What Size Water Heater Do I Need for My Home?
admin • February 2, 2012

When installing a new water heater in your Lacey 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 tanks.

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 during the selection process. That will ensure you get the water heater that is right for you.

Plumber performing late-summer plumbing maintenance in an Olympia, Washington home.
By Paul Lightfoot August 18, 2026
Protect your Olympia home with late-summer plumbing maintenance tips for leaks, drains, water heaters, pressure, and outdoor plumbing.
Plumber installing new garbage disposal under kitchen sink during remodel in Olympia, Washington.
By Paul Lightfoot July 27, 2026
Planning a kitchen remodel? Learn the signs you need a new garbage disposal and the benefits of professional installation in Olympia, WA.
Concerned homeowner calling plumber after discovering signs of a water leak in Olympia, Washington.
By Paul Lightfoot June 30, 2026
Learn the warning signs of hidden plumbing leaks and how leak detection in Olympia, WA can help prevent water damage, mold growth, and costly repairs.
Kitchen garbage disposal grinding food scraps with running water to prevent clogs in Olympia, WA.
By Paul Lightfoot May 25, 2026
Learn what causes garbage disposal clogs in Olympia, WA, and when it's time to schedule professional garbage disposal repair services.
Plumber repairing blocked kitchen drain during leak detection service in Olympia Washington.
By Paul Lightfoot April 26, 2026
Learn what causes hidden water leaks in Olympia, WA homes. Schedule professional leak detection to prevent costly water damage and plumbing issues.
Homeowner on the phone with Brooks Plumbing showing a leaking plumbing system in Tumwater home.
By Paul Lightfoot March 17, 2026
Is your water bill higher than normal? Learn common causes like hidden leaks, water line damage, and water heater corrosion from a trusted Tumwater plumber.
Show More