Water Heater Calculator

Calculate water heater sizing for tank and tankless systems. Compare gas tank, electric tank, tankless gas, tankless electric, heat pump, and solar water heaters. Includes annual operating costs and 10-year total cost of ownership analysis.

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Tank Size
80 gal
84 gal first-hour
Total Cost
$2,200
installed
Annual Cost
$407
operating
Lifetime
$6,271
10 year total
Tank vs Tankless Comparison
Tank (Selected)Tankless
Upfront Cost$2,200$2,700
Annual Operating$407$250
Expected Lifespan10 yrs20 yrs
Lifetime Cost$6,271$7,693
Recommended Tank Sizes by Household
1-2 People
Tank:30-40 gal
Tankless:2-3 GPM
Apartment/small home
2-3 People
Tank:40-50 gal
Tankless:3-5 GPM
Small family
3-4 People
Tank:50-65 gal
Tankless:5-7 GPM
Average family
4-5 People
Tank:65-80 gal
Tankless:7-9 GPM
Larger family
5-6 People
Tank:80+ gal
Tankless:9-11 GPM
Large family
6+ People
Tank:2 units
Tankless:11+ GPM
May need multiple units
Fuel Type Comparison
FuelCost/UnitTank Eff.Tankless Eff.Notes
Electric$0.12/kWh92%99%Widespread, easy install, higher operating cost
Natural GasSelected$1.2/therm67%95%Most common, lower operating cost
Propane (LP)$2.5/gallon60%90%Rural areas, requires tank
Heat Pump (Hybrid)$0.12/kWh92%99%2-3x more efficient than standard electric

How to Use Water Heater Calculator

  1. 1Enter household size and usage level
  2. 2Select current heater type
  3. 3Compare 6 water heater types
  4. 4View sizing and 10-year cost of ownership

Frequently Asked Questions

What size water heater do I need?

A family of 2-3 needs a 40-50 gallon tank or 5-7 GPM tankless. Family of 4-5 needs a 50-80 gallon tank or 7-9 GPM tankless. Base sizing on peak hour demand — the first hour rating should exceed your busiest hour's hot water usage.

Is tankless worth the extra cost?

Tankless heaters cost 2-3x more upfront but save 20-30% on water heating energy annually and last 20+ years (vs 10-15 for tank). They pay for themselves in 8-12 years. Best for homes with consistent moderate demand rather than extreme peak usage.

What is the most efficient water heater?

Heat pump water heaters are the most energy-efficient (2-3x more efficient than standard electric), saving $200-400/year. Solar water heaters save the most in sunny climates. For gas, tankless condensing units achieve 95%+ efficiency.

About Water Heater Calculator

Calculate water heater sizing for tank and tankless systems. Compare gas tank, electric tank, tankless gas, tankless electric, heat pump, and solar water heaters. Includes annual operating costs and 10-year total cost of ownership analysis.

NexTool's Water Heater Calculator is completely free to use with no sign-up required. Your data is processed directly in your browser and never sent to our servers, ensuring complete privacy and instant results.

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