Wednesday, August 20, 2008

Electricity vs. Gasoline

I got fired up to write this article because of hippies. I think they are a frequent source of inspiration for us on this blog. In essence, I was reading a forum and as usual someone has to complain about people driving and that you should just move closer to work and bike. We'll that is great if you can do that, but it is obviously not a solution for everyone. (I am not going to get into the details here but... cost of living, city life, raising kids are good reasons.)

This example wasn't the entirety of my frustration. This kind of mindset is typical of the now more popular casual environmentalist claiming that individuals need to make drastic changes to their lifestyle (possible significantly detrimental ones) in the name of the environment. I think this kind of argument is bound to fail. Individuals will not change make significant changes easily, especially if they are going to inconvenience themselves. Instead, what should the environmentalist ask:

Can we create a global system which has the advantages of our current system without the pollution? How do we accomplish this? What technologies need to mature? What is the impact on the economy or the average joe's wallet? (it needs to be minimal, preferably create a system which makes money) How are we going to address growing energy demands?

If they maintained this attitude (an engineering approach to the problem - maybe they could actually get involved in the engineering and science themselves) they might make more significant changes. This is the point - the environmentalists agenda will not be fulfilled by making everyone feel guilty, instead it will happen if people can make money at it. This is only going to happen if technological advances allow it. Simple, science + money = solution, that is how you change the world.

Somewhere in the middle of this all I was researching carbon dioxide release from several energy sources. People have a tendency to blindly trust what they have been told. I asked myself, how much CO2 is created while driving a car vs. consuming electricity? Here are the numbers. A gallon of gasoline produces around 20 lbs of CO2. That may seem odd, since a gallon of gas only weighs about 6 lbs, but it is mostly carbon and it combines with oxygen from the atmosphere. O2 is much heavier than Carbon. Thus, heavier CO2.

On the other hand, a coal plant might produce around 2 lbs of CO2 per kWh. To put this in perspective lets say a home is using 11000 kWh/year. (An average value) This equates to around 22,000 lbs of Co2/year (if they ran off a coal plant) or maybe as low as 10,000 lbs of CO2. (if they have other combustion energy sources, natural gas, etc) This is equivalent to 500 to 1100 gallons of gasoline per year or 1.36 to 3.01 gallons per day. In a 30 mpg vehicle this equates to 40 to 90 miles of driving per day.

Thus, a 20-45 mile commute to work (everyday) in a vehicle with a reasonable gas mileage will produce about as much CO2 as a typical home.

I like numbers.


Eric Tarnowski said...

Your article got me thinking about the relative carbon dioxide output of electric vehicles vs. their gas powered counterparts. According to the Bureau of Transportation Statistics the average car in 2006 got 22.4 mpg while the average new 2006 car got 30.2 ( Combining that information with the rate of 19.4 lbs CO2/gallon of gas, we find that the average car in 2006 generates .8661 lbs CO2/mile while the average NEW car generates .6424.

According to a joint report by the Department of Energy and the EPA (, the average carbon dioxide output for electricity generated in the US in 1999 was 1.341 lbs CO2/kWh.

With that information at hand I began to look for efficiency information for electric cars. I was unable to find anything official for lead-acid batteries, the type of batteries used with previously available electric cars (i.e. EV1 which was available in CA from 1996 to 1999). The unconfirmed information I found said that the batteries for the EV1 could hold 18.7 kWh of energy and go for about 75 miles on a charge. That works out to .3344 lbs of CO2 per mile.

The next car I looked at was the Chevy Volt, a car that can run on either full electric, full gas, or in a hybrid mode. The Volt uses next generation Lithium-Ion based batteries and is being rushed to market by GM with a target launch date of sometime in 2010. According to, the Volt can go 40 miles on full electric using ~8 kWh of electric energy. That works out to approximately .2682 lbs of CO2 per mile for trips under 40 miles.

I found the numbers to be somewhat surprising. The new Volt, when it becomes available, will generate 58% less carbon dioxide than the average new gas-powered car does today. I expected that with our fossil-fuel dependent electric generation grid the reductions would not be as significant.

One thing for the environmentalists to keep in mind, however, is that a gas-powered car would only need to get 72 mpg to equal the carbon dioxide output of Volt in full electric mode. This is achievable with only incremental improvements in gas-electric hybrid technologies (the Prius is rated at 48 mpg today). Also, it is important to keep in mind that this rudimentary analysis fails to take into account the carbon dioxide output of the battery manufacturing and disposal process or the gas production and transportation processes.

For an entertaining look at anti-CO2 environmentalism taken out to its logical conclusion, see this article from Reason:

E.Jacob said...

Great Comments, I was hoping to run the numbers on electric vehicles, I just got sick of looking up the data. It is interesting how close an electric vehicle is to a gasoline or hybrid car. It is not the CO2 savior that it is advertised as. It is not a real solution to producing emissions. (unless we have all green electric power)

It is in the cost per mile that gives the electric vehicle its advantage. If gas is $4.00 a gallon, given a new gasoline car it costs $4/30 = 13.3 cents/mile, whereas the electric vehicle costs (given 10 cents/kwh, approximately the US average in 2006) 10cent/kWh*8kWh/40miles = 2cents/mile. Almost 85% cheaper.

I am interested to see the manufacturing energy consumption figures. I have not been able to find too much on the subject. Does creating an electric car use more energy than making a traditional vehicle? I'd like to know.

Eric Tarnowski said...

The savings associated with electric vehicles are deceiving too, however. The 2 cents per mile cost is just the cost of the fuel. It fails to take into account the increased upfront cost of an electric car.

The best numbers I can find suggest that the average incremental cost of an electric car is $1000 for every 10 miles of range. If we use the 40 mile full electric range of the Volt and consider that to be close to equal with the average distance driven by most people (works out to 14600 miles/year), then the incremental cost of the electric car works out to about $85 to $130 additional per month depending on your loan terms. That represents an incremental cost of 7 to 11 cents per mile. This means that the true relative cost per mile is ~9-13 cents for electric and 11-13 cents for gas (depending on gas prices). Pretty much the same.

Of course as battery production increased, those incremental costs would go down. That's why the best case would be a fully nuclear electric generation infrastructure and all-electric cars...

E.Jacob said...

Ah yes, you are right. That cost premium also applies to hybrids as well. I suppose all these solutions really don't make as significant of a change as people present.

I agree fully with the nuclear + electric solution. The use of electric vehicles has advantages in our combustion energy plants as well. In the evening electric power plants reduce their net output due to reduced demand. This causes efficiencies to fall. Having large numbers of electric vehicles could cause an evening out of electrical consumption and thereby driving up the net efficiency of power plants.

I personally would like to see an increase in mass transit and a reduction or elimination of vehicles in cities (or maybe limited to small electric vehicles) to reduce emissions and cost. I do not think that our current system can scale much larger, and after seeing the ineffectiveness of switching to electric vehicles, it seems as if we need a change in how we think about transportation.