HomeExpertly
www.homeexpertly.comWater Heater Size Calculator
Size a tank, tankless, or heat pump water heater from your real peak-hour use — first-hour rating, flow rate and temperature rise — with U.S. pricing, annual energy cost, a model comparison, and a downloadable PDF.
Tanks are sized by peak-hour demand; tankless units by flow rate at your temperature rise — cold incoming water shrinks a tankless unit's output fast. Estimates use 2024-2025 U.S. prices. For planning purposes only — venting, gas line, and electrical work need a licensed pro.
Household & Heater
1
Household & Peak Hour
people
baths
Tick what runs in your busiest hour. Tank sizing adds the gallons; tankless sizing adds the flow of anything that could overlap.
gal / day
Used for the annual energy cost, not for sizing.
2
Heater & Temperature
°F out
120°F is the U.S. standard — hot enough, and it will not scald.
3
Equipment & Energy Cost
$unit
Auto-filled from the recommended size — type over it with a real quote.$total
Swap-in tank ~$500-$1,000. Tankless (venting + gas line) ~$1,200-$2,500.$/ therm
U.S. residential natural gas ~$1.10 - $1.70 per therm.
Water Heater Estimate
Recommended Size
—
Tick the fixtures in your busiest hour
Peak-Hour Demand
—
Peak Flow Needed
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Temperature Rise
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Full Cost Breakdown
What this model delivers —
Unit —
TOTAL, FIRST YEAR—
Energy use / year
—
Energy cost / year
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Upfront (unit + install)
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Cost Breakdown Chart
Estimated cost by category ($)
Model Comparison — Your Demand
| Model | Delivers | You Need | Fits? | Est. Unit Cost |
|---|