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Headlights and Battery Consumption

hcdavis3

HCD3
Supporting Member
Mar 3, 2019
2,413
1,621
02571
I'm wondering if I would get any extra miles on a long trip if I made sure the headlights and fog lights were both off during the day. I know LED lights don't use a lot of power, but I'm still curious if I might get a few extra miles by keeping the lights off during the day on a long trip.
I believe the headlights are powered by your 12 volt battery. If I’m wrong I wouldn’t think leaving them off during the day would make any difference in you range.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,851
9,882
Boise, ID
@Shelburne I've seen people ask about this a few times, asking about headlights or windshield wipers or stereo volume affecting range, and they just don't. So I've made kind of a ranked list of what things make an impact and how much. Here's a link to one of my comments talking about it:

And here's another one:
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
11,702
15,179
San Diego
I'm wondering if I would get any extra miles on a long trip if I made sure the headlights and fog lights were both off during the day. I know LED lights don't use a lot of power, but I'm still curious if I might get a few extra miles by keeping the lights off during the day on a long trip.

Agreed with all of the above; don't worry about it. The impact will depend on your average speed, of course (if you travel faster you don't have to have them on as long, so you'll consume less energy per mile).

To put some numbers to it, a quick Google search for LED headlights indicates 15-45 watts consumption. I'll pick 30W. Seems reasonable when considering how bright a 15W standard issue house LED lamp is. These lights are a few thousand lumens (probably 3000-4000?), and 100 lumens per watt seems about right for "good" LED efficiency.

So, 60W for two headlights. The fog lights are going to be lower of course, I'd guess maybe 20W total.

So 80W total.

20mph avg speed: 80W/20mph = 4Wh/mi

40mph avg speed: 80W/40mph = 2Wh/mi

60mph avg speed: 80/60mph = 1.33Wh/mi

So not a huge impact!
 
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I'm wondering if I would get any extra miles on a long trip if I made sure the headlights and fog lights were both off during the day. I know LED lights don't use a lot of power, but I'm still curious if I might get a few extra miles by keeping the lights off during the day on a long trip.

bjorn tested it before with scanmy tesla. the dipped beams dont use much at all, the full beams a bit more.

But the reality of the situation is that you should use full beams if you can as visibility will trump any tiny bit of range you might gain.

The fog lights arent really up to debate. Dont switch them on when visibility is good - you will just dazzle other road users and cause an accident if you arent careful. If there is dense fog or rain you must switch them on - they make a huge difference and prevent cars from crashing into you. They are not for decoration.
I thought US spec teslas dont come with foglights anyway? I.e. I only have one rear reverse light because the other reverse light spot has been replaced with a rear foglight on the EU spec 3?
 

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