Even very slightly? I know that using the air conditioning certainly does. What about headlights?
Theoretically it does increase the load on the alternator, but I doubt you could measure any change in fuel consumption. The radio will typically use a few tens of watts, while a car engine puts out many kilowatts.
FWIW,
Rob
My chemistry teacher did this one on the board years ago. Answer, yes, but not so’s you’d notice. I think it came out to going a few less feet per tankful.
Yes. You can’t get something for nothing. The power for the radio is supplied by the battery which is supplied by the alternator. The alternator takes power from the engine.
Would you notice if you didn’t run your radio for a tank? No.
But in a perfectly controlled experiment where you drive an entire tank at an exact set speed in a climate controlled atmosphere - maybe you notice the difference.
If you have 4 20" subs with a couple of thousand watt amps it’ll be a little more obvious.
ETA- oh sure! no answer for 10 min then an almost quad simulpost.
It would be tolerably strange to hear that the energy to run automotive electrical accessories came from anywhere other than the fuel that’s burned by the engine.
Well, the follow-up question is: How many watt-hours in a gallon of gas, assuming average efficiency of tranmission of electrical energy from the engine to the alternator?
[cranky] The real question is how much carbon we can save if we legaly mandate that peopel can not listen to the radio! [/cranky]
I remember reading somewhere that headlights increase fuel usage by about 1%, but I can’t find it now.
-Eben
Mine has a crystal set.
Not really.
It would also depend on the amp draw of your stereo. If you have a stock stereo, the draw is practically nil.
However, if you have a multiple amp-driven system like I used to in college, then it’s different. My alternator was rated at 70 amps and my system consumed 40 of that…you know, just for the stereo.
I even had a capacitor to provide extra energy for bass peaks but still my headlights dimmed on bass hits and my rpms would fluctuate. Needless to say I went through some alternator belts.
Ahh, misspent youth…and hearing.
Headlights on many cars draw enough power that you can hear the engine slow down if you’re sitting and idling and turn the lights on and off.
>It would be tolerably strange to hear that the energy to run automotive electrical accessories came from anywhere other than the fuel that’s burned by the engine.
Not all that strange - there’s a fair number of automotive electrical accessories that run on replaceable batteries, perhaps to avoid having to run power wires. Dashboard GPS units, radar detectors, electronic compasses, and stick-on clocks come to mind.
Right. I was thinking more of the accessories that tend to be included with the car.
I work with a very frugal woman. Very frugal.
She gave me a lift one night (yes, I paid for gas), and leaving the staff carpark, I reminded her that her headlights were off.
“Oh yes, I know. It saves fuel! I’ll turn them on when we get to the street.”
I told her it didn’t affect fuel consumption at all. I think I knew it did slightly, but I didn’t want her careening about the carpark with her lights off.
Take the LHV of gasoline (Home - Transportation Energy Data Book Transportation Energy Data Book , pg B-4) at 115,400 Btu/gallon, then at 3,413 Btu/kWh we get 33.8 kWh/gallon. Now we assume that the car engine turns the energy in the gasoline into rotating energy at about 20% efficiency (various), and then assume that an alternator is about 55% efficient (Alternator - Wikipedia).
This means:
33.8 kWh/gallon * 0.2 * 0.55 = 3.72 kWh electricity per gallon
I look at it like this:
One horsepower is equivalent to 746 Watts of power. Let’s say your car’s engine produces 150 horsepower. Let’s say the stereo consumes 100 Watts.
The math tells me that your stereo consumes less that 1/10th of 1% of the total available power output of the engine.
Remember that you don’t typically drive around at wide-open-throttle, you tend to drive around at the power needed to overcome rolling resistance and wind resistance. In some cars that can be as little as 5-20hp for a low-speed cruise. The radio power is still a small number, but a larger percentage.
I did some of the math and looked up the numbers in another thread, to determine how much range would be lost in an electric car with all the accessories on. Headlights consume between 35 watts (HID) and 55 watts of power, typically.
A gallon of gas burned through a 100% efficient generator could run your headlights for about 60-100 hours.
True! :smack:
I thinking powering the radio uses way less energy than hauling around the huge ass loaded purse that some women do. Then again how much energy will losing 20 pounds in fat save you. I bet it more than pays for the radio energy. Somebody should figure out how much fuel you save by reducing weight and use that as an announcement on the news every night, instead of telling us again that gas prices changed. After the last three years we know the price is different every trip, do something to educate, not reiterate.
Here’s a quicker idea - take the junk out of the trunk. A lot of people drive around with a lot of useless crap in the trunk of their cars. That hurts acceleration and mileage.