What Size Water Heater Do You Need?
Calculate the right water heater capacity for your household. Tank size by family size, usage patterns, and climate.
Sizing a Water Heater
The key metric is First Hour Rating (FHR) — how many gallons of hot water the heater can deliver in one hour starting with a full tank. Calculate your peak hour demand: showers (10 gal each), dishwasher (6 gal), washing machine (7 gal), faucets (2 gal each). Add up everything that runs during your busiest hour. Your FHR should exceed this number.
Tank Size Guidelines
1-2 people: 30-40 gallons. 3-4 people: 40-50 gallons. 5+ people: 50-80 gallons. These assume average usage. High-usage households (multiple showers back-to-back, daily baths, frequent laundry) should size up one tier. Gas heaters recover faster than electric, so a 40-gallon gas can serve the same household as a 50-gallon electric.
Tank vs Tankless vs Heat Pump
Tank: Lower upfront cost ($800-1,500 installed), simple maintenance, limited hot water supply. Tankless: Endless hot water, 20-30% more energy efficient, higher cost ($2,000-4,500 installed), may need gas line upgrade. Heat pump (hybrid): Most energy efficient (50-65% less energy than standard electric), works best in warm/moderate climates, higher upfront ($2,500-4,000) but lowest operating cost.
The heat pump water heater is the biggest energy savings opportunity in most homes. It uses 50-65% less electricity than a standard electric tank by extracting heat from surrounding air. The $300 federal tax credit and many state/utility rebates can reduce the price premium to near zero.
