Hot Water Demand Calculator

Hot water is bought in two currencies: the daily total that drives the fuel bill, and the peak-hour surge that forces the tank size. This tool produces both.

Hot Water Demand Calculator estimates daily and peak demand from your building type, occupants and fixtures, then points to a tank size.

• Building-type method: per-person daily gallons by use.
• Fixture method: count showers, tubs, laundry, kitchens.
• Daily and peak: both sizing currencies.
• Tank pointer: FHR-based tank recommendation.
• Export: Copy or download the report.

1. Pick the building type.
2. Enter occupants and count the hot fixtures.
3. Read daily and peak-hour demand.
4. Note the tank pointer and carry the peak into the tank tool.

Example - 4-person single-family. 4 x 20 = 80 gal/day, peak ~24 gal. Two showers and a laundry put the fixture method near 60 gal/day - use the larger, and the tank sizing lines up with a 40-50 gal unit.

• Two methods, one answer: cross-checked, defensible.
• Any building type: homes to hotels to offices.
• Feeds every heater tool: one demand number upstream.
• Free and private: no uploads, no logging.