What is the difference between HP and CV?

When browsing automotive magazines or a car manual, you may come across the expression “horsepower” to refer to power values. But if this car is not national, this information can be called “horsepower”, also referring to power. In these cases, many users may be lost or have doubts about what this information really means. Other people think that these two forms of measurement are the same, but not quite.

At first, saying that the “horsepower” is used to express power mechanics, may seem absurd. However, this term was created in a historical context in which people had for the first time something other than animal traction to carry out their activities. That was when James Watt built a steam engine, and to quantify the power of work, or the work performance of this machine, he used horses for comparison, which were the source of animal traction used at the time. He observed the performance of horses that worked in coal mines, and the numbers worked. If we could measure the performance of a horse on a treadmill, it would be 745.7 watts of power, which is 1 HP.

Motor plate data.


In electricity, both HP and CV are used to express the power of electric motors, both are units of mechanical power that to be correctly used in electrical calculations need to be converted to electrical power.

Contrary to what many people think, HP (horse-power) is not simply a translation of CV (horsepower). In a national motorcycle, for example, the power usually comes in CV, but in an imported motorcycle the power can be expressed in HP. The two forms are different measures, although they represent the same magnitude. In the International System, the union that represents the power is the Watt (W), but due to divergences in the unit systems of the countries of origin the power can be expressed in HP or CV.

To facilitate the interpretation of the plate data of machines and motors we have:

1 CV = 735.5 W and 1 HP = 745.7 W

That is: 1 CV = 0.9863 HP and 1 HP = 1.0139 CV.

Quite similar, mainly in numerical comparison. A 50 HP motorcycle has 50.6 hp.

In this context, the use of HP and CV units will be used for the quantification and mechanical projection of machines that work with motors, and for the quantification of the electrical system, a conversion to the electrical power unit is necessary.

In electric motors, it is quite common to imagine that the mechanical power expressed in HP or CV would have a direct relationship with the rotation speed of the motor and this statement is false, the rotation characteristics of an electric motor are associated with other characteristics of the motor such as a number of poles and or the frequency of the electrical network (for motors connected to alternating current). The amount of mechanical power is mainly associated with the torque that an engine can exert.

Understanding this quantity and converting units is very important in the study of electric motors and even combustion engines.