What Size Tank Water Heater Do I Need for my Denver Family?

September 26, 2018

Well, it depends. What kind of answer do you want?

If you only need a loose estimate (to get a sense of how much the unit will cost), use the general guidelines below:

  • For 1-2 people, you’d need a 30- to 40-gallon tank.
  • For 2-3 people, you’d need a 40- to 55-gallon tank.
  • For 3-4 people, you’d need a 50- to 65-gallon tank.
  • For 5+ people, you’d need a 60- to 85-gallon tank.

Need a much more accurate answer? Just use our step-by-step instructions below.

Want a professional to size and install your water heater for you?

For accurate tank water heater sizing, follow these steps…

Step 1: Determine your “peak hour demand”

Your peak hour demand is simply the amount of hot water you typically use in one busy hour.

The easiest way to determine your peak hour demand is to pick the hour you use the most hot water during the day. For example, most households’ peak hour demand is either 6am–7am or 7am–8am—when everyone is showering/preparing for the day.

Once you’ve determined which hour is your busiest (in terms of hot water usage), use the chart below to add up the maximum amount of gallons you’d use in that hour.

how to size water heater


Step 2: Choose a tank with a matching “first hour rating”

Once you’ve determined your peak hour demand, choose a water heater that has a matching or slightly higher first hour rating (you’ll probably see this listed as “FHR” on the tank).

What’s the FHR? It basically tells you how many gallons of hot water the tank can provide in one hour—starting with a full tank.

Every water heater has its FHR clearly labeled on the yellow EnergyGuide sticker. But if you’re shopping online for a tank, you can find the FHR listed under the “features” or “specifications” section of the tank’s product page (seen below).

water heater first hour rating

Image taken from an AO Smith tank water heater product page

Need help sizing your water heater? Ask a Denver plumber

Whether you’re looking to replace an old water heater or install one in a new house, we can help.

We’ll send over a licensed plumber to make sure your new water heater meets your hot water needs.

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