with the gallons per minute. You must combine the GPM flow number with the groundwater temperature to make inferences about tankless water heater size.


If a tankless water heater is something you need, knowing how to size a tankless water heater is necessary. 

American Home Water & Air has specially trained technicians that will help determine the size of the tankless water heater you’ll need before it’s installed. We’ll walk you through the entire process, including choosing which water heater works best for your needs. 

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