Mechanicals · definition
How much hot water a heater delivers in a peak hour (tank) or gallons-per-minute (tankless). The right sizing metric, not just tank gallons.
Source: A. O. Smith — What Is First Hour Rating?
Where this term lands on a Columbus budget
The cost pages carry the current local ranges, and the guides explain what moves them. A published range becomes a project number only after someone looks at the site.