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Guide · Sizing

40 vs 50 gallon water heater.Size by first-hour rating, not just gallons.

Pick between a 40 gallon water heater and a 50 gallon water heater the way DOE suggests.

40 gallon
50 gallon
First-hour rating

Background: Photo: Mcloward, Wikimedia Commons, CC BY-SA 4.0.

Quick answer: DOE says to size a tank by first-hour rating.^[1] Estimate your busiest hour of hot water use, then pick a tank whose rating meets it. A 40 gallon water heater suits many smaller homes. A 50 gallon water heater is the common step up.

Estimate your peak hour.

Think of your busiest hour, such as weekday mornings. Count showers, a load of laundry, and the dishwasher. Add the hot water each uses. That total is the first-hour rating to look for.^[1]

The rating is printed on the EnergyGuide label. Two 50 gallon tanks can have different ratings, so compare the label, not just the size.

When 40 gallon fits

One or two baths, light overlap, smaller households.

When 50 gallon fits

Larger families, back-to-back showers, a soaking tub.

Newly installed Rheem gas tank water heater with flue pipe and gas line, a common 40 or 50 gallon setup — Photo: Tim Evanson, Rheem gas tank water heater, newly installed. Wikimedia Commons, CC BY-SA 2.0.

Ready to swap? See water heater replacement in Layton, or compare with a tankless water heater.

Peak-hour calculator

Find the first-hour rating you need.

Enter how many times each use happens in your busiest hour. The gallons per use come from the U.S. Department of Energy's water heating fact sheet.^[1] DOE suggests a tank whose first-hour rating is within about 2 gallons of that peak.^[1]

Your total copies into the quote form.

Busiest hour of hot water

Shower 15 galBath 20 galShaving 2 galWashing hands and face 2 galShampoo 4 galHand dishwashing 2 galDishwasher load 14 galFood prep 5 galClothes washer load 32 gal

Peak hour demand

Get a sized quote

40 gallon vs 50 gallon side by side.

	40 gallon water heater	50 gallon water heater
Typical fit	Smaller households, lighter overlap	Larger households, back-to-back showers
What to compare	First-hour rating on the label^[1]	First-hour rating on the label^[1]
Space	Smaller footprint	Taller or wider, so measure the closet
Gas or electric	Both common	Both common, gas recovers faster
Hard water	Sediment still builds	Sediment still builds

Layton sizing notes.

Winter water comes in colder, so a tank works harder to reach the set point. That slows recovery in January.^[2]

Hard water matters too. Weber Basin says hardness can run 10 to 18 grains per gallon.^[3] Sediment takes up space at the bottom, so an old tank can act smaller than its label.

If your busiest hour is far past what a 50 gallon tank can deliver, look at a high-recovery tank or a tankless water heater in Layton.

FAQ

40 vs 50 gallon: FAQ

Is a 40 gallon water heater enough for a family of four?

Sometimes. Compare the first-hour rating to your busiest hour of use, as DOE suggests.^[1] If showers run back to back, a 50 gallon or a higher first-hour rating is safer.

Will a 50 gallon tank fit where my 40 gallon was?

Often, but not always. Taller or wider tanks may not fit a closet or the vent height. Measure first.

What is first-hour rating?

The amount of hot water a tank can deliver in an hour starting full. It is on the EnergyGuide label. DOE recommends sizing by it.^[1]

Should I go bigger than 50 gallons?

For large homes or big tubs, maybe. A tankless unit or a high-recovery tank are other options.

Not sure on size?

Tell us your household and current tank. Get a free sized quote.

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