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Basnett Plumbing, Heating & AC Blog

Littleton Plumbing Queston: What Size Water Heater Do I Need for My Home?

When installing a new water heater in your Littleton home, it is important to get one that is the appropriate size. Of course, one that is too small will not handle the capacity you need, so you will be stuck with water that is not quite hot enough.

You may think to just buy one that you are sure can more than handle the capacity you need, but there are drawbacks to this strategy. A water heater that is “too big” will also draw more power, resulting in waste and unnecessarily high bills. Plus, it will cost more up front than you really need to spend.

The trick is to get a water heater that is the correct size for your needs. For a conventional water heater with a tank, the metric you will need to refer to is the unit’s first hour rating, or FHR. To determine the necessary FHR, you first need to determine during which hour of the day your home uses the most water. Typically, this is either first thing in the morning or later in the evening, when most people are bathing. Once you know this, determine what the water usage is during that hour based on average usage for each task. For example, let’s say a typical morning in your home consists of:

  • 3 showers (average of 12 gallons each)
  • 1 food preparation (5 gallons)
  • 1 hand dishwashing (4 gallons)

That’s about 45 gallons of hot water needed during that hour, so you need a unit with an FHR somewhere in that ballpark. The U.S. Department of Energy has a good worksheet to use for these measurements, which includes average usage rates for common household hot water tasks.

If you are looking at getting a tankless water heater system, the process is a little more complicated. The important figure to know in that situation is the maximum temperature increase possible for a particular flow rate. That means adding up the flow rates for all the various appliances you may use at once, then figuring out how much you need to increase the temperature.

If you find any of this confusing, consider a professional consultation with Basnett Plumbing & Heating during the selection process. That will ensure you get the water heater that is right for you.

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