About the Power Converter
This power converter changes a rate of energy use or output from one unit to another: watts, kilowatts, megawatts, mechanical horsepower, metric horsepower (PS or CV), electrical horsepower, BTU per hour, tons of refrigeration, kilocalories per hour and foot-pounds per second. Enter a value, pick the unit it is in and the unit you want, and every other equivalent is listed below the headline answer.
It is useful when comparing car engine ratings quoted in hp, PS and kW, sizing an air conditioner or heater rated in BTU/h against an electrical load in watts, reading a motor nameplate, or checking a generator against the appliances it has to run.
Power is energy per unit of time, so this tool converts rates (watts), not amounts of energy (watt-hours or kWh). Use the energy converter if your number is in kWh, joules or BTU without the "per hour".
How to use the power converter
- 1Enter the power figure you want to convert.
- 2Choose the unit it is currently in, such as hp or BTU/h.
- 3Choose the unit you want the answer in.
- 4Read the headline conversion, then scan the table for every other unit.
Formula and method
Every unit is stored as its size in watts, so a conversion multiplies by the source unit’s wattage and divides by the target unit’s wattage. One mechanical horsepower is defined as 550 foot-pounds-force per second, which is 745.69987 W; a metric horsepower (PS, CV, pk) is 75 kilogram-force metres per second, exactly 735.49875 W; electrical horsepower is set at 746 W.
BTU per hour uses the International Table BTU (1055.05585262 J), giving 1 BTU/h ≈ 0.293071 W. A ton of refrigeration is 12,000 BTU/h (≈ 3.5169 kW), and 1 kcal/h is 1.163 W using the International Table calorie.
- W
- Watt, one joule per second (SI unit of power)
- hp
- Mechanical horsepower = 745.69987 W
- PS
- Metric horsepower = 735.49875 W
- BTU/h
- British thermal unit per hour ≈ 0.293071 W
Worked examples
1 horsepower to kilowatts
One mechanical horsepower is 550 ft·lbf/s. Multiplying 550 by 1.3558 N·m per ft·lbf gives 745.70 W, which is 0.7457 kW.
1,500 W space heater in BTU/h
One BTU/h equals 1055.05585 J ÷ 3600 s ≈ 0.29307 W, so 1500 ÷ 0.29307 ≈ 5,118 BTU/h — the heat output of a typical plug-in heater.
200 PS car engine in kW and hp
200 × 735.49875 W = 147,099.75 W, or about 147.1 kW. Dividing by 745.70 W gives about 197.3 mechanical horsepower, slightly less than the PS figure.
1 ton of refrigeration in kW
A refrigeration ton is 12,000 BTU/h. At 0.29307 W per BTU/h that is 3,516.9 W, or about 3.52 kW of cooling capacity.
Frequently asked questions
How many watts are in one horsepower?+
One mechanical (imperial) horsepower is about 745.7 W. A metric horsepower (PS) is 735.5 W, and the electrical horsepower used on motor ratings is exactly 746 W.
How do I convert kW to hp?+
Multiply kilowatts by 1.341 to get mechanical horsepower, or by 1.3596 to get metric PS. For example, 100 kW ≈ 134.1 hp ≈ 136 PS.
How many BTU per hour is 1 watt?+
One watt is about 3.412 BTU/h. So a 1,000 W device produces or moves roughly 3,412 BTU/h, and a 12,000 BTU/h air conditioner has about 3.5 kW of cooling capacity.
What is the difference between kW and kWh?+
kW measures power, the rate of energy use at a moment. kWh measures energy used over time: a 2 kW heater running for 3 hours uses 6 kWh. This tool converts power units only.
Is PS the same as bhp?+
No. PS (Pferdestärke) is metric horsepower, 735.5 W. Brake horsepower (bhp) is usually mechanical horsepower measured at the crankshaft, 745.7 W, so a 100 PS engine is about 98.6 bhp.