Power and Heat Converter
kW, horsepower, kcal/h, BTU/h and tons of refrigeration.
Quick answer
With the default inputs: Value 1 · From unit Kilowatt · To unit Metric horsepowerConverted value 1.3596 PS
Edit the inputs below to recalculate.Inputs
Result
Converted value
1.3596PS
| Kilowatt | 1kW |
| Watt | 1000.00W |
| Megawatt | 0.001MW |
| Mechanical horsepower | 1.341hp |
| Metric horsepower | 1.3596PS |
| Kilocalorie per hour | 859.8452kcal/h |
| BTU per hour | 3412.14BTU/h |
| Ton of refrigeration | 0.284345RT |
| Foot-pound per second | 737.561ft·lb/s |
Conversions use 1 kcal = 4.1868 kJ and 1 BTU = 1.05506 kJ. Cooling capacity must come from a load calculation, not area times a rule of thumb.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
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 |
How to work it out
- Separate electrical power from cooling or heating capacity first. kW can mean either, so confirm whether a data sheet quotes input power or output capacity — it changes how efficiency is calculated.
- Basic relations: 1 kW = 1000 W and 1 MW = 1000 kW. Electrical power is the simplest conversion here.
- Two kinds of horsepower: 1 mechanical horsepower (hp) = 0.7457 kW, and 1 metric horsepower (PS) = 0.7355 kW — 1.4% apart, with imported and domestic equipment using different conventions.
- Heat: 1 kcal/h = 1.163 W and 1 kW = 860 kcal/h; 1 BTU/h = 0.2931 W and 1 kW = 3412 BTU/h. These are the core conversions in HVAC and refrigeration.
- Cooling: 1 refrigeration ton (US) = 3.5169 kW = 3024 kcal/h = 12,000 BTU/h. A Japanese ton of refrigeration is 3.861 kW, 9.8% larger, and appears occasionally in Japanese data.
- The electricity-heat bridge: 1 kWh = 860 kcal = 3412 BTU, valid only where electricity converts wholly to heat. It does not apply to heat pumps with a COP above 1.
Where it goes wrong
- Reading a refrigeration ton as electrical power. One ton is 3.517 kW of cooling, not of consumption — a one-ton unit draws about 1.1 kW at COP 3.2, so treating it as 3.5 kW triples the running-cost estimate.
- Mixing mechanical and metric horsepower. Compressor and pump data use both hp and PS, and 0.7457 against 0.7355 differs by 1.4% — about 1 kW on a 75 kW machine.
- Approximating BTU/h to W as 1:3. One BTU/h is 0.293 W, so 1 W is 3.41 BTU/h; reversing the direction is an elevenfold error.
- Using 1 kWh = 860 kcal for heat pump output. A heat pump delivers 3-4 kWh of heat per kWh of electricity at COP 3-4; the identity holds only for direct electric heating.
- Adding kcal and kW in the same load calculation. Design loads are in kW while older data is in kcal/h at 1 kW = 860 kcal/h — summing without converting is out by 860.
Material and cost
Power unit errors drive both equipment selection and running cost. Reading a 100 kW chiller as 28 refrigeration tons mis-selects the machine by hundreds of thousands; misjudging connected load distorts the annual electricity estimate by tens of thousands; and in a capacity application to the utility it causes either rejection or wasted capacity.
On site
- Quick cooling load: dwellings 100-150 W/m², offices 120-180, restaurants 200-250. Note that the trade term pi equals about 2.5 kW of cooling, not 0.735 kW of electrical input — an easy confusion.
- Efficiency metrics: domestic air conditioners above APF 3.5 reach grade 1, and chillers above COP 5.0 are strong. Higher is better, but always compare at the same conditions.
- Transformer sizing: 50-100 W/m² of built area (low for housing, high for retail), divided by 0.85 power factor for kVA.
- Allow 10-15% margin on motor rating but no more. An oversized motor runs at low load where both efficiency and power factor fall, wasting energy.
Basis
- GB/T 3100-3102 Quantities and units series
- GB 19577-2015 Minimum allowable values of energy efficiency and energy efficiency grades for chillers
- GB 21455-2019 Minimum allowable values of energy efficiency and energy efficiency grades for room air conditioners
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.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Power and Heat Converter. 2026-10-25. https://jianzhujisuan.com/en/unit-power
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.