About

Engineers and technicians often face a fragmentation of units between mechanical systems and electrical output. In automotive tuning, the distinction between Imperial Horsepower (used in the US/UK) and Metric Horsepower (PS/CV, used in Europe/Asia) is frequently overlooked, leading to dyno calibration errors. One HP (Imperial) equals 0.7457 kW, whereas one PS equals 0.7355 kW. This 1.4% discrepancy becomes significant in high-performance applications.

In HVAC systems, sizing air conditioners requires translating thermal capacity into electrical load. Converting BTU/hr or Tons of Refrigeration into Kilowatts allows for accurate breaker sizing and energy consumption analysis. This tool separates these domains to prevent unit pollution, ensuring you select the correct standard for your specific application.

Formulas

The conversion to Kilowatts uses linear scaling factors depending on the source unit P_src.

P_kW = P_src × C

Where C is the conversion constant. For specific automotive scenarios:

1 HP ≈ 1.01387 PS

For HVAC thermal load calculations:

1 RT = 12,000 BTU/h ≡ 3.517 kW

Reference Data

Unit Name	Symbol	Value in kW	Domain
Kilowatt	kW	1.0	Electrical
Horsepower (Imperial)	hp (I)	0.74569987	Automotive (US/UK)
Horsepower (Metric)	hp (M) / PS	0.73549875	Automotive (EU/Asia)
Electrical Horsepower	hp (E)	0.746	Motors
Ton of Refrigeration	RT	3.5168525	HVAC
BTU per Hour	BTU/h	0.00029307	Heating/Cooling
Foot-pound per second	ft⋅lb/s	0.00135582	Mechanics
Joule per second	J/s	0.001	Physics
Kilocalorie per hour	kcal/h	0.00116222	Thermal
Erg per second	erg/s	1.0 × 10^-10	Physics

Frequently Asked Questions

Imperial HP is based on lifting 550 pounds by 1 foot in 1 second. Metric HP (Pferdestärke or PS) is based on lifting 75 kilograms by 1 meter in 1 second. Because of gravity differences and unit definitions, they are not identical.

It converts thermal capability (cooling/heating power). To find the electrical consumption of the AC unit, you must divide this result by the unit's EER (Energy Efficiency Ratio) or COP (Coefficient of Performance).

HP(I) is mechanical horsepower (0.7457 kW). HP(E) is electrical horsepower used for electric motors, defined exactly as 746 Watts (0.746 kW).

Yes. Boilers often rated in Boiler Horsepower (BHP) or BTUs can be converted here. Note that 1 BHP is approximately 9.81 kW, which is significantly larger than standard mechanical HP.