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What Size Tankless Water Heater Do I Need?


When it comes to maintaining a constant supply of hot water in your home, choosing the right tankless water heater size is crucial. Tankless water heaters, also known as “on-demand water heaters,” provide hot water only as it is needed. Unlike storage tank water heaters that maintain the temperature of a large volume of water, tankless units heat water directly without the use of a storage tank.

Are you currently asking yourself, “What size tankless water heater do I need?” We’re here to help. This blog will guide you through the process of determining what size tankless water heater you need for your home.

Understanding the Basics of Tankless Water Heaters

Before diving into how to size a tankless water heater, it’s important to understand the basic operation of tankless units. Unlike tank water heaters, which keep a large volume of water heated at all times, tankless heaters heat water directly as it flows through the unit. This on-demand heating ensures that you’re not paying to keep a tank of water hot when not in use, making tankless heaters a more energy-efficient choice.

Evaluating Your Hot Water Needs

When learning how to size a tankless water heater, you’ll first need to consider your peak hot water demand. This is the maximum amount of hot water your household will require at any given time. Think about your daily hot water usage — do you often have multiple showers running at the same time? Do you run the dishwasher while someone is in the shower? These simultaneous needs play a crucial role in determining the size of the tankless water heater you need.

Understanding Flow Rate and Temperature Rise

Two key factors in sizing a tankless water heater are the flow rate and the required temperature rise. The flow rate, measured in gallons per minute (GPM), refers to the amount of water that can be heated at any given time. Different appliances and fixtures have different flow rates — for example, a shower head may have a flow rate of 2.5 GPM, while a clothes washer may have a higher rate.

Temperature rise is the difference between the incoming water temperature and your desired output temperature. If your incoming water is relatively cold, your tankless water heater will need to work harder to achieve the desired temperature, requiring a higher capacity unit.

What Size Tankless Water Heater Do You Need?

To calculate the size of the tankless water heater you need, start by listing all the devices in your home that use hot water. Note their flow rates and add them up to get your total flow rate. Then, determine the temperature rise needed based on your groundwater temperature and desired hot water temperature. These two factors — total flow rate and required temperature rise — will guide you in choosing the right size tankless water heater.

Considerations for Households With High Demand

For households with high hot water demand, such as those with multiple bathrooms or large families, a larger tankless unit or even multiple tankless units might be necessary. It’s also important to consider the maximum flow rate a heater can provide at your required temperature rise; different models have different capabilities.

Why Choosing the Right Size Matters

Selecting the right size tankless water heater is vital for efficiency and comfort. A unit that’s too small will run out of hot water during peak times, while a unit that’s too large will be more expensive and less energy efficient than necessary. It’s about finding the balance between meeting your hot water needs and not overspending on an oversized unit.

Trusting the Professionals for Installation

It can be helpful for homeowners to learn how to size a tankless water heater. However, it’s always a good idea to consult a professional. An expert in the field will make sure that you install the right equipment for your household’s needs.

Apollo Heating, Cooling, and Plumbing, with our expert plumbers in Kent, OH, is your go-to for reliable and efficient tankless water heater installation. Our team can ensure that your unit is installed correctly and efficiently, providing you with endless hot water and peace of mind.

Ready for Endless Hot Water? Contact Us Today!

So, what size tankless water heater do you need? As you can see, the answer to this question will vary from household to household. There are several factors you will need to consider to find the right solution for your specific needs.
Now that you know how to size a tankless water heater, why wait? If you’re ready to enjoy the benefits of a tankless water heater, don’t hesitate to reach out to Apollo Heating, Cooling, and Plumbing. We can help you determine the appropriate size for your home and provide a hassle-free installation. Schedule your tankless water heater installment in Northeast Ohio today and enjoy the comfort of endless hot water!

A tankless water heater installed on the exterior of a house.