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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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.
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.
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.
Using the Water Heater Calculator is simple: visit the tool page, enter your data or input into the provided fields, and get instant results. No downloads, installations, or sign-ups are required. The tool runs directly in your web browser for maximum convenience.
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The Water Heater Calculator uses industry-standard formulas and algorithms to deliver reliable results. While the tool is designed for accuracy, results should be used as estimates and guidance. For critical decisions, always consult a qualified professional.
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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 (Selected) | Tankless | |
|---|---|---|
| Upfront Cost | $2,200 | $2,700 |
| Annual Operating | $407 | $250 |
| Expected Lifespan | 10 yrs | 20 yrs |
| Lifetime Cost | $6,271 | $7,693 |
| Fuel | Cost/Unit | Tank Eff. | Tankless Eff. | Notes |
|---|---|---|---|---|
| Electric | $0.12/kWh | 92% | 99% | Widespread, easy install, higher operating cost |
| Natural GasSelected | $1.2/therm | 67% | 95% | Most common, lower operating cost |
| Propane (LP) | $2.5/gallon | 60% | 90% | Rural areas, requires tank |
| Heat Pump (Hybrid) | $0.12/kWh | 92% | 99% | 2-3x more efficient than standard electric |