A water heater that's too small runs out of hot water during showers; one that's too large wastes energy. This calculator recommends the right tank size based on your household's bedrooms and bathrooms.
Home Details
Scenario: Your home has 3 bedrooms and 2 bathrooms.
Result: Estimated occupants: 4. First hour demand: 48 gallons. Recommended tank: 50 gallons. Tankless alternative: 4.0 GPM flow rate for simultaneous use.
For 1-2 people: 30-40 gallons. For 2-3 people: 40-50 gallons. For 3-4 people: 50-60 gallons. For 5+ people: 60-80 gallons. The calculator estimates occupants as bedrooms + 1. The key metric is first-hour delivery (FHD) -- how many gallons of hot water the heater can deliver in the first hour of use.
FHD is the total hot water a heater can deliver in one hour, starting with a full tank. A 50-gallon tank heater might have an FHD of 60-70 gallons because it reheats water while you use it. Match FHD to your peak-hour demand for best results.
Tank heaters cost less upfront ($500-$1,500 installed) and work well for most homes. Tankless heaters cost more ($1,500-$4,000 installed) but last longer, use less energy, and never run out of hot water. Tankless makes sense for high-usage households.
Tank water heaters last 8-12 years. Tankless heaters last 15-20 years. Extend tank life by flushing sediment annually and replacing the anode rod every 3-5 years. Signs of failure: rusty water, rumbling noises, or puddles around the base.
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