Water Heater Cost by Size: 40 vs 50 vs 80 Gallon Compared
Updated 2026-07-09
Bigger is not automatically better here, and getting it wrong costs you either way: too small means cold showers, too big means paying to heat water nobody uses. A 40 gallon unit runs $600 to $1,400 installed and suits two to three people. A 50 gallon runs $700 to $1,800 and covers most three-to-five-person households. Large 75 to 80 gallon units for five or more run $1,000 to $2,200.
Cost by tank size
| Tank size | Best for | Unit cost (gas) | Unit cost (electric) | Installed total |
|---|---|---|---|---|
| 30 gallon | 1 to 2 people | $300 to $600 | $250 to $500 | $500 to $1,100 |
| 40 gallon | 2 to 3 people | $400 to $900 | $300 to $700 | $600 to $1,500 |
| 50 gallon | 3 to 5 people | $500 to $1,100 | $400 to $900 | $700 to $1,800 |
| 75 to 80 gallon | 5 to 7 people | $700 to $1,400 | $600 to $1,200 | $1,000 to $2,200 |
Pick 40 gallons if
- You are a couple or a single-person household. A 40 gallon tank matches typical use without waste.
- You run a low-occupancy rental. Lower unit cost and standby loss both work in a landlord's favor here.
- Space is genuinely tight. A smaller footprint fits utility closets a 50 or 80 gallon unit physically cannot.
Pick 50 gallons or larger if
- Three or more people share the bathroom schedule. The buffer against back-to-back morning showers is worth the modest $100 to $200 step up.
- The house has a soaking tub. A standard tub holds 60 to 80 gallons and will drain most 40 to 50 gallon tanks on its own.
- Five or more people live there. Move to 75 to 80 gallons, or seriously consider tankless instead.
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The number that matters more than gallons
Tank size is only half the story. The First Hour Rating, printed on the Energy Guide label, tells you how many gallons the unit actually delivers in the first hour from a full, heated tank. A 50 gallon unit with a strong burner and high FHR can outperform a sluggish 75 gallon tank. A household drawing 80 gallons in the first hour of a busy morning needs a unit with an FHR of at least 80, regardless of what the gallon number on the front says.
What oversizing actually costs you
More water held at temperature means more standby energy loss, roughly $20 to $40 a year for a 40-to-50-gallon step and $40 to $80 for 50-to-80. Real money, but rarely the deciding factor next to the cost of running out of hot water every morning, which has its own price tag, just a less visible one.
FAQs
What happens if I replace a 40 gallon with a 50 gallon?
In most cases the swap is straightforward since the connections sit in the same place. A plumber may adjust water lines slightly for height differences between models, adding $50 to $150 in labor. The clearance check is typically a 30-minute task, not a project complication.
Do larger tanks cost more to install, not just to buy?
Barely. Installation cost is driven mostly by labor complexity, not tank size, so a 40-to-50-gallon step adds almost nothing to the install portion of the bill. The unit price moves; the labor line mostly does not.
Related guides
- The full installed cost breakdown
- Whether tankless solves the sizing problem
- Fuel type cost comparison
Which size wins
For most three-or-more-person households, 50 gallons is the right balance of cost and capacity. Move up to 75 to 80 gallons for larger families or heavy daily use. Use the calculator to see installed cost by size for your area, then confirm with a licensed plumber before ordering.