Power. Perhaps the most striking feature in a car. Traditionally we have measured it in horsepower (CV), although in other countries horsepower (hp) and brake power (bhp) are used, the latter two especially in Anglo-Saxon countries. And although they have similar values, they are all different. Fortunately, there is a unit derived from the International System to measure power and which is gaining popularity with electric cars: the kilowatt.
By international convention of the scientific community, 1 meter measures the same here in Spain, in Indonesia and on the surface of the Moon; 1 second lasts the same in all the confines of the planet; and the same goes for kilos and mass. The world agreed to use universal units of measure and although it may seem like a trifle, it was a very important advance. Although the Anglo-Saxons use the inch, the foot and the gallon in their daily lives, at NASA they do the calculations with meters, kilometers and liters.
So if we have universal units to measure any magnitude, why do we still use multiple power units? It is a good question whose answer will influence, from now on, electric cars. With them, the kilowatt (kW) is beginning to be used to a greater extent to talk about its power due to the historical relationship of this unit with electromagnetism. So let’s get to know the kilowatt a little better, its definition and its equivalence in horsepower.
What is a kilowatt?
The kilowatt is a multiple of the watt or watt (symbol: W), which is a unit derived from the International System of Units for measuring power. One watt is equal to 1 joule per second (1 J/s), that is, the power equivalent to doing 1 joule of work in 1 second.
Taken to the field of electromagnetism, a watt is the amount of work done per unit of time when a current of 1 ampere (A) circulates with a potential difference of 1 volt (V). It can also be defined as the heat power radiated by a resistance of one ohm through which one ampere circulates.
The watt, which is the Castilianization of watt, named after James Watta Scottish engineer and chemist who in the eighteenth century contributed fundamentally to the development of the steam engine and, therefore, to the Industrial Revolution and the development of the United Kingdom first and the rest of the world later.
One kilowatt (kW) is equal to 1,000 watts (W). Due to the magnitude of the power of current engines, the kilowatt is used for greater comfort of use.
How many hp is one kW equal to? How to convert kW to hp?
Now we know the definition of watt and kilowatt, but how many horsepower (hp) does 1 kW equal? The answer is simple: rounding off, 1 kW equals 1.36 hp. To know the power of a car (or any other machine) in horsepower, just multiply the kilowatts of the engine by 1.36; the result is CVs.
- 1 kW = 1.359 CV (in practice it is rounded to 1.36)
- 1 CV = 0.7353 kW (in practice it is rounded to 0.74)
Therefore, a motor of 100 kW of power has 136 CV. Some electric cars have two electric motors or more; in some of these cases, the total power can exceed 736 kW, which is 1,000 of the traditional horsepower.
And inversely, a 100 hp motor has 74 kW. In electric cars it is rare to see such low figures (due to the ease with which a lot of power can be achieved with a relatively small electric motor).
Why we should always use the kilowatt (kW) to measure power
Interestingly, power has been expressed in kilowatts for decades on car data sheets. However, in everyday life we are still mostly using horsepower. I guess for a simple matter of familiarization with that unit.
The popularization of the electric car is causing more and more talk in kilowatts to quantify the power, both to talk about the motors and for the recharging power. And this should definitely lead to the widespread adoption and use of the kilowatt as a universal power unit, whether in electric cars or in cars with combustion engines.
It is not only more practical, but also more logical: 1 kilowatt is defined the same for Europeans as it is for Americans, Asians and the British. Just as we use universal units of the International System such as the meter, the second or the ampere to measure distances, time or electric current, we should apply the same criteria with power and use the kilowatt also in everyday life. The age of the steam engine is long gone; It’s time to talk about power in kilowatts.