What Size Electric Tankless Water Heater Do I Need?

Installing a tankless water heater can help reduce energy costs and it is essential to select the appropriate size for your residence. The wrong size can lead to not enough hot water or a tankless water heater that works too hard, shortening its life and costing you more in the long run. So what size electric tankless water heater do you need? Read on to find out!

Not only will we cover how to calculate the right size of tankless water heater for your home, but we’ll also answer some FAQs about tankless sizes and costs. Get ready to take the plunge into energy-efficient hot water!

What Size Electric Tankless Water Heater Do I Need

What Does it Mean to Size a Tankless Water Heater?

Sizing a tankless water heater is an important step for homeowners who are looking to save money and energy by making the switch from a traditional tank-style water heater. It’s all about finding the right-sized appliance to meet your hot water needs.

When sizing a tankless unit, you’ll need to consider several factors such as peak hour (the time of day when your household will need the hottest water), demand (the number of hot water fixtures and appliances used during the peak hour), and temperature rise (how hot the cold water needs to be heated). To get 120°F hot water from a 55°F incoming temperature, you’ll require a 65°F rise.

It’s also important to factor in how many gallons per minute your kitchen faucet or shower head uses, how much hot water your washing machine or clothes washer requires, and how much hot water usage other household activities generate.

Knowing these details can help you determine which electric tankless unit or gas tankless model best fits your home’s needs.

Tankless Water Heater Sizing Chart

Tankless Water Heater Sizing Chart

How to Calculate the Right Size of a Tankless Water Heater

Calculating the right size of tankless water heater for your home does not have to be a complicated task. The first step is to determine the temperature rise, which is the difference between the winter groundwater temperature in your area and the preferred set temperature of your tankless water heater.

You can easily find this information by consulting a map of average winter groundwater temperatures or measuring it with a thermometer at its coldest time of year. Once you have determined the temperature rise, you will also need to consider other factors such as gallons of water, flow rate, kitchen faucets, and hot water faucets.

When all these factors are taken into account, you will be able to choose an electric tankless water heater that matches your needs and provides reliable hot water on demand.

Step 1: Flow Rate

Before you can decide on the size tankless water heater that you need, it’s important to consider the flow rate of your hot water outlets. The water flow rate is measured in GPM. To determine what size electric tankless water heater you need, you should first figure out your peak hot water demand.

This means adding together the flow rates of all the devices that will be running simultaneously, such as your washing machine, dishwasher, shower head, and any other fixtures or appliances that use hot water.

You can find this information by checking the product manuals for these items or by looking up their standard flow rates online. Once you have the total GPM for all your hot water outlets, you can use this information to properly size a tankless unit for your home.

Step 2: Temperature Rise

The second step in determining what size electric tankless water heater you need is to calculate your required temperature rise. The desired temperature is calculated by subtracting the feed water temperature from the output water temperature.

This calculation will give you a better idea of how much energy your tankless heater needs to produce hot water for your faucets and appliances.

To find out what temperature your feed water has, you have two options: use a thermometer to measure it or use our U.S. average groundwater temperature map as an estimate. Keep in mind that these are average temperatures, so if you live in an area with particularly cold winters or warm summers, these estimates may not be accurate and should be adjusted accordingly.

Step 3: Putting It All Together

Now that you know your hot water demand at peak hours as well as the required temperature rise, it’s time to put it all together and find the right tankless water heater for your needs. To do this, look for a tankless unit that meets or exceeds your peak hot water demand.

It’s important to remember that all manufacturers provide their own sizing charts with their products, so make sure to use this information when evaluating different models.


What Does GPM Mean?

GPM is an important factor to consider when shopping for a tankless water heater. It stands for “Gallons Per Minute” and it is the measurement used to determine how many gallons of water the tankless water heater can produce each minute. When selecting a tankless unit, it is essential to choose one with the appropriate GPM rating based on your hot water demand.

What Size Tankless Does a Family of 5 Need?

To ensure your household has enough hot water to meet its needs, you’ll need to select a tankless system that can provide at least 7 gallons of hot water per minute (GPM). To determine the right size electric tankless water heater for your family, you’ll need to consider factors such as climate, peak hour usage, and the number of fixtures and appliances running.

What Size Tankless Water Heater Do I Need to Replace a 50 Gallon Storage Tank?

If you’re looking to replace your 50-gallon storage tank water heater with a tankless unit, you’ll need to consider how much hot water demand you have. Tankless units heat water on demand, which means the size of the tankless unit determines how much hot water can be supplied at one time.

Which sizes last longer?

Gas tankless heaters usually last a lot longer than electric water heaters and can provide hot water for up to twenty years. Electric water heaters, on the other hand, tend to last only 7-10 years.

Where can I find the right model size?

Finding the right size electric tankless water heater can seem overwhelming, especially with all the choices available. Fortunately, you have a few options at your disposal. If convenience is your top priority, you can order an electric tankless water heater online.

What size tankless water heater can I install myself?

If you attempt to install a unit yourself you may end up with an ill-fitting heater that doesn’t provide enough hot water or could even be dangerous due to improper installation. For this reason, it’s highly recommended that you consult with a professional before attempting to install any type of tankless gas or electric heater.

What size tankless water heater is easier to maintain?

It depends on your hot water demand, the temperature rise necessary for your home’s hot water needs, and the average groundwater temperatures in your area. Smaller tankless units are easier to maintain because they have fewer elements that require cleaning or maintenance than larger models.

What are the prices for different tankless water heater sizes?

When it comes to prices for different tankless water heater sizes, gas-fired models range from around $180 for a small size to $2,000 for a large size. An average-sized model will typically cost around $1,000. Electric tankless heaters vary in price from $90 to $900.


The size of the electric tankless water heater you need depends on several factors, such as your hot water demand, washing machine, and kitchen faucets. You also need to consider the incoming water temperature and how many gallons of water you need per minute.

If you are looking for a gas tankless water heater, you should take into account the average groundwater temperatures in your area. On the other hand, if you are opting for an electric water heater, make sure to factor in your hot water usage and determine the temperature rise required.

Finally, don’t forget to adjust for moments of peak usage so that your tankless gas or electric water heaters can serve you at all times. With these considerations taken into account, you’ll be able to find the perfect size tankless water heater for your home and have hot showers whenever you want!