Is a gas car better than a coal car?


There has been a bit of discussion that a plug in hybrid car is really a coal car.  I believe that this true statement is meant to actually scare consumers from buying or hoping to buy an all-electric vehicle or a plug-in hybrid.

Let’s do a bit of napkin math and assume that energy transmission losses (and other losses) are negligible or at least cancel each other out.

Some quick math:

  • Gasoline – .0001686 pounds of CO2 per BTU generated
  • Coal – .0002 pounds of CO2 per BTU generated

This is a virtual tie!  Not really of course, a mathmetician will point out that there is a 16% difference.  But the mechanical engineer in me calls this a tie.  This is because I understand that there are some inherent inefficiencies in both conversion processes.  A great deal of the energy of gasoline is used to make the engine warmer and a great deal of the electricity is lost to transmission as well as the inefficiencies of charging batteries.

Of course, the part of this discussion that is lost is the infrastructure that is required to create that much electricity.  The Oil Drum has a discussion on this subject that may scare you if you think that we can add a million or two plug-in electric vehicles with our present capacity.  Although Autobloggreen suggests that there is no problem as long as the vehicles are plugged in “off-peak” which typically means in the late evening or overnight.

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3 thoughts on “Is a gas car better than a coal car?”

  1. tim maguire says:

    How do the scrubbers and other smoke stack cleaning technology in the power plants fit into the calculations? Or are they already in there?

  2. admin says:

    Tim –

    The scrubbers and other cleaners are really for soot, sulfur and other pollutants. As much as we like to talk about the ability to capture CO2 leaving the smoke stack of our coal plants, that technology is really not in place for the vast majority of our electrical generation. Therefore, the scrubbers really affect the conversation in that they use energy that can’t then be delivered to the consumer. This is just one in many factors that bleed off the efficiency of the system.

    Unfortunately both systems are fairly efficient. A great deal of the energy of petroleum is wasted rather than move the car down the road. Likewise, a great deal of energy is wasted from the time it is created in the plant to the time it reaches your light switch.

    At some future time, I would like to write a piece about the various levels of efficiency in the two systems.

  3. tim maguire says:

    Thanks for the reply. So smoke stacks offer one “bottleneck” that could be used in carbon capture (even if not widely used now), but at the cost of efficiency?

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