A guide to car power outputs
When reading about any car, including a potential purchase, you may come across different kinds of unit measurements for the engine power output.
Depending where exactly you’re looking, the engine power may be often measured in ‘bhp’, but this is not the only unit used by manufacturers and motoring magazines. Other possible measurement units include ‘PS’, ‘hp’ or ‘kW’.
Importantly, these different measurements each result in a different calculation for the measure of engine power. This can get confusing for car buyers, when trying to compare two different models which are quoted with different power output measurements.
Here’s our guide to what each different power output commonly used for cars and vans mean.
What is bhp?
The term bhp stands for brake horsepower and it is one of the most widely used measures of engine power. Certain manufacturers including Kia and Peugeot use this power measurement for their latest cars on sale.
Brake horsepower refers to the engine’s total output remaining after taking into account the various parts which require engine power. These parts, including the likes of the gearbox, alternator and water pump, all take up a certain amount of an engine’s true total power output.
The bhp figure is therefore measured at the road wheels, outlining how much power the driver actually has access to.
What is PS?
PS is short for the word ‘Pferdestarke’, which is Germany’s word for horsepower. This measurement was actually replaced as the EU’s ‘legal measurement’ of engine power back in 1992.
Despite this change, PS is still commonly used by a lot of manufacturers selling cars in the UK market.
There is a small but significant difference in the figures shown when measuring engine power in bhp or PS.
Unlike bhp, the power output measured by PS does not subtract the energy lost when the engine has to operate parts like the gearbox and alternator. Therefore the PS figure is always higher compared to bhp.
One bhp is about 98.6 per cent of a single PS unit – so if a car’s engine produces 100PS then this translates to nearly 99bhp.
What is hp?
Using hp as the measurement of engine power is currently used by certain manufacturers such as Alfa Romeo and Fiat. This is essentially another translation for the measurement Pferdestarke or PS. The output figure shown for hp is the same as that shown for PS.
What is kW?
Measuring engine power in kilowatts or KW is sometimes used by certain manufacturers and websites, but this is far less common compared to bhp or PS.
Nowadays, the kW measurement is most likely to be used by manufacturers when referring to an all-electric or hybrid vehicle.
The power output of an electric motor is often measured with kW, although a lot of motoring websites will translate this into a bhp/PS figure.
One kW is about 73.6 per cent of a single PS unit – so a car with a total power output of 100PS works out in kilowatts to just under 74kW.
How can I convert different power outputs?
If you ever want to work out a vehicle’s power output figure into a different type of measurement, then you can use the percentage differences mentioned above as guidance.
Alternatively, certain websites such as Which? for example also provide online power converters for quick and simple calculations covering different units.