Is wasted energy in keeping vehicle headlights on, an implication on gas consumption?

Question

Commuting on roads & highways, we see so many vehicles with the head lamps lighted. The energy required converted from engine to generator, puts some load on the engine, thus consuming more gas.

Can we improve gas consumption by turning off the lamps during day time travel? As a by product - saving the imported energy source - the petrol?

Answer 1

Yes, having the lights on increases gasoline (or diesel as the case may be) consumption slightly, but not so much that you would notice it on an individual basis.  The electricity must come from somewhere, and ultimately it is produced by burning fuel.

To those who do not think it makes a difference, because the alternator is always generating electricity, you need to do a little more research on how a car's electrical system works.  Included in the system is a little device called a voltage regulator.  This senses the charge condition of the battery and determines how much electricity must be produced.  Also, if you don't believe that turning the lights on makes a difference on the engine load, just hook up a good tachometer and then turn the lights on.  You will see a momentary drop in RPMs as the load on the alternator increases.  The engine management system then adjusts the amount of fuel going into the injectors and the air flow to compensate for this additional load and bring the engine back to the set point speed.

My car has small incandescent running lights that are always on and High Energy Discharge (HED) head lights that come on automatically when it gets dark.

Answer 2

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Answer 3

You are correct that running with your headlights on does increase your fuel consumption.

Rickounet has some very valid points.

Theoretically it does reduce accidents according to some statistics, (which makes sense because you should be more visible to other drivers) and LED lights would consume much less power for any given light intensity being produced.

I do have to chuckle a bit at redhot.....'s answer however.

He hasn't really got a grasp of basic physics, and I have no idea where he's got his information, or is just spouting off what he believes.

The facts are that:

1) It requires energy to make energy.

2) The main purpose of the vehicle's battery is for starting purposes only. once the car is started the alternator takes over. First it replenishes the discharge of the battery until it reaches full charge at 13.8 volts for a lead acid battery.

3) Any additional power drain caused by use of lights, radio, etc. is going to cause the alternator to work harder to produce this power. This power comes from the engine, and hence some loss of fuel mileage.

The percentage of fuel being consumed however will depend on how efficient your vehicle is in the first place.(My Belief)

The more efficient your vehicle is, the more effect you will notice, because an inefficiently running vehicle will mask small changes, whereas a more efficient vehicle could detect the increased load.(as minor as it may be).

The answer however to your question is basically that you could save a few pennies by not using your lights when they are unnecessary, the amount you save is questionable

Thanks for the question.

I hope this was somewhat helpful.

I see Jesse also has a bit more to learn.

Answer 4

Running the headlights will use a little bit more gas; on the order of a few gallons a year for the average driver. Having the alternator constantly generate the same amount of power and "bleed off" the extra as some have mentioned would be incredibly wasteful, so that is not how it is done.

Answer 5

Actually no. Keeping the lights on has been proven to not effect gas milage in anyway. The reason is the battery must be constantly charged no matter what you may or may not turn off such as the radio, lights or any other electrical item. Since these item run off the battery, not the generator, they do not put a load on the generator therefore, not changing the milage. Unless your battery in so bad it should be changed out anyway.

Answer 6

Sure, but it decreases the risk for accidents. And each accident costs a lot of energy (replace/repair vehicle, etc.)

"They" should only make LED headlights, that would save a lot

Answer 7

the engine is constantly turning the alternator no matter if anything electronic is on. and the alternator is constantly making the same amount of energy maybe changing a little depending on RPM so whether or not the headlights are on or not, its still gunna be using some of the power from the engine.

Answer 8

The question of importation vs consuming one's own energy is not an environmental consideration.

We do consume energy to produce light, and most cars today have no switch to turn off running lights, (We make a distinction between headlights and running lights even though the same lights are used, because the energy used is lower).

We could save more fuel by changing both running lights and headlights to LED. That is, with LED lights, we would use less than with our incandescents. And running with an LED that costs us just a watt or even less is negligible for its safety benefits.