BTU to kW Calculator
Convert HVAC cooling or heating capacity (BTU/hr) to electrical input power (kW & kVA). Crucial for sizing generators for Air Conditioners and Heaters.
Equipment Details
Required Input Power
Estimated Starting Surge (AC Only)
Understanding BTU to kW Conversion
Converting thermal energy (BTU/hr) to electrical input power (kW) depends heavily on the type of equipment.
-
Electric Resistance Heating: This is nearly 100%
efficient. The conversion is pure physics:
1 kW = 3412 BTU/hr. -
Air Conditioning (Cooling): This uses a heat pump
cycle. The electrical input is much lower than the cooling output.
We use the Energy Efficiency Ratio (EER) to
convert.
Input Watts = BTU / EER.
Note: Starting surge for AC units is typically 3x to 5x the running watts. This calculator estimates that surge based on typical Locked Rotor Amp (LRA) characteristics.
Common AC Sizes (Approximate)
| Capacity (BTU) | Tonnage | Est. Running Watts (EER 10) | Est. Starting Watts |
|---|---|---|---|
| 5,000 | ~0.4 Ton | 500 W | 1,500 W |
| 12,000 | 1.0 Ton | 1,200 W | 3,600 W |
| 24,000 | 2.0 Ton | 2,400 W | 7,200 W |
| 36,000 | 3.0 Ton | 3,600 W | 10,800 W |
| 48,000 | 4.0 Ton | 4,800 W | 14,400 W |
Recommended BTU Equipment
Top-rated air conditioners and heaters based on capacity.
5,000 BTU Window AC
Perfect for small rooms up to 150 sq ft. Energy efficient and easy to install.
12,000 BTU Portable AC
Cools rooms up to 550 sq ft. Mobile design with easy window venting kit.
24,000 BTU Mini Split AC
High efficiency ductless system for large spaces up to 1,500 sq ft. Includes heat pump.
1,500W Space Heater
Provides ~5,100 BTU of heating. Ceramic oscillating heater for quick personal warmth.
5,000W Garage Heater
Heavy duty 240V heater providing ~17,000 BTU for workshops and garages.
Inverter Generators
Quiet, clean power to run your AC or heater. Perfect for RVs and home backup.