If you turn on the lights of a car, is there extra petrol or diesel consumption?

Answer

Indeed, all electrical and electronic equipment in your car initially draws its energy from the battery, including the lights, although this is usually much less than, for example, a car. the starter motor.

A battery naturally contains a limited amount of energy, and must be recharged over time using the alternator. That alternator is in turn powered by the engine of the car. If the alternator supplies power to the battery, the torque to be supplied by the engine is greater, it must supply more energy and therefore consumes more than if this were not the case.

How much more depends on the efficiency of the energy conversion of the chemical energy stored in the petrol via the engine, the alternator to the battery and the luminous efficiency of the lamps themselves. With all the heat losses in this chain of conversions, the energy consumption in equivalent fuel energy is in any case considerably higher than the light energy supplied by your headlights, even if you use the energy-saving LED versions that are gaining popularity nowadays.

I leave an exact calculation of this to more specialized insiders, but this is already a first answer.

Until further notice, the second law of thermodynamics is still in effect… 😉