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Water Heater Size: How to Choose

Published: February 8, 2019
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Various Water Heater Sizes

Sizing a water heater isn’t always an easy calculation. There are many factors involved and, depending on your needs, you might have several options available to you. But getting it wrong has consequences. Too small and you’ll have to settle for cold showers. Too large and you waste energy heating water that isn’t being used. We can help you decide what water heater size is best for you and your home.

Continue below to see the things you should consider when selecting your next water heater.

Quantity and Types of Fixtures

Start by listing the plumbing fixtures in your home that will be using hot water and their rated flow rates in gallons per minute (GPM). Faucets, shower heads and appliances like dishwashers all have different flow rates depending on the type and age. Shower heads have a range of 2-6 GPM, kitchen faucets flow at 2-4 GPM, and bathroom faucets average 1-3 GPM. However, keep in mind that older faucets have higher flow rates than modern ones with aerators. 

Duration of Usage

Once you establish the flow rate, multiply it by the length of time in minutes that you expect everyone to use the fixture at peak usage. Add them up to find the total gallons of water used at peak time. Make sure your water heater can support your long showers!

Woman in Cold Shower

Water Heater Recovery Time

Once hot water leaves your tank, cold water enters to replace it. This cold water mixes with the hot water and the mixture is then heated. The length of time this takes depends on the amount of cold water entering, the type of fuel, the heating capacity, the entering water temperature and the desired hot water temperature. The first hour rating (FHR) is a measurement of the amount of hot water, in gallons, that a tanked heater can provide in an hour. It takes into account your water heater size as well as the reheat time for incoming cold water. When selecting the correct water heater size, this is the number you should use to ensure that your peak demand is met.

Available Space for a Water Heater

Water Heater wall pipe

If you don’t have sufficient room for the heater and required clearances, you might be limited to a smaller heater. You might also have the option of a taller heater with a smaller footprint. A professional can assess and let you know your best options for a tight space. 

We have a lot of information when it comes to water heaters. Click HERE to see our other blog posts, or click HERE to learn more from our official website.

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