40 vs 50 Gallon Water Heater: Which Size Do You Need?
Short answer. One or two people with one bathroom are fine on 40 gallons. Three or four people, two bathrooms, or a soaking tub should go 50. The tiebreaker is first hour rating, not the number on the label.
- Sizing based on peak hour demand, not household guesswork
- First hour rating explained in plain terms
- Free sizing advice before you buy anything
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What it is
Water heater tank capacity Water heater tank capacity, most commonly sold as 40-gallon or 50-gallon models, is the amount of hot water a storage tank water heater holds ready for use before it needs to reheat incoming cold water.
Denver's high altitude and colder incoming groundwater mean a tank has to work harder to hit target temperature, so sizing the tank correctly for the household keeps hot water from running out mid-shower.
First hour rating matters more than tank volume
First hour rating is how much hot water the unit can deliver in one busy hour, combining what is stored with how fast it reheats. A well-recovering 40 gallon gas unit can out-deliver a slow 50 gallon electric one. Compare that number across units, then check the tank size.
- Undersized means cold showers on busy mornings
- Oversized means paying to keep water hot you never use
- Gas recovers faster than electric at the same capacity
- A tub filler or rain head changes the math on its own
Go up to 50 gallons if
- Three or more people share the morning routine
- You have two or more full bathrooms
- There is a soaking tub or a large-volume shower head
- Laundry and showers overlap regularly
- You already run out with a 40 gallon tank
How we size a tank
- Count of people and their peak hour, usually the morning block
- Fixture flow rates, since a rain head can double a shower's draw
- Gas versus electric recovery rate for the same capacity
- Physical space, since a 50 gallon tank is taller and wider than a 40
- Venting and gas capacity check before committing to a bigger burner
- A recommendation you can take to any installer
What to expect and how the work gets done
- 1
Tell us the household
People, bathrooms, tub type, and when everyone showers.
- 2
Check the space
Closet height, width, and clearance decide what physically fits.
- 3
Compare first hour ratings
We line up two or three real units, not just tank sizes.
- 4
Install or advise
Take the recommendation and run, or have us do the swap.
If sizing is the question, tankless changes it entirely. See the full tank versus tankless table on our Denver water heaters hub.
Compare tank and tankless water heatersCredentials, reviews, and company proof
- Colorado Master PlumberFixture and appliance work is permitted and code-compliant, not handyman work.
- Plumbing Contractor license 2110Licensed to pull permits and pass inspection on gas, water, and drain work.
- Serving Denver since 2006Two decades of Front Range water chemistry, altitude, and inspection practice.
Ready when you are
Tell us what is happening and your Denver neighborhood. We will route it fast.
Cost difference between 40 and 50 gallons
The unit gap is modest. The install gap depends on whether the bigger tank still fits and still vents.
Need help right now? 24/7 emergency plumbing service. Planning a larger repair? See financing options.
- Unit price difference between capacities
- Whether the taller tank clears the existing closet or ceiling
- Gas line or flue changes for a larger burner
- Electrical circuit capacity for a larger electric element
- Any code items caught during the swap
Frequently asked questions
Licenses, credentials, and company proof
- Colorado Master PlumberLicense MP-00189274
- Colorado State Plumbing ContractorLicense 2110
- Family Owned & OperatedServing Denver since 2006, 20 years
- Better Business BureauAccredited Business, A+ rating
- Angie's List Super Service Award2012 through 2017
- Serving Denver since 2006Residential and commercial properties across the metro
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Not sure which size fits your house?
Tell us your bathrooms and morning routine. We will size it.