HP vs BHP: Difference and Comparison

Power is defined as the capacity to do work. Its value is found by dividing the system’s energy by time.

Key Takeaways

1. HP (horsepower) is a unit of measurement for power commonly used to describe the output of engines and motors.
2. BHP (brake horsepower) is a specific measure of an engine’s power without any power losses from auxiliary components, such as the alternator or gearbox, and is determined through a controlled test.
3. Both HP and BHP are used to quantify an engine’s power output. Still, BHP provides a more accurate representation of the engine’s raw power, excluding losses from external components.

HP vs BHP

HP stands for horsepower and is a measure of the power of an engine, while BHP stands for brake horsepower and is a measure of the power of an engine at the output shaft. BHP is considered a more accurate measure of engine power, as it considers losses due to friction and other factors.

The horsepower or hp is a unit of measurement of the output power of a mechanical or electrical system. It has various types, such as metric hp and automatic hp.

The brake horsepower or bhp is the engine power of a mechanical or electrical system. It also considers the various losses due to friction in the engine.

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Comparison Table

Parameter Of Comparison	hp	bhp
Definition	HP stands for horsepower. It is the total output power of a system.	Bhp stands for the brake horsepower. It is the output power of the engine of a system.
Measured For	It is calculated for the whole system and gives the system efficiency.	It is only estimated for the system’s engine and offers the engine’s efficiency under ideal conditions.
Frictional Losses	It doesn’t take the frictional and other power losses into account.	It includes the frictional and other power losses of the system.
Measured Using	It is calculated using a simple dynamometer.	It is measured using a brake-type dynamometer.
Technique for Measurement	The dynamometer is connected to the engine, and a torque converter is used.	A brake is applied to the flywheel, and the intensity of this brake determines the bhp.

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What is HP?

The horsepower is the unit of measurement of the output power of a system. It is represented by hp and is an auxiliary unit.

The following formula is used for the measurement of horsepower :

P[hp] = ( τ[ft. lbf] × N[rpm] ) /5252

Here, τ is the torque, and N is the speed of revolution of the engine.

A dynamometer and a torque converter are connected to the machine to measure an engine’s horsepower.

1. The mechanical horsepower is represented by hp[l]. It is equal to 76.04 kg. m/s or 550 ft-lbf/s.
2. The metric horsepower is represented by hp[M]. It is equal to 75 kgf. m/s or 542.47604 ft-lbf/s.
3. The Electrical horsepower is represented by hp[E]. It is equal to 746W.

 

What is BHP?

The brake horsepower is the amount of power output by the engine. It is represented by bhp.

The measurement of brake horsepower is carried out under controlled conditions in a laboratory—the measurement is done on either the crankshaft or the system’s wheels.

The brake horsepower is always higher than the horsepower.1bph equals 1.013869 hp.

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Main Differences Between HP and BHP

Horsepower is an auxiliary functional unit for measuring large amounts of power. It is different from brake horsepower.

The main differences between the two are :

1. The horsepower hp is the output power of a mechanical or electrical system, whereas the brake horsepower bhp is the output power of the engine.
2. The hp is measured to determine the entire system’s efficiency, whereas the bhp is calculated to determine the engine’s efficiency only.
3. The hp doesn’t include the power losses in the form of friction. On the other hand, bhp inc consists of frictional losses too.
4. The hp is measured using a simple dynamometer, whereas the bhp is calculated using a brake-type dynamometer.
5. The hp is less as the losses are subtracted from it, whereas the bhp is higher as it includes the losses also.

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References

1. https://www.sae.org/publications/technical-papers/content/770465/
2. https://journals.sagepub.com/doi/pdf/10.1243/PIME_PROC_1924_106_024_02

Last Updated : 11 June, 2023