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Find the right water heater capacity for your household
Tell us about your household to determine the right water heater size
Nothing ruins a morning faster than running out of hot water mid-shower. Or worse, realizing your water heater is working overtime (and running up your utility bill) because it's way bigger than you actually need.
Sizing a water heater isn't as simple as "bigger is better." You need to match the tank capacity (or flow rate for tankless) to your household's actual hot water usage. Get it wrong, and you're either shivering through cold showers or paying to keep 80 gallons of water hot when you only use 40.
Our water heater calculator takes the guesswork out of sizing. Answer a few questions about your household, and we'll recommend the right capacity for both traditional tank and tankless options.
Water heater sizing depends on peak demand—the most hot water you'll use at any one time. Here's what we factor in:
An oversized tank water heater keeps more water hot than you need, wasting energy 24/7. Proper sizing can cut water heating costs by 10-15%.
An undersized heater means cold showers and waiting for recovery. Right-sizing ensures hot water when you need it.
Properly sized heaters cycle less frequently and experience less stress, typically lasting 2-3 years longer.
Why take up space with an 80-gallon tank when a 50-gallon (or tankless) would serve you perfectly?
Mistake: Just replacing with the same size
Solution: Your hot water needs may have changed since your last heater was installed. Kids grow up, people move out, low-flow fixtures get installed. Always recalculate.
Mistake: Ignoring recovery rate
Solution: A 40-gallon tank with a fast recovery rate can outperform a 50-gallon with slow recovery. Consider how quickly the heater can reheat.
Mistake: Not accounting for cold inlet water temperature
Solution: In northern climates, incoming water can be 40°F. In the south, it might be 70°F. Colder inlet water means your heater works harder.
Mistake: Choosing tankless without checking flow requirements
Solution: Tankless heaters have flow rate limits. If you want to run two showers and a dishwasher simultaneously, make sure your unit can handle it.
While our calculator gives you a solid recommendation, call a plumber when:
Generally, a family of 4 does well with a 50-65 gallon tank water heater, or a tankless unit rated for 7-9 GPM. But this varies based on usage patterns—if everyone showers in the morning, you might need more capacity.
It depends. Tankless heaters are more energy-efficient and last longer, but cost more upfront and have flow limitations. If you have low-to-moderate hot water demand spread throughout the day, tankless can be great. For high-demand households, a large tank or multiple tankless units might be better.
Tank water heaters typically last 8-12 years. Tankless can last 15-20+ years. Proper sizing helps maximize lifespan because the unit isn't constantly stressed by running at capacity.
Not necessarily. A slightly oversized tank wastes energy keeping extra water hot. It's better to size accurately and add a small buffer (10-15%) rather than going significantly larger.