Water Heater Size Calculator

HVAC CALCULATOR

Estimate the storage water heater tank size your household may need based on family size, bathrooms, showers, appliances, and peak hot-water use.

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1. Household

Tell us how many people regularly use hot water in the home.

Number of People

Number of Bathrooms

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2. Peak-Hour Hot Water Use

Think about the busiest hour of the day—usually morning or evening.

Showers During Peak Hour One normal shower is estimated at approximately 17 gallons of hot water.

Average Shower Length

Baths During Peak Hour

Hand / Bathroom Sink Uses

Kitchen Sink Uses

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3. Hot-Water Appliances

Include appliances likely to run during the same peak hour.

Dishwasher Approx. 6 gallons Clothes Washer Approx. 15 gallons Additional Hot-Water Use Add approx. 5 gallons

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4. Household Hot-Water Usage

Choose the option that best matches your household.

Overall Usage Level

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5. Water Heater Type

Recovery performance can differ depending on the type of water heater.

Water Heater

Water Heater Set Temperature

°F

YOUR ESTIMATE

Recommended Water Heater Size

Based on your estimated peak-hour hot-water demand.

50 Gallon Tank

A 50-gallon water heater may be a good starting point.

Estimated Peak-Hour Demand 0 gallons

Suggested Minimum FHR 0 gallons

Household Size 0 people

Usage Level Typical

Estimated Peak-Hour Usage

Showers 0 gal

Baths 0 gal

Bathroom / Hand Sinks 0 gal

Kitchen Sink 0 gal

Dishwasher 0 gal

Clothes Washer 0 gal

Estimated Peak-Hour Demand 0 gal

Typical Storage Water Heater Sizes

30–40 gal 1–2 people

40–50 gal 2–3 people

50–60 gal 3–4 people

60–80 gal 4–6+ people

These are broad starting ranges. Peak-hour demand and the manufacturer’s First Hour Rating matter more than household size alone.

💡 Don’t Look at Tank Size Alone

Two 50-gallon water heaters can provide very different amounts of hot water during a busy hour.

Check the manufacturer’s First Hour Rating (FHR). Ideally, the water heater’s FHR should meet or slightly exceed your household’s estimated peak-hour hot-water demand.

Important: This calculator provides a preliminary storage water-heater sizing estimate for educational and planning purposes. Actual hot-water demand can vary based on fixture flow rates, incoming water temperature, set temperature, recovery rate, household habits, and equipment specifications. Always verify tank size and First Hour Rating with the water-heater manufacturer or a qualified plumbing/HVAC professional.

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