Power Converter
Power converter for engines and electronics — watts, kilowatts, and horsepower.
Convert between watts, kilowatts, megawatts, horsepower and BTU per hour. Useful for engines, generators, solar systems, air conditioners and electrical appliances.
Popular Power Conversions
- Horsepower to Kilowatt
- Kilowatt to Horsepower
- Horsepower to Watt
- Watt to Horsepower
- BTU per Hour to Kilowatt
- Kilowatt to BTU per Hour
- BTU per Hour to Watt
- Megawatt to Kilowatt
- Kilowatt to Watt
All Power Units
| Unit | Symbol | Definition |
|---|---|---|
| Watt | W | The SI derived unit of power, equal to one joule per second. |
| Kilowatt | kW | Equal to 1,000 watts. |
| Megawatt | MW | Equal to 1,000,000 watts. |
| Horsepower | hp | Originally defined to compare steam engines to draft horses. |
| BTU per Hour | BTU/h | The rate of one British thermal unit of heat transfer per hour. |
How power conversion works
Power is the rate of doing work or transferring energy. The SI unit is the watt (W), equal to one joule per second.
1 MW = 1,000,000 W
1 mechanical horsepower = 745.6999 W = 0.7457 kW
1 BTU/h = 0.293071 W
1 kW = 1.34102 hp = 3412.142 BTU/h
hp to kW: multiply by 0.7457. kW to hp: multiply by 1.34102. BTU/h to W: multiply by 0.29307. W to BTU/h: multiply by 3.41214.
Horsepower to kilowatts chart
| Horsepower (hp) | Kilowatt (kW) |
|---|---|
| 1 hp | 0.7457 kW |
| 5 hp | 3.7285 kW |
| 10 hp | 7.457 kW |
| 50 hp | 37.285 kW |
| 75 hp | 55.9275 kW |
| 100 hp | 74.57 kW |
| 150 hp | 111.855 kW |
| 200 hp | 149.14 kW |
| 300 hp | 223.71 kW |
The horsepower on this page is the mechanical (imperial) horsepower of 550 foot-pounds per second. The European metric horsepower (PS or CV) is slightly smaller at 735.499 W, so a car listed as 100 PS has about 98.6 mechanical hp. Check which one a spec sheet uses.
Air conditioners: tons, BTU/h and kW
AC capacity is often sold in "tons". One ton of refrigeration is 12,000 BTU/h of cooling:
| AC size | Capacity | In kilowatts |
|---|---|---|
| 1 ton | 12,000 BTU/h | 3.517 kW cooling |
| 1.5 ton | 18,000 BTU/h | 5.275 kW cooling |
| 2 ton | 24,000 BTU/h | 7.034 kW cooling |
| 3 ton | 36,000 BTU/h | 10.55 kW cooling |
A 1.5-ton AC delivers about 5.28 kW of cooling. Its electricity use is much lower (typically around 1.5 kW for a standard model, and less for an inverter model), because an air conditioner moves heat rather than creating it. Check the electrical input rating on the label.
kW vs kWh vs kVA
- kW is power, how fast energy is used right now (a 2 kW heater).
- kWh is energy, the amount used over time. Electricity bills charge for kWh: a 2 kW heater running for 3 hours uses 6 kWh.
- kVA is apparent power. For generators and UPS units, real power (kW) = kVA × power factor. At a typical power factor of 0.8, a 5 kVA generator gives about 4 kW.
Where each unit is used
- Watts: light bulbs, chargers, appliances and audio equipment.
- Kilowatts: solar panel systems, generators, electric motors, EV chargers and household load.
- Megawatts: power plants, wind farms and large industrial loads.
- Horsepower: car, motorbike, tractor and pump motor ratings.
- BTU/h: air conditioners, heaters and furnaces.
Common mistakes to avoid
- Confusing kW and kWh. A 5 kW solar system does not produce 5 kWh in an hour unless it is running at full output for that hour.
- Using the wrong horsepower. Mechanical hp (745.7 W), metric hp (735.5 W) and electric hp (746 W) differ by up to 1.5%.
- Reading AC tons as weight. A "1.5 ton" AC describes cooling capacity (18,000 BTU/h), not weight.
- Sizing a generator on kW alone. Motors and compressors draw several times their running power when starting, so leave headroom.
Exact conversion factors
| Unit | Symbol | Exact factor |
|---|---|---|
| Watt | W | 1 W = 1 W |
| Kilowatt | kW | 1 kW = 1000 W |
| Megawatt | MW | 1 MW = 1000000 W |
| Horsepower | hp | 1 hp = 745.6998716 W |
| BTU per Hour | BTU/h | 1 BTU/h = 0.2930710702 W |
Sources: NIST Special Publication 811 (power units); BTU is the International Table BTU (1,055.056 J).
Frequently Asked Questions
How many watts are in a horsepower?
1 mechanical horsepower is 745.6999 watts, or 0.7457 kW.
How do I convert kW to hp?
Multiply kilowatts by 1.34102. For example, 100 kW = 134.102 hp.
How many BTU/h is 1 kW?
1 kW is 3412.142 BTU/h.
How many BTU is a 1.5 ton AC?
A 1.5-ton air conditioner is rated at 18,000 BTU/h, about 5.275 kW of cooling.
What is the difference between kW and kWh?
A kilowatt (kW) measures power, a rate. A kilowatt-hour (kWh) measures energy used over time. Electricity bills are based on kWh.
How many watts are in a kilowatt?
There are 1,000 watts in 1 kilowatt and 1,000 kilowatts in 1 megawatt.
How many kW is a 5 kVA generator?
About 4 kW at a power factor of 0.8, because kW = kVA × power factor. The exact figure is on the generator's rating plate.
All Power Conversions
Choose a starting unit to see every conversion available from it.