Quick answer: Power is the rate of energy transfer, measured in watts: one watt equals one joule per second. Electrical power is voltage times current. Common conversions: one kilowatt is 1000 watts, one mechanical horsepower is 746 watts, and one BTU per hour is about 0.293 watts. Match the unit to motors, appliances or heating specs.
Last reviewed: September 2026
Key facts
- 1 mechanical hp = 745.7 W; 1 kW = 1.341 hp.
- 100 hp = 74.57 kW — a typical family car engine.
- Metric horsepower is slightly smaller: 735.5 W.
- 1 BTU/h = 0.293 W — the unit on air conditioners.
Car brochures quote horsepower, EV specs quote kilowatts, air conditioners quote BTU/h — three units for the same thing: the rate of doing work. This free power converter translates between watts, kilowatts, megawatts, mechanical and metric horsepower, and BTU per hour instantly.
Enter a value and choose your units. Remember: power is the rate (kW); energy is the amount (kWh) — the converter’s companion Energy Converter handles that side.
How to use
- Enter a value.
- Choose the from and to units.
- Read the answer and the full table of equivalents below.
How power conversion works
| Term | Meaning |
|---|---|
| from-unit in watts | Each unit’s exact definition in watts. |
| to-unit in watts | The target unit’s definition in watts. |
Power = energy ÷ time: 1 watt = 1 joule per second. An appliance’s wattage times its running hours gives the kWh on your bill.
Worked examples
Car engines
100 hp → kW: 100 × 0.7457 = 74.57 kW.
150 kW EV → hp: 150 × 1.34102 = 201.15 hp — why electric cars quote both figures.
Home appliances
2 kW heater → hp: 2 × 1.34102 = 2.68 hp.
12,000 BTU/h air conditioner → kW: 12,000 × 0.000293071 = 3.52 kW of cooling — a “1-ton” AC unit.
Power units in watts
| Unit | Equals (W) | You meet it in |
|---|---|---|
| Watt (W) | 1 | Bulbs, chargers, SI base |
| Kilowatt (kW) | 1,000 | EVs, home circuits |
| Megawatt (MW) | 1,000,000 | Power stations, wind farms |
| Horsepower, mechanical (hp) | 745.7 | US/UK car engines |
| Horsepower, metric (PS) | 735.499 | European car engines |
| BTU per hour | 0.293071 | Air conditioners, heaters |
Frequently asked questions
How do I convert hp to kW?
Multiply mechanical hp by 0.7457: 100 hp = 74.57 kW. For metric hp (PS), multiply by 0.7355.
What is the difference between metric and mechanical horsepower?
Mechanical (imperial) hp = 745.7 W; metric hp (PS, “Pferdestärke”) = 735.5 W. They differ by about 1.4% — European cars usually quote PS.
kW vs kWh — which is which?
kW is power: the rate energy flows. kWh is energy: power × time. A 2 kW heater running 3 hours consumes 6 kWh.
What does BTU/h mean on an air conditioner?
Cooling capacity per hour. 12,000 BTU/h (≈ 3.5 kW) is the classic “one ton” of cooling for a medium room.
How much power does a house use?
A typical home draws 1–3 kW on average, peaking at 5–10 kW with heating or cooking — check your smart meter.
Sources
Key takeaways
- 1 hp = 745.7 W; 1 kW = 1.341 hp; 1 BTU/h = 0.293 W.
- Metric hp (735.5 W) and mechanical hp (745.7 W) differ — check which a spec means.
- Power (kW) × time = energy (kWh): the two converters are a pair.
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