What's the difference between watts and kilowatts?

1 kilowatt (kW) = 1,000 watts (W). Watts measure smaller power outputs (light bulbs, laptops), while kilowatts measure larger outputs (appliances, motors). For example: A 60W light bulb = 0.06 kW, while a 2,000W microwave = 2 kW.

How do I convert BTU/h to watts?

Formula: Watts = BTU/h × 0.293071. For example: A 12,000 BTU/h air conditioner = 3,517 watts (3.52 kW). BTU/h (British Thermal Units per hour) is commonly used for HVAC systems in the U.S., while watts are used globally.

Why are car engines rated in horsepower?

Horsepower (HP) is a traditional unit that originated from comparing steam engines to the work done by horses. It's still used in the automotive industry for historical reasons and consumer familiarity. 1 HP = the power needed to lift 550 pounds one foot in one second. Electric vehicles often use kilowatts (kW) instead.

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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."

Formula verified against standard references

⚠️ 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.

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