Estimate heat pump capacity from room loads quickly. Compare BTU, tons, airflow, and demand clearly. Make better system choices with practical engineering insight today.
| Item | Example Value |
|---|---|
| Floor Area | 1800 ft² |
| Ceiling Height | 8.5 ft |
| Indoor / Outdoor Design Temperature | 70°F / 20°F |
| Envelope Multiplier | 2.7 |
| Average U-Value | 0.08 |
| Air Changes Per Hour | 0.60 |
| Internal Heat Gains Offset | 1200 BTU/hr |
| Duct Loss | 8% |
| Calculated Capacity | 33,271.53 BTU/hr |
| Estimated Tonnage | 2.77 tons |
| Estimated Electrical Input | 2.95 kW |
| Estimated Monthly Cost | $141.60 |
1. Room Volume: Volume = Floor Area × Ceiling Height
2. Envelope Area: Envelope Area = Floor Area × Envelope Multiplier
3. Transmission Load: Transmission Load = Envelope Area × U-Value × Temperature Difference
4. Infiltration Airflow: CFM = (ACH × Volume) ÷ 60
5. Infiltration Load: Infiltration Load = 1.08 × CFM × Temperature Difference
6. Net Load: Net Load = Transmission Load + Infiltration Load − Internal Gains
7. Adjusted Load: Adjusted Load = Net Load × Climate Factor × Safety Factor
8. Required Capacity: Capacity = Adjusted Load ÷ (1 − Duct Loss Fraction)
9. Tonnage: Tons = Capacity ÷ 12,000
10. Thermal kW: Thermal Output = Capacity × 0.00029307107
11. Electrical Input: Electrical kW = Thermal Output ÷ COP
12. Supply Airflow: Airflow = Capacity ÷ (1.08 × Supply-to-Room Temperature Rise)
Heat pump capacity shows how much heat a system can deliver each hour. Correct sizing improves comfort. It also supports better efficiency. A unit that is too small may run constantly. A unit that is too large may cycle too often. Both cases can reduce performance and increase wear.
This calculator estimates heating demand from several practical inputs. It uses floor area, ceiling height, design temperatures, envelope quality, and air leakage. It also includes duct loss, climate adjustment, and safety margin. These values help create a more realistic engineering estimate. The result is shown in BTU per hour, tons, thermal kilowatts, and electrical input.
The temperature difference between indoors and outdoors drives heat loss. When outdoor air gets colder, the system must supply more heat. That is why design temperature matters. A building in a mild region usually needs less capacity. A building in a severe winter region usually needs more capacity.
Heat escapes through walls, windows, ceilings, and floors. This is the transmission load. Air leakage adds another load. That is the infiltration load. Homes with poor sealing often need higher heating capacity. Better insulation and air sealing can reduce both load and operating cost.
COP describes how efficiently the heat pump converts electrical input into useful heat. A higher COP usually means lower electrical demand for the same heating output. Airflow also matters. If airflow is too low, delivered heat may not match the design target. This calculator estimates required supply airflow to support sizing decisions.
This tool is helpful for planning, comparison, and early engineering review. It works well for rough equipment selection and budget checks. Final equipment sizing should still consider manufacturer data, local weather, defrost behavior, and detailed room-by-room calculations. Use the output to narrow options and improve decisions before final specification.
Heat pump capacity is the amount of heat a unit can deliver in one hour. It is usually shown in BTU/hr, tons, or kilowatts.
Design temperatures set the heating difference the system must overcome. Larger temperature gaps create larger heating loads and require more capacity.
One ton equals 12,000 BTU per hour. It is a common HVAC sizing unit used for both cooling and heating discussions.
Air changes per hour estimate infiltration. Outdoor air entering the space must be heated. That adds to the total heat pump capacity requirement.
COP shows heating efficiency. A higher COP means less electrical input is needed for the same thermal output, which can reduce operating cost.
A modest safety factor can help with uncertainty. Very large safety factors can oversize equipment, so they should be used carefully.
No. This tool is a strong planning estimate. Final design should use detailed load methods, local codes, and manufacturer performance tables.
Supply air temperature helps estimate airflow. The calculator uses the temperature rise between supply air and room air to find required CFM.