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If you're tired of running out of hot water in the middle of a shower or dealing with a bulky traditional water heater, it might be time to consider switching to a tankless water heater. However, the big question is: What size tankless water heater do you need? Let's delve into the details and find out!

The Advantages of Tankless Water Heaters Before we delve into the sizing specifics, let's quickly recap the advantages of tankless water heaters. Unlike traditional water heaters that store hot water in a tank, tankless water heaters heat water on demand. This means they don't waste energy keeping a large tank of water hot, leading to significant energy savings and reduced utility bills. Additionally, tankless water heaters provide an endless supply of hot water, so you'll never run out during those long showers or when running multiple appliances simultaneously.

Factors to Consider when Sizing a Tankless Water Heater

Peak Demand:

The first and most critical factor to consider is your home's peak hot water demand. This is the maximum amount of hot water your household requires at any given moment. To calculate peak demand, consider the number of people living in your home, their typical hot water usage, and the number of hot water appliances used simultaneously. Keep Smiling Plumbing & Electric's expert technicians can assist you in this process, ensuring an accurate estimation.

Flow Rate:

Flow rate is measured in gallons per minute (GPM) and refers to the rate at which hot water flows from the heater to your faucets or appliances. Different fixtures and appliances have varying flow rates. For example, a shower typically requires 2-2.5 GPM, while a dishwasher may need 1-2 GPM. Knowing the total GPM for all fixtures and appliances in your home will help determine the appropriate tankless water heater capacity.

Temperature Rise:

Temperature rise is the difference between the incoming cold water temperature and the desired hot water temperature at the tap. Warmer climates will have lower temperature rises, while colder regions will need more heating. Keep Smiling Plumbing & Electric can help you determine the average groundwater temperature in your area, allowing us to calculate the required temperature rise for your tankless water heater.

Single Unit or Whole House:

Decide whether you want a single tankless water heater to supply hot water to specific appliances or a whole-house system that caters to all hot water demands simultaneously. Whole-house units generally require more power, so sizing is crucial to ensure optimal performance. Finding the Right Size Now that we have the essential factors in mind, it's time to find the right size tankless water heater for your home. Keep Smiling Plumbing & Electric recommends consulting with our experienced technicians to ensure accurate calculations and a seamless installation process. However, as a general guideline: For a small household (1-2 people), a tankless water heater with a flow rate of 4-6 GPM should suffice. Medium-sized homes (3-4 people) will likely need a unit with a flow rate of 6-8 GPM. Larger households (5 or more people) or those with higher hot water demands should consider a tankless water heater with a flow rate of 8 GPM or more.


Congratulations! You're now equipped with the knowledge to determine the appropriate size for your tankless water heater installation. Remember, correctly sizing your tankless water heater ensures you have a continuous supply of hot water without wasting energy or money. If you're still unsure or want expert assistance, don't hesitate to reach out to the friendly team at Keep Smiling Plumbing & Electric. We're here to make your transition to a tankless water heater as smooth and efficient as possible.