Do electical accessories affect MPG?
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Tuned
Joined: Aug 2005
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From: Brew City, USA New Berlin
Do electical accessories affect MPG?
Hopefully this isn't a dumb question...
Do electircal accessories affect your gas mileage?
My hunch was that the alternator runs all the time so pulling electricity off for accessories shouldn't affect mpg.
But I couldn't help but wonder. For example if I have my heated seats on, does that have any affect on gas mileage?
Do electircal accessories affect your gas mileage?
My hunch was that the alternator runs all the time so pulling electricity off for accessories shouldn't affect mpg.
But I couldn't help but wonder. For example if I have my heated seats on, does that have any affect on gas mileage?
Senior User
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Yes, technically any electrical load will effect gas millage. Even though the alternator is always turning and likely always has some load on it, the more power it supplys, the harder the pully will be to turn on the alternator and therefore a load on your engine that will affect gas millage. In the real world I don't know if you would ever notice the difference. John
Posting Guru
Joined: Mar 2005
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From: Burnsville, MN
Well, actually, yes. Other than your starter, which is only used intermittently, your lights can be a nontrivial load. So during operations at night, the wattage for powering your lights has to come from somewhere, and that's the engine.
Yes, the alternator turns whether the lights are on or not, but when on, the alternator's field coil is energize to create a greater resistance to the motor. Now with a PSD it might not make much difference, but in a car, I've always heard that it costs you a mile or two, though I've never worked it out.
Yes, the alternator turns whether the lights are on or not, but when on, the alternator's field coil is energize to create a greater resistance to the motor. Now with a PSD it might not make much difference, but in a car, I've always heard that it costs you a mile or two, though I've never worked it out.
Elder User
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From: Putnam Valley, New York
Gas Mileage
Anything that draws current makes the alternator harder for the engine to turn. The more the load, the more effort is required from the engine. Light loads like the dome lamp or radio have little effect, but heavy loads like the headlamps, hi speed blower, or heated seats will definately affect your gas mileage--maybe not by much, but some.
RON
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Look at it this way. 746 watts equals one horsepower. The output voltage of the alt is about 14.5 volts. That means that you would have to have a current draw of 51.4 amps to be losing one horsepower. So if you put a big load on the power supply you will have to use more fuel to take care of it. But you can also look at it that if running unloaded that it takes 100 HP (I just picked a number) that a 50 amp load would take add 1% more power so it should be very little extra fuel.
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Cargo Master
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From: Friendswood, Texas
Originally Posted by Aarkie
Look at it this way. 746 watts equals one horsepower. The output voltage of the alt is about 14.5 volts. That means that you would have to have a current draw of 51.4 amps to be losing one horsepower. So if you put a big load on the power supply you will have to use more fuel to take care of it. But you can also look at it that if running unloaded that it takes 100 HP (I just picked a number) that a 50 amp load would take add 1% more power so it should be very little extra fuel.
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Fleet Owner
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From: Brentwood,CA
but also realize how easy it is to draw 52 amps.
the heater motor draws 15 amps, headlights 15 to 20, heated seats 20 amps each, then you have the drwa of the engine and its systems. which add up to a constant 20 amps all the time of power use. so 90 amps. but still not a lot of HP loss
the heater motor draws 15 amps, headlights 15 to 20, heated seats 20 amps each, then you have the drwa of the engine and its systems. which add up to a constant 20 amps all the time of power use. so 90 amps. but still not a lot of HP loss
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Originally Posted by Aarkie
Look at it this way. 746 watts equals one horsepower. The output voltage of the alt is about 14.5 volts. That means that you would have to have a current draw of 51.4 amps to be losing one horsepower. So if you put a big load on the power supply you will have to use more fuel to take care of it. But you can also look at it that if running unloaded that it takes 100 HP (I just picked a number) that a 50 amp load would take add 1% more power so it should be very little extra fuel.
