Why power is measured in horsepower rather than kW;

Have you ever wondered why the power of the car has come to be measured in horsepower and not in kW;

Before too many years the power of a machine measures with the unit that had adopted the James Watt from the late 18th century. For many decades, but as far as comparing the power of an engine in a car take the horsepower and the photograph shows us a great truth: the relationship of quads with horses much earlier than the car.

Μετά την εφεύρεση της ατμομηχανής το 1712, ο Nicholas Cugnot (Νικολά Κινιό) κατασκευάζει το 1769 ένα ατμοκίνητο όχημα με ένα τεράστιο λέβητα στο εμπρός μέρος. Η ισχύς του έφτανε μερικά kW, δεν μπορούσε άλλωστε να μετρηθεί με κάποια άλλη μονάδα μέτρησης. Ωστόσο, η ταχύτητα μίας άμαξας και η μεταφορική της ικανότητα μπορούσε να γίνει αντιληπτή μόνο από τον αριθμό και την ράτσα των ίππων. Μέσα από την σχέση των ιππήλατων αμαξών καθιερώθηκε ο ορισμός της ιπποδύναμης, της ελκτικής δύναμης που ασκούσαν τα άλογα για να τραβήξουν την άμαξα. Βέβαια, στο αυτοκίνητο δεν υπάρχει αυτή η ελκτική δύναμη αλλά η ροπή του κινητήρα για την οποία έχουμε μιλήσει στο σχετικό άρθρο.

After the invention of the steam engine in 1712, the Nicholas Cugnot (Nicolas Kugnot) manufactures in 1769 a steam-powered vehicle with a huge boiler front. The power reached some kW, could also be measured by some other unit of measurement. However, the speed of a trolley and carrying capacity could be understood only by the number and breed of horses. Through the relationship of horse-drawn carriages established the definition of horsepower, the pulling force exerted by horses to pull the wagon. Of course, the car does not have this pulling power but the torque of the engine for which we have spoken in the relevant article.

For engineers, students and experts of automotive industry is much more understandable to talk about the power of using the unit kW (1 metric horse (PS) = 0,736 kW and an English one horsepower (HP) = 0,746 kW)). Something that is even more utilitarian talking about electric cars. Here be remembered that the power (P) is the work (W) produced per unit of time (t) as defined by the relationship P = W / t.

On the other hand, ordinary people, the brochures, ads on TV etc. usually refer to the horsepower of a car which has established itself almost since the introduction of the International System of Units SI (MKS or Meter, Kilogram, Second). Almost all references to the power of a car talking about horses or horse-and not kW. Of course, this could be a simple conversion (kw = PS / 0,745 or PS = kw * 1,359) but a lot of people trouble as yardstick kW accustomed to PS.

On the other hand, is remarkable is that directive EE (80/181/EEC, 1-2010) a requirement of maximum usable power in kW (such as registration) and supplementary in horses. Things start to get confused even more with electric cars whose power given in kW influencing the psychological factor due to the smaller number of unit (in a few days we will talk about the difference between kW and kWh).

To conclude, what you have on the matter? Prefer to talk about the power of a car in horsepower or kW; Which unit do you think is appropriate for an electric car?