14

Some time in 2009, California passed new regulations, banning black cars (here's one source) on the grounds that black cars have higher emissions than other colors of cars. The theory is that black cars absorb more heat from the sun, so their A/C must work harder. Is there any truth to this?

And if there is, wouldn't it be beneficial in winter months to have black cars?

Oddthinking
  • 140,378
  • 46
  • 548
  • 638
Flimzy
  • 15,520
  • 14
  • 63
  • 132
  • 1
    That would assume (even just for summer) that everyone uses A/C all the times (which may be true in California, I don't know). – nico Oct 09 '11 at 08:25
  • They are certainly hotter without A/C in sunny places... – Sklivvz Oct 09 '11 at 08:46
  • @Sklivvz: To the touch? Or in the cabin? :) Source? (personal experience?) – Flimzy Oct 09 '11 at 17:50
  • @Flimzy: completely personal/anecdotal experience. I am referring to the inside of the car (so the air, but also the interiors). – Sklivvz Oct 09 '11 at 17:53
  • Like @Sklivvz says, I wonder if the important bit regarding heat and a/c usage is partially what colour the interior is, but also a general thought on glass: I think most of the internal temperature is down to solar radiation entering through the windows and hitting the upholstery and dashboard. A bit like a greenhouse, I guess. – Rory Alsop Oct 09 '11 at 18:23
  • I certainly agree that my black leather interior gets hotter than my brother's tan interior, when sitting in the same driveway, with otherwise identical car models. His car is white, mine grey, so my exterior color might be a "bit warmer", but I doubt it makes nearly as much difference as the black leather. – Flimzy Oct 09 '11 at 18:27
  • @GeorgeDuckett: I ask essentially that same question in my original question... – Flimzy Oct 09 '11 at 18:58
  • 1
    Btw, the proposed regulations never made it to law, primarily due to potential issues with reflective glazing interfering with mobile phone reception and so forth. [source](http://www.arb.ca.gov/lispub/rss/displaypost.php?pno=3918). Black cars (nor any other colour) were [not to be banned](http://www.snopes.com/politics/traffic/darkcars.asp) either. – Jivlain Oct 09 '11 at 22:21
  • I am not surly say that the black car consume more fuel than the others, but I have read some where that the black car absorbs more heat from sun lite and generates more combustion than the white or silver, due to this there is possibility of consumption of more fuel. – PeterMartin Feb 08 '12 at 09:26

1 Answers1

21

The "heater" in your car does not actually generate heat itself. It actually takes the heat generated by the engine and passes that back through your cabin rather than venting it outside. So neither heaters nor winter will increase CO2 emissions.

Californians use approximately 1.8 billion liters (472 million gallons) of fuel each year running car air conditioners (do note that this is of 76 billion liters, or 20 billion gallons total statewide - so air conditioners account for about 2.5% of fuel consumption).

The reason that lighter car colours could be used to reduce air conditioning use is that they reflect more incoming light rather than absorbing it and heating up. A black car can heat up by almost 6°C more than a white car.

So, yes, a lighter coloured car would reduce the need for air conditioning, lowering CO2 emissions.

Flimzy
  • 15,520
  • 14
  • 63
  • 132
Jivlain
  • 6,658
  • 1
  • 37
  • 47
  • Hat tip to @Sklivvz for the metrification. – Jivlain Oct 10 '11 at 00:25
  • So that leads to the follow up question. Does running the A/C really use up more fuel (at least in a significant quantity)? – JohnFx Oct 11 '11 at 04:37
  • @JohnFx: see the second paragraph of my answer - about 2.5% of fuel use goes to A/C for Californian drivers. – Jivlain Oct 11 '11 at 05:36
  • Should the answer be qualified to specify hot, sunny climates? I don't think car colour would make much difference in cloudy england. – matt_black Jan 15 '12 at 23:31
  • @matt_black: I would anticipate that it would make far less difference in London, yes. As the heater doesn't matter, however, it would only be a difference of magnitude. The question asked specifically about California, which is certainly one place in which the difference would be meaningful. – Jivlain Jan 16 '12 at 01:22
  • you forget something: reflectivity of visible light doesn't mean lower absorption of heat energy, which is mainly in the infra red part of the spectrum. – jwenting Feb 08 '12 at 11:50
  • It's worth noting that in the winter time a darker coloured car is a bigger *emitter* of heat than a light coloured one, thus it will need more heating. As Jivlain stated though, since heat is essentially a waste product from the engine it shouldn't cause an increased fuel consumption. – Highly Irregular Mar 28 '12 at 01:38
  • 1
    @jwenting, I think there's a strong association between darkness of visible colour and infrared "colour" in most cases though - the exceptions seem to be few and far between in my experience. – Highly Irregular Mar 28 '12 at 01:41
  • 1
    @jwenting What do you think happens to the visible light that gets absorbed by a black object? Its turns into heat... – Nick Aug 21 '12 at 16:39
  • In addition to cost to cool air there is also the additional cost of reduced fuel efficiency due to air current generation. For example cars are most efficient with the windows rolled up and least efficient when windows are rolled down due to aerodynamics. This in turn can be related to running the heat or ac as it causes a greater amount of air to be pushed through the car (as well as temperature controlled). It is worth noting rolled down windows are less efficient than pumping air through the car at speeds over say 20-30 mph. Ex why rolled down windows at 10-15mph is more efficient than AC – Tai Jul 14 '14 at 22:07
  • @jwenting As Nick said, we have conservation of mass/energy. Light energy cannot just disappear, it must change to another form of energy(eg. heat), or create mass. I don't think your black car gets heavier over time due to the sun :) – Cruncher Jul 15 '14 at 13:43