In water heating, capacity refers to how much hot water a system can deliver. For tank models, it is measured in gallons stored; for tankless systems, it is measured in gallons per minute (GPM) delivered at a given temperature rise. Proper capacity sizing ensures enough hot water during peak demand without wasting energy.
/kəˈpæsɪti/
In water heating, capacity refers to how much hot water a system can deliver. For tank models, it is measured in gallons stored; for tankless systems, it is measured in gallons per minute (GPM) delivered at a given temperature rise. Proper capacity sizing ensures enough hot water during peak demand without wasting energy.
What does capacity mean for a water heater?
It describes how much hot water the system can provide—measured in tank gallons or tankless GPM at a given temperature rise.
Source: The Cooling Company
Capacity varies by tank size, GPM, and temperature rise.
A family of four often chooses a 50–60 gallon tank for back-to-back showers, while a single-person home may use a smaller tank or tankless system.
Estimate peak hour hot water demand and pick a capacity that meets or slightly exceeds it to avoid running out of hot water.
“Estimate peak hour hot water demand and pick a capacity that meets or slightly exceeds it to avoid running out of hot water.”
On-demand and solar water heaters can meet capacity needs while improving energy efficiency.
How do I size water heater capacity?
Estimate peak hour demand from showers, laundry, and dishwashing, then choose a tank size or GPM rating that meets it.
What happens if capacity is too small?
You may run out of hot water during peak times or experience temperature drops.
Is bigger always better?
Not always. Oversized units can waste energy, so right-sizing is best.
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