plugging-in-to-coal2Quick-draw critics of the electric car often criticize EVs because, in their words, “Electric cars simply replace a tailpipe with a smokestack.”


The gist of their argument is that emissions still occur, not at the tailpipe but at the electric power plant. That observation is usually followed by the statement that 45% of our grid electricity is powered by coal and coal is dirty. Thus, the EV supposedly provides no net gain.

The critics may want to look in the mirror — or in their garage.

In California, oil refineries are the second largest users of electricity. Moving water around the state via water authorities is the single largest contributor to state electricity use. And, you guessed it, refining crude also takes a tremendous amount of water!

Doing the electric math on the oil refining process

refineryThe United States uses more petroleum than any other energy source. Petroleum provides the U.S. with about 37% of the energy we use each year.

Petroleum can’t be used as it comes out of the ground. It must be refined before it can be used.
Oil refineries use a lot of energy to convert crude oil into gasoline, diesel fuel, heating oil, chemicals, and other products. Almost half of a refinery’s operating costs (43%) are for energy (U.S. Energy Information Administration).

In a 2008 report, Argonne National Lab estimated that the efficiency for producing gasoline at an average U.S. petroleum refinery is between 84% and 88% (Wang, 2008), and Oak Ridge National Lab reports that the net energy content of oil is approximately 132,000 Btu per gallon (Davis, 2009). It is commonly known that a barrel of crude oil generates approximately 45 gallons of refined product (refer to NAS, 2009, Table 3-4). Thus, using an 85% refinery efficiency and the aforementioned conversion factors, it can be estimated that about 21,000 Btu—the equivalent of 6 kWh—of energy are used per gallon of gasoline refined.

6 kWh to refine gallon of gas
It is a simple fact that the refining of gasoline requires approximately 6 kWh of electricity per gallon of gasoline.

In fact, electricity and natural gas cost are estimated to comprise 43% of the U.S. oil refineries’ total expenses. If you tack on the energy required to extract and transport the oil to the refinery and then to the gas stations as well as the energy cost of the gas station, I’m sure that number jumps a few more kWh per gallon.

So, let’s be conservative and cut the oil guys a break and say it takes 8 kWh to extract, ship, refine and transport each gallon of gas.

What’s good for the goose is good for the gander. Drum roll: It takes more electricity to drive the average gasoline car 100 miles than it does to drive an electric car 100 miles.

Gas cars & electricity use
A gas car that runs at the U.S. fleet average of 21 mpg will consume approximately five gallons of gasoline to travel 100 miles. Using our 8 kWh of electricity per gallon figure, this means that gasoline car uses approximately 40 kWh of electricity to drive 100 miles. An electric car will use approximately 30 kWh of electricity (3.3 miles per kWh) to drive the same 100 miles.

In sum, gas cars use more electricity than EVs, thus polluting at the smokestack. And they burn refined gasoline in a very inefficient engine, thus polluting at the tailpipe. In our large urban cities in the U.S., the emissions caused by our transportation fleet account for 70% or more of our man-made emissions and visible particulate matter (smog) and related health care costs. Think of that as smoking two packs of cigarettes.

Electric cars run on electricity created by a mixture of energy sources. Many electric car drivers such as myself quickly discover that making your own electricity via solar PV is the best and cheapest way to fuel (about $0.40 per gallon of gas equivalent). Think of that as cleaning up the air in our major cities, saving money and as not smoking.

Peder Norby is a long-time solar-charged driver from Carlsbad, Calif. SolarChargedDriving.Com would like to thank him for allowing us to re-publish this column, which originally ran on Peder’s Electric Mini Blog.

U.S. Energy Information Administration:

Davis, S., Susan W. Diegel, and Robert G. Boundy. (2009). Transportation Energy Data Book, Edition 28. National Transportation Research Center, Oak Ridge National Laboratory.

NAS. (2009). Hidden Costs of Energy: Un-priced Consequences of Energy Production and Use. The National Academies Press.

Wang, M. (2008). “Estimation of Energy Efficiencies of U.S. Petroleum Refineries,” Center for Transportation Research, Argonne National Laboratory.

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