About This Calculator

Tankless Water Heater Sizing Calculator is an independent resource for US homeowners. Match peak hot-water demand and temperature rise to tankless capacity. Our guidance draws on manufacturer flow tables, installation manuals and other published sources, and we have not lab-tested any heater. Whether a tankless model suits a house comes down to its exact flow curve at your winter temperature rise and the fuel, venting or electrical service available. For corrections, use the contact page.