Clearing Up the Confusion of Power Outputs BHP, PS and kW

Published Date: 27th Jan 2016

All manufacturers sometimes quote the power outputs of their engines using different units. This can be frustrating when trying to compare the pros of one new car or another.

So first up is BHP or Brake Horse Power. This is the most widely used unit of measure. BHP is measured at the road wheels and measures the power left over from the engine after the other loads have used some of the power like the gearbox and alternator etc. This differs to traditional HP or horsepower which is the total engine output measured at the flywheel.

Next is PS or Pferdestärke (Horse strength in German) this was replaced as the EU’s legal measurement of engine power by KW in 1992. The difference between PS and BHP is marginal with one PS being 98.6% of a BHP. It is also referred to as metric horsepower. For example, 150 PS is equivalent to 147.9 BHP, typically you would see the BHP rounded up to 148 BHP in this example.

Kilowatts or kW is sometimes used by the European manufacturers as this is the EU’s standard of measurement. A kilowatt of engine power equates to around 1.34BHP.

Torque of the engine is also measured. This is the turning power of the engine or how hard it can push you forward. Generally a diesel engine will have more torque than a petrol engine due to the longer stroke of the piston and the compression involved to ignite diesel fuel generates more turning power. Also the type of engine can have a factor on the torque produced. A V type (example V8) engine or boxer engine will produce more torque than a typical straight configuration. This is because in a V or boxer engine the pistons are firing down on both sides of the crankshaft producing more turning power or torque.  Torque is measured in Nm (Newton metres) or ft lb (foot pound) with 1 Nm being 0.737 ft lb of torque.