Power Converter
Convert between watts, kilowatts, horsepower, BTU/hr, and more.
Power measures how quickly energy is transferred or converted — it's energy per unit time. Watts, kilowatts, horsepower, and BTU/hr are the units you'll encounter most often, spanning home electricity, vehicle engines, and industrial equipment. Understanding power conversions helps you compare appliances, size electrical systems, and decode the specifications on motors and engines.
Popular Power Conversions
Standards Note: Horsepower Maps Back to Watts
NIST converts mechanical horsepower to 745.6999 watts, which is why a 100 hp engine or motor is roughly 74.6 kilowatts.
Watts and Kilowatts: The Electrical Standard
The watt (W) is the SI unit of power, equal to one joule per second. James Watt, the Scottish engineer who improved the steam engine, inspired the unit's name. In household electricity, watts measure the instantaneous power draw of appliances. A typical smartphone charger uses 5–20 W; a laptop uses 30–90 W; a desktop PC can use 200–600 W; an electric stovetop burner at full power uses about 2,000 W (2 kW). Your electricity bill is charged in kilowatt-hours, so a 2 kW burner running for 30 minutes uses 1 kWh.
Horsepower: The Automotive Standard
Horsepower (hp) originated when James Watt compared his steam engine's output to the work a horse could do. He estimated a horse could lift 33,000 foot-pounds per minute, which became the definition of 1 mechanical horsepower (hp) — equal to approximately 745.7 watts. A compact car engine typically produces 100–150 hp (74–112 kW); a performance sports car might produce 400–700 hp (298–522 kW). Electric vehicle motors are often rated in kilowatts by the manufacturer, but marketing materials usually convert to horsepower for US audiences.
| Unit | Equivalent |
|---|---|
| 1 hp (mechanical) | 745.7 W / 0.7457 kW |
| 1 kW | 1.341 hp |
| 1 MW (megawatt) | 1,000 kW / 1,341 hp |
| 1 BTU/hr | 0.293 W |
| 1 ton (cooling) | 12,000 BTU/hr / 3,517 W |
| 1 watt | 1 J/s = 3.412 BTU/hr |
Power in Renewable Energy
Solar panels are rated in peak watts (Wp) — the power output under ideal conditions. A typical residential solar installation of 6 kW (peak) generates roughly 7,500–10,000 kWh per year, depending on location and shading. Wind turbines are rated in megawatts (MW): a modern offshore turbine produces 10–15 MW. Power plants are measured in gigawatts (GW); the US total generating capacity is about 1,100 GW. Understanding these unit relationships helps interpret energy news, evaluate solar installation proposals, and compare renewable energy options.
What Is Horsepower & Why It's A Dumb Unit - America vs Metric | Engineering Explained
Engineering Explained puts horsepower into modern metric context, which helps readers understand why watts, kilowatts, and horsepower all appear on the same spec sheet.
Video source: Engineering Explained
Further Reading
Sources & References
- NIST — Units and Conversion Factors — Power unit conversions (watts, horsepower) from NIST.