How many watts is 1 horsepower?

It depends on the type: mechanical (imperial) horsepower = 745.7 W; metric horsepower (PS/CV) = 735.499 W; electrical horsepower = 746 W exactly. Car ratings in the US use mechanical hp; most European ratings use metric hp (PS).

How do I convert kW to BTU/h?

1 kW = 3,412.14 BTU/h. Multiply kilowatts by 3,412.14 to get BTU/h. This conversion is common for HVAC system sizing.

What is the difference between mechanical and metric horsepower?

Mechanical horsepower (used in the US) = 745.7 W. Metric horsepower (PS, used in Europe) = 735.5 W. They are close but not equal - a 200 PS engine is about 197 mechanical hp.

What does BTU/h measure?

BTU per hour (BTU/h) measures the rate of heat energy transfer, commonly used for air conditioners and furnaces. 1 BTU/h ≈ 0.293 W. A 12,000 BTU/h air conditioner is about 3.52 kW.

Power Converter - Toolcroft

Common power conversions

Value	Equivalent
1 hp (mech)	745.7 W = 0.7457 kW
1 hp (metric/PS)	735.5 W = 0.7355 kW
1 hp (electrical)	746 W = 0.746 kW
1 kW	1.341 hp (mech) = 3,412 BTU/h
100 kW	134.1 hp (mech)
1 MW	1,000 kW = 1,341 hp
1 BTU/h	0.2931 W
12,000 BTU/h	3.517 kW (1 ton of A/C)

How power conversion works

All conversions use Watts as the base SI unit. The three horsepower variants are not identical: mechanical hp (745.7 W) is the standard US definition; metric hp (PS, 735.499 W) is used in Europe; electrical hp (746 W exactly) is used for electric motors per IEEE standards.

Power vs energy

Power measures the rate of energy transfer (joules per second = watts). Energy is power multiplied by time: 1 kWh = 1 kW × 1 hour = 3,600,000 J. Use the Energy Converter for energy unit conversions.

Real-world power reference

Device / Application	Typical power
LED light bulb	9 W
Laptop (charging)	45 W
Desktop PC (gaming)	200–600 W
Microwave oven	1,000 W (1 kW)
Electric water heater	4,500 W (4.5 kW)
EV Level 2 charger (home)	7,200 W (7.2 kW)
Central air conditioner (3-ton)	3,500 W (3.5 kW)
Tesla Model 3 motor (peak)	239,000 W (239 kW ≈ 320 hp)

Three-phase power note

In industrial and commercial settings, three-phase AC power is standard. The apparent power formula is:

S = √3 × V_line × I × PF

Where S is apparent power (in VA or kVA), V_line is the line-to-line voltage (e.g., 480 V), I is current per phase, and PF is power factor (typically 0.8–0.95 for industrial loads). The distinction between kVA (apparent power) and kW (real power) matters for generator sizing and utility billing.