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HP to kW – how to convert engine power?
HP to kW – how to convert engine power?
Engine power is one of the most important parameters that shows us the capabilities of the drive unit. It is given, among others, in horsepower and kilowatts. What are the differences between these units and how to convert kW to HP? Let's check.
What is kilowatt (kW)?
Engine power is the amount of work the engine can do in a given time. It is nothing more than KM per kW. Putting it into simpler language, it shows how much torque we have at a given revolutions, i.e. how dynamic the engine will be and what acceleration it will allow. Knowledge of how the power of the drive unit is calculated will be useful, for example, when we want to buy a used car. We can often obtain information about the engine parameters by by checking the VIN number.
The most universal unit of engine power is the kilowatt, abbreviated as kW, because it belongs to the SI system. The International System of Units has been in force since 1960. It is based on the metric system, which uses units such as meters, kilograms, seconds, joules and watts (W).
The kilowatt is the official official unit. Engine power in kW is given, among others, by: in approval documents or in the registration certificate.
What is horsepower (HP)?
Although the kilowatt is a unit used by administrative authorities, vehicle manufacturers and automotive fans usually use horsepower (KM). It is simply more popular.
This unit was also in official use on our continent until the kilowatt was adopted as the official unit of power, first by the European Economic Community in 1972, and then by the European Union in the 90s. Car manufacturers willingly use horsepower, because it shows higher values compared to kilowatts and other units when engine power is given.
The horse power is a unit developed in Germany, following the example of the Anglo-Saxon steam horse, which we will come to later. This is where its alternative abbreviation PS comes from, from Pferdestärke (German for horsepower).
KM per kW – dynamometer
What are the differences between kilowatt and horsepower?
What is the actual ratio between HP and kW? Both horsepower (HP, PS) and kilowatt (kW) indicate the power of the drive unit. Therefore, they do not differ in terms of application.
However, the issue of calculating power is different. To get the value in kilowatts, you multiply torque expressed in newton meters by the engine revolutions, and divides the obtained result by the constant value resulting from the change of units (formula Nm × rpm/9549,3).
One horsepower is the power needed to lift 75 kg to a height of 1 m in one second. The formula is as follows: 1 HP = 75 kGm/s.
HP to kW converter – how to convert horsepower to kilowatts?
How to convert kilowatts to horsepower? The most important thing is to know that:
- 1 kW = 1,36 HP,
- 1 HP = 0,74 kW.
The conversion from kW to HP and vice versa is simply a product. If we know the power in kilowatts and want to get the result in horsepower, we multiply:
- value in HP × 0,74 = power in kW.
How to calculate horsepower if we know power in kW? We perform the following action:
- value in kW × 1,36 = power in HP.
Examples of converting HP to kW and kilowatts to horsepower:
- 100 HP × 0,74 = 74 kW,
- 150 HP × 0,74 = 111 kW,
- 100 kW × 1,36 = 136 HP,
- 150 kW × 1,36 = 204 HP.
KM to kW, HP and BHP – what are the differences?
In addition to the kW and HP units, HP and BHP are also used. What do these abbreviations mean? How does the conversion of kW and HP into HP and BHP look like?
HP stands for horse power. This is a formula developed by James Watt, the inventor after whom the watt power unit is named. HP was intended to compare the power of steam engines with horses. Watt created a formula based on estimates of the animal's strength (800 Nm, or 180 lbf, or pound-force) and how many times in an hour the horse would turn a 12-foot radius treadmill. The formula for a steam horse is:
- 1 HP = 550 lbf × ft/s (550 lbf × English foot/second).
HP is a unit often used in English countries. In addition, there is BHP (brake horse power). This is the power obtained on the dynamometer, after taking into account the resistance of the drive system. HP and BHP, i.e. imperial units, have a lower value compared to KM.
The KM and kW to HP converter looks like this:
- 1 HP = 0,99 HP,
- 1 kW = 1,34 HP,
- 1 HP = 1,01 HP = 0,75 kW.
Engine power can be expressed in various ways. It is good to check its value when, for example, we intend to re-register the car. If the incorrect power is entered in the ID, it may mean that the document needs to be replaced. Now you know everything about HP per kW.
