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Power Converter
Understanding Power Units
Power is the rate at which work is done or energy is transferred. Different industries use different units:
- Watts (W) & Kilowatts (kW): The standard SI units used for electricity, appliances, and motors.
- Horsepower (HP): Traditionally used for engines (cars, lawnmowers) and mechanical motors.
- BTU/h: British Thermal Units per hour, commonly used in HVAC (heating and air conditioning) to measure cooling/heating capacity.
Common Conversion Formulas
| From | To | Formula |
|---|---|---|
| Horsepower (HP) | Watts (W) | HP × 745.7 = W |
| Kilowatts (kW) | Horsepower (HP) | kW × 1.341 = HP |
| BTU/h | Watts (W) | BTU/h × 0.293 = W |
💡 Expert Tip: The "746 Rule"
"When working with electric motors, remember the number 746. One electrical horsepower is defined as exactly 746 watts. However, for mechanical calculations, we often use 745.7 watts. For rough estimates in the field, thinking of 1 HP as roughly 3/4 of a kilowatt (0.75 kW) is a quick and useful shortcut."
— Robert Wilson, Electrical Engineer
⚠️ Common Mistakes
- Confusing Mechanical vs. Electrical HP — Mechanical HP (approx. 745.7 W) is used for engines. Electrical HP (746 W) is used for electric motors. Metric HP (PS) is slightly different (approx. 735.5 W).
- Mixing up Energy and Power — Power (kW) is the rate, while Energy (kWh) is the total amount used over time. Don't confuse them!
- Overlooking Efficiency — When converting motor output (HP) to electrical input (kW), you must account for efficiency. A 1 HP motor draws more than 746 watts of electricity because no motor is 100% efficient.
Frequently Asked Questions
How many watts is 1 horsepower?
1 mechanical horsepower (HP) is approximately 745.7 watts. 1 electrical horsepower is exactly 746 watts. For most general purposes, 746 W is the standard conversion.
What is the difference between kW and kWh?
kW (Kilowatt) is a unit of power (how fast energy is used). kWh (Kilowatt-hour) is a unit of energy (total amount used). Think of kW as the speed of your car, and kWh as the distance traveled.
How do I convert air conditioner BTU to Watts?
Multiply the BTU/h rating by 0.293. For example, a standard 12,000 BTU/h unit consumes approximately: 12,000 × 0.293 = 3,516 watts (or 3.5 kW) of cooling capacity.