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Selecting Tankless Water Heater Size

We make it easy to find the correct size tankless water heater for your home.

Tankless water heaters are rated differently than the traditional tank style water heaters. Instead of total gallon capacity, they are rated in gallons per minute, and their ability to heat the water at a given gallon per minute rate, called temperature rise. Correctly sizing a tankless water heater for your needs can be done in three simple steps.

1. Add up the total amount of hot water that you may be using at one time. For example, if you want to be able to run the shower and dishwasher at the same time, you would have a usage of 2.5 - 6.0 gallons per minute depending of the flow rate of your shower and dishwasher fixtures.

Average Flow Rates
Bathtub
Shower
Kitchen Sink
Laundry Sink
Dishwasher
Jacuzzi Tub
2.0 - 4.0 gpm
1.5 - 3.0 gpm
1.0 - 1.5 gpm
2.5 - 3.0 gpm
1.0 - 3.0 gpm
4.0 - 8.0 gpm

2. Find your average groundwater temperature on the map at the right. Subtract this from 120°F to find your needed temperature rise. (Note: 120°F is hot enough for most applications. However if hotter water is needed, a higher number can be substituted.)

3. Now that you know your maximum gallon per minute water usage, and required temperature rise, find the best fit for your application on our tankless water heater sizing chart below.

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