Does charing your cell phone affect gas mileage?

hybrid-repair
gasoline
fuel-economy

#1

Let me start by saying I know that if the answer is yes, it’s infinitesimal. But here’s the question:



When I plug my cell phone, GPS, etc. into my cigarette lighter to charge, does it draw energy from the engine that is not being generated anyway? Or does the car continuously generate that energy for the lighter, and it goes to waste when nothing is plugged in? And does it make any difference if you’re in a hybrid vs. a conventional car?


#2

Yes, but it’s infintesimal. Well done!

The alternator works “on-demand”, so as there’s more draw placed on your car’s electrical system (i.e. more electrical stuff being used), it gets harder to turn and therefore the engine uses more energy to turn it. So plugging in your electrical device makes it take some incredibly small and unmeasurable amount more of energy to turn the alternator.

A hybrid still has a 12v electrical system that runs all of the “normal car” stuff such as the headlights, computer, cigarette lighter, etc. that’s totally seperate from the generator and batteries that run the traction motor. So it’s a similar situation.


#3

Yep, on the Geo Metro that I owned, you could actually detect a slight change in engine idle speed when the headlights were switched on and off with a fully charged battery.


#4

With modern engines the PCM will compensate and let more air into the intake if the alternator is loaded more. With a significant electrical load, you can still probably detect a dip in idle speed before compensation.


#5

Of course, if you idle the car while fiddling with the cigarette lighter plug in. . . .

Scrabbler