Heat Pump Size Calculator
Estimate preliminary heat-pump heating capacity, cooling tons, thermal kilowatts, electrical input and daily operating cost.
Default project preview
68,310 BTU/h
Cooling-ton equivalent
5.69 tons
Electrical input
6.67 kW
Daily electricity
53.4 kWh
Daily energy cost
$9.61
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Conditioned floor area
Enter this project assumption in ft². The current imperial default is 1800 ft².
Average ceiling height
Enter this project assumption in ft. The current imperial default is 8 ft.
Base heating load rate
Enter this project assumption in BTU/h per ft². The current imperial default is 30 BTU/h per ft².
Insulation adjustment
Enter this project assumption in factor. The current imperial default is 1 factor.
Climate adjustment
Enter this project assumption in factor. The current imperial default is 1.15 factor.
Capacity reserve
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 30.
Heating COP
Enter this project assumption in a unitless value. The current imperial default is 3.
Equivalent full-load hours
Enter this project assumption in hours/day. The current imperial default is 8 hours/day. Minimum: 0. Maximum: 24.
Electricity price
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
How to read the outputs
Cooling-ton equivalent
capacity conversion only. Default preview: 5.69 tons.
Electrical input
at COP 3. Default preview: 6.67 kW.
Daily electricity
8 full-load hours. Default preview: 53.4 kWh.
Daily energy cost
entered electricity rate. Default preview: $9.61.
Height factor
relative to standard ceiling. Default preview: 1.
Combined adjustment
insulation × climate. Default preview: 1.15.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Base load uses area × entered load rate. Ceiling height, insulation, climate and reserve factors adjust thermal capacity. Electrical input = thermal capacity ÷ COP.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 29, 2026
Use this calculator for an early heating or cooling capacity scenario based on area and editable load assumptions. Final heat-pump selection requires a room-by-room load calculation and equipment performance at design conditions.
Calculation steps
- 1Use conditioned floor area only.
- 2Select a preliminary load intensity based on known building characteristics.
- 3Compare heating and cooling scenarios.
- 4Verify final capacity with an accepted load method and manufacturer performance tables.
Worked numerical example
A 2,000 ft² house at an assumed 25 BTU/h·ft² produces a 50,000 BTU/h scenario, or about 4.2 nominal tons. That is not a substitute for measured envelope and climate inputs.
Purchasing and rounding
Equipment is sold in nominal capacity steps, but larger is not automatically better. Oversizing can reduce comfort, efficiency and dehumidification.
Interpret the result
The result is a screening range. Climate, insulation, windows, infiltration, ventilation and internal gains can move the real load substantially.
Page-specific assumptions
- Uniform load intensity.
- Conditioned area is measured correctly.
- No detailed room or orientation effects.
- Rated capacity is adjusted later for outdoor temperature.
Common mistakes
- Replacing the existing unit size without a load check.
- Sizing only by square footage.
- Ignoring low-temperature capacity.
- Rounding up excessively for recovery speed.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Heat Pump Size Calculator questions
Why can an oversized heat pump be a problem?+
Oversizing can shorten cycles, reduce comfort and humidity control, and increase cost.
Does rated capacity stay constant in cold weather?+
No. Air-source heat-pump output and efficiency usually change as outdoor temperature changes.
Can this replace a professional load calculation?+
No. Final selection should use an accepted room-by-room load method and manufacturer performance tables.