Commercial gas water heaters from 80,000 through 360,000 Btu/h, in atmospheric, power-vent and condensing configurations.
Commercial sizing works from first-hour rating rather than tank volume. The units here deliver from 264 to 419 gallons in the first hour, and that figure — storage plus recovery combined — is what determines whether a restaurant or a locker room runs out at peak. A large tank with slow recovery and a small tank with fast recovery can carry the same rating.
Efficiency splits the range roughly in half. Units at 90% and above are condensing: they extract enough heat to condense flue gas, which means PVC or stainless venting and a condensate drain with neutralization, since the condensate is acidic. Below 90% the appliance uses conventional metallic venting.
That difference decides the installation cost more than the appliance price does — a condensing replacement in a building plumbed for atmospheric venting means new vent, new drain and often a new gas line.
Connections are 1-1/2" and 2" MIP. Brands include Rheem and Noritz.
