Water Heater Size Calculator
Calculate the right water heater size for your household. Get recommendations for tank (storage) or tankless (on-demand) water heaters based on household size, number of bathrooms, and usage patterns.
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Frequently asked questions
What is the difference between tank and tankless water heaters?
Tank heaters store hot water in a reservoir (30–80 gallons) and keep it heated continuously. Tankless heaters heat water on demand as it flows through the unit, eliminating standby heat loss. Tankless units typically cost more upfront but save energy and last longer.
How long does a water heater last?
Traditional tank water heaters last 8–12 years. Tankless models last 15–20+ years. Signs you need a replacement: rusty water, rumbling noises from the tank, water around the unit, or inconsistent hot water.
What size water heater do I need for a family of 4?
A family of 4 with average usage typically needs a 40–50 gallon tank heater. If usage is high (long showers, frequent bathing, high-efficiency washer), size up to 50–65 gallons. For tankless, a 6–8 GPM unit handles most 2-bathroom homes.
Gas vs electric water heater — which is better?
Gas heaters heat water faster and have lower operating costs in most US markets. Electric heaters have lower upfront costs and are 100% efficient at the point of use (no flue losses). Heat pump water heaters (electric) are the most energy-efficient option, using 2–3× less energy than standard electric.
When should I replace my water heater?
Replace it if it's more than 10 years old, shows signs of corrosion or leaking, takes much longer to heat water, or requires frequent repairs. Proactive replacement before failure avoids water damage and gives you time to select the right model.