Experiment: The cost of Headlights

[brucey]

Yeah, I forgot to note the speed, it was 55 and I've added it to the original post.

But it was a clear sunny day and there was no traffic on the road, so as many variables as I could should have been removed. I know it should be taken with a grain of salt. I do like the fact that the testing, with averages, test very similar to the theoretical side of things as well.

[brucey]

Originally Posted by RobertSmalls

Surprisingly, high beams are typically 60W, versus 55W for low beams. It's not so much that there's more light, it's mostly that it's cast further down the road. Also into oncoming drivers' eyes.

Good work, Brucey (and Pale).

Btw, what speed did you set the cruise to?

Are you sure about this? I could have sworn on my car, the high beams and the low beams were seperate bulbs. And with the high beams on, the low beams still run, adding another 110~120 watts into the equation.

[Ryland]

Marker lights tend to be 5 watts each, common to have 4 to 8 or more marker lights, not a big load but it adds up to another 20 to 40 watts, add to that the one watt light bulbs in the dash, 10 or more of those to keep everything lit.

[Weather Spotter]

Originally Posted by brucey

Are you sure about this? I could have sworn on my car, the high beams and the low beams were seperate bulbs. And with the high beams on, the low beams still run, adding another 110~120 watts into the equation.

Mine are separate bulbs too. they make a single bulb with two filaments too, so that might be the cause for the confusion.

[RobertSmalls]

Yep, the top three part numbers for high beams all use 60W per bulb. I'm accustomed to cars that turn off the low beams to run the high beams, but if yours can run both at the same time, then it will draw more power.

[camopaint0707]

great write up, i never would have guessed the difference would be that noticeable, i wonder how bad the difference is between no lights and the DRL lights

[04_Sentra]

I had to try this for myself for the sake of curiosity and since every car is different the results will be different. I checked it out in gph instead of mpg though since the headlight load is going to be constant, the same at idle as at highway speed. Once the car was completely warmed up I was using 0.2 gph at idle and when the headlights turned on it went to 0.23 gph. I repeated this several times each time waiting ~30sec to make sure it was not just a momentary change in consumption, with the same results each time. So for the Sentra the headlights/taillights use 0.03 gph. On level ground at 45mph the Sentra uses ~1gph so that's a 3% difference for lights/no lights. If I did a lot of driving at night I think that I would look into LED lights.

[Angelus359]

Use LED headlights?

[tumnasgt]

Originally Posted by 04_Sentra

I checked it out in gph instead of mpg though since the headlight load is going to be constant, the same at idle as at highway speed. Once the car was completely warmed up I was using 0.2 gph at idle and when the headlights turned on it went to 0.23 gph.

I don't think the difference will be constant, as at different loads/RPMs the engine changes efficiency (idle being pretty bad). It would be interesting to see how much different loads/RPMs change the effect.


Also, for electric load tests (as the fuel consumption change should be similar between vehicles), it makes sense to use gallons/100miles or similar, as a 3MPG loss on a 100MPG car is only 0.03 gallons wasted per 100miles, where as on a 15MPG pickup it's 1.67 gallons wasted per 100 miles. Percentages are also off for a test like this because x% of a pickup's fuel consumption is much greater than x% of a hybrid's fuel consumption.
I don't want to start a unit war, it's just food for thought.

[tumnasgt]

Originally Posted by Angelus359

Use LED headlights?

LED running lights are a viable option, but aren't all that cheap (about $50 a pair for ones that are legal to use in countries that recognize EU vehicle lighting standards). I worked out that on my mom's car it will take about a year to pay them off (20,000km a year, 0.2l/100km saving, $5.40US/gal), now I just need to convince her to get a set

LED headlights on the other hand are practically impossible to retrofit as you need a lot of cooling for really high power LEDs, so a standard headlight housing won't work.