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HVAC

HVAC Capacity Calculator

Check whether an existing HVAC system has the capacity for the space it serves, for heating and cooling.

Your numbers

sq ft
tons
BTU/h

Result

Cooling needed 3.7 Tons
Heating needed 80,000 BTU per hour
Cooling difference -0.7 Positive means spare capacity
Heating difference 0
The space needs about 3.7 tons of cooling. The installed system is -0.7 tons short.

A rule-of-thumb estimate for early conversations. Equipment should be selected on a room-by-room load calculation (ACCA Manual J) and the ducts designed to match (Manual D). Oversized equipment short-cycles, dehumidifies poorly and wears out early, so guessing high is not the safe option it looks like.

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Questions

About this calculator

My system is oversized. Does it matter?

Usually yes, for comfort rather than for cost. Short cycles remove less moisture, so the house feels clammy even at the right temperature, and the compressor sees more starts.

Why do heating and cooling needs differ so much?

They are driven by different things. Cooling is dominated by sun, windows and humidity; heating by the temperature difference and air leakage. A house can be well matched for one and badly matched for the other.

The formula

cooling tons = area x climate BTU per sq ft / 12,000

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Estimating is the easy part

The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.