Watts, Kilowatts and Horsepower — Power Units Explained
What's the difference between watts, kilowatts and horsepower? This guide explains power units clearly, shows how to convert between them, and gives real-world examples.
What is Power?
In physics, power is the rate at which energy is transferred or converted. A light bulb converts electrical energy into light and heat. An engine converts fuel energy into mechanical motion. Power measures how fast that conversion happens. The higher the power, the more energy is used or produced per second.
The Main Units of Power
Watt (W)
The watt is the SI (international standard) unit of power. One watt equals one joule of energy transferred per second. It was named after Scottish engineer James Watt, who made major improvements to the steam engine in the 18th century. Most electrical appliances are rated in watts.
Kilowatt (kW)
One kilowatt equals 1,000 watts. Kilowatts are used for larger devices — electric vehicle motors, home heating systems, industrial machinery. Your electricity bill is calculated in kilowatt-hours (kWh), which is the energy used by a 1 kW device running for one hour.
Horsepower (hp)
Horsepower is an older unit still widely used for engines, motors, and vehicles. There are actually several different definitions of horsepower, but the most common is mechanical horsepower:
1 horsepower (hp) = 745.7 watts
Conversion Formulas
| Convert From | Convert To | Formula |
|---|---|---|
| Watts | Kilowatts | ÷ 1,000 |
| Kilowatts | Watts | × 1,000 |
| Horsepower | Watts | × 745.7 |
| Watts | Horsepower | ÷ 745.7 |
| Horsepower | Kilowatts | × 0.7457 |
| Kilowatts | Horsepower | × 1.341 |
Real-World Power Examples
- LED light bulb: 8–15 W
- Laptop computer: 45–100 W
- Microwave oven: 700–1,200 W (0.7–1.2 kW)
- Electric kettle: 2,000–3,000 W (2–3 kW)
- Average home: 1–5 kW average consumption
- Family car engine: 100–200 hp (75–150 kW)
- Electric vehicle motor: 150–300 kW (200–400 hp)
- Commercial wind turbine: 2–5 MW (2,000–5,000 kW)
Understanding Your Electricity Bill
Electricity is billed in kilowatt-hours (kWh). If you run a 2 kW electric heater for 3 hours, it uses 2 × 3 = 6 kWh of electricity. Multiply that by your electricity rate (e.g. $0.15/kWh) to find the cost: 6 × $0.15 = $0.90.
Convert Power Units Instantly
Use our free power converter to convert between watts, kilowatts, megawatts, horsepower, and more.