Power Conversions
Power
Power is the rate at which energy is transferred, converted, or consumed per unit of time. The SI unit is the watt (W), defined as one joule per second (J/s), named after the Scottish engineer James Watt, whose improvements to the steam engine in the 1760s and 1770s launched the Industrial Revolution. The relationship between power, energy, and time — Power = Energy ÷ Time — means that a 100-watt device running for one hour consumes 100 watt-hours (0.1 kWh) of energy, a figure directly reflected on electricity bills.
Horsepower (hp) is the most widely recognised non-SI unit of power, originally defined by James Watt himself as an approximation of the power output of a draft horse, used to market steam engines to farmers. The US mechanical horsepower equals 745.7 watts. The metric horsepower (PS, from the German Pferdestärke, or CV in French and Spanish) equals 735.5 watts — slightly less. This distinction matters when comparing car specifications across markets: a European car rated at 200 PS produces 147.1 kW, while a US car rated at 200 hp produces 149.1 kW — a difference of about 1.4%.
In electrical engineering and renewable energy, power is expressed in kilowatts (kW) and megawatts (MW). A typical household uses between 1 and 5 kW at any given moment; a large wind turbine generates 2–15 MW; and the largest power plants produce gigawatts (GW) of electricity. Understanding power unit conversion is essential in engineering design, energy policy, automotive specifications, and the growing field of sustainable energy systems.
Popular Comparisons
| W | kW | hp | BTU/h | |
|---|---|---|---|---|
| LED bulb | 10 | 0.01 | 0.013 | 34.1 |
| Microwave | 1,000 | 1 | 1.341 | 3,412 |
| Electric kettle | 2,000 | 2 | 2.682 | 6,824 |
| Family car engine | 120,000 | 120 | 160.9 | 409,440 |
| Sports car engine | 373,000 | 373 | 500 | 1,272,676 |
Frequently Asked Questions (FAQ)
How do I convert horsepower to kilowatts?
Multiply US mechanical horsepower (hp) by 0.7457 to get kilowatts. For example, a 200 hp engine produces 149.1 kW. Note that metric horsepower (PS or CV, used in European car specifications) uses a slightly different value: 1 PS = 0.7355 kW. A 200 PS engine therefore produces 147.1 kW — not the same as 200 US hp. Use our converter to select the correct horsepower type.
What is the difference between power and energy?
Power is the rate at which energy is transferred or converted — how fast work is done. Energy is the total amount of work done over time. The relationship is: Energy = Power × Time. A 100-watt bulb (power) running for 10 hours consumes 1,000 watt-hours or 1 kWh (energy). Power is measured in watts (W); energy is measured in joules (J) or kilowatt-hours (kWh).