Table of Contents
Understanding Power Units
Power is the rate at which energy is transferred or converted. Different industries and regions use different units to express power. The watt is the SI standard, but horsepower remains popular in automotive and mechanical engineering, while BTU/hr is common in HVAC applications.
Converting between these units is essential when comparing equipment specifications from different manufacturers or regions. A motor rated in horsepower needs to be compared with electrical supply in watts, and a heating system rated in BTU/hr needs to match with an electrical panel in kilowatts.
Conversion Factors
| From | To Watts (multiply by) |
|---|---|
| 1 Kilowatt (kW) | 1,000 |
| 1 Megawatt (MW) | 1,000,000 |
| 1 Horsepower (hp) | 745.7 |
| 1 BTU/hr | 0.29307 |
| 1 Calorie/sec | 4.186 |
Quick Conversion Table
| Watts | kW | hp | BTU/hr |
|---|---|---|---|
| 100 | 0.1 | 0.134 | 341.2 |
| 500 | 0.5 | 0.671 | 1,706 |
| 1,000 | 1.0 | 1.341 | 3,412 |
| 5,000 | 5.0 | 6.705 | 17,061 |
| 10,000 | 10.0 | 13.41 | 34,121 |
Practical Uses
- HVAC sizing: Convert between BTU/hr ratings and kilowatt electrical requirements.
- Automotive: Compare engine output in horsepower to generator capacity in kilowatts.
- Solar panels: Convert panel wattage to kilowatts for system design.
- Industrial: Match motor horsepower ratings to variable frequency drive kW specifications.
Frequently Asked Questions
Is mechanical horsepower the same as electrical horsepower?
No. Mechanical (imperial) horsepower equals 745.7 watts, while electrical horsepower equals exactly 746 watts. The difference is negligible for practical purposes, but metric horsepower (PS) equals 735.5 watts.
Why are there so many power units?
Different units evolved in different industries and eras. Horsepower was created by James Watt to market steam engines, BTU originated from heating engineering, and the watt became the international standard through the metric system. Each persists where tradition is strong.
How do I convert kW to kWh?
Kilowatts measure power (rate), while kilowatt-hours measure energy (total). Multiply kW by time in hours: 5 kW running for 3 hours = 15 kWh. This calculator focuses on power unit conversions only.