Power and Heat Converter
kW, horsepower, kcal/h, BTU/h and tons of refrigeration.
Inputs
Result
Formula
| Base | 1 kW = 1000 W, 1 MW = 1000 kW |
| Horsepower | 1 hp = 0.7457 kW, 1 PS = 0.7355 kW |
| Heat | 1 kcal/h = 1.163 W, 1 kW = 860 kcal/h |
| Anglo-American heat | 1 BTU/h = 0.2931 W |
| Cooling | 1 RT = 3.5169 kW = 3024 kcal/h = 12000 BTU/h |
| Energy | 1 kWh = 860 kcal = 3412 BTU |
1 kW is 1.3596 hp, 860 kcal/h, 3412.14 BTU/h or 0.2843 RT. A 5 PS (3.675 kW) air conditioner is about 1.05 refrigeration tons.
Air conditioner rating and cooling capacity
| Horsepower (PS) | Input kW | Cooling kW | Cooling kcal/h | Typical area m² |
|---|---|---|---|---|
| 1 PS | 0.735 | 2.50 | 2150 | 10-15 |
| 1.5 PS | 1.103 | 3.50 | 3010 | 15-22 |
| 2 PS | 1.471 | 5.00 | 4300 | 22-30 |
| 3 PS | 2.205 | 7.20 | 6190 | 30-45 |
| 5 PS | 3.675 | 12.00 | 10320 | 50-70 |
FAQ
Is an air conditioner's “horsepower” power or cooling?
Strictly it is input power, 735.5 W per PS, but in shops “1 hp” means about 2500 W of cooling because the efficiency ratio is around 3.4. That is why two nominally identical units differ by 20% in capacity. Always size on the nameplate cooling capacity in kW, not the horsepower.
Why do mechanical and metric horsepower differ?
Mechanical horsepower is 550 ft·lb per second (745.7 W) and metric horsepower is 75 kgf·m per second (735.5 W), 1.4% apart. European equipment uses PS and American uses hp, so on a large motor 1.4% is a whole kilowatt — allow headroom when sizing drives.
Why is one refrigeration ton 3.5 kW?
It comes from ice melting: one US ton of refrigeration is the power to melt one short ton (907 kg) of ice at 0°C in 24 hours — 907 × 333.5 kJ ÷ 86400 s ≈ 3.5 kW. The Japanese ton uses 1000 kg and gives 3.86 kW, 10% more, so check imported units carefully.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.