PLUG OK license plate
Energy expert Joe Romm on CO2 emissions of gas and electric cars
Jun 13, 2005 (From the CalCars-News archive)
This posting originally appeared at CalCars-News, our newsletter of breaking CalCars and plug-in hybrid news. View the original posting here.
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I'm passing on this explanation from Joe Romm -- if you want to see more about his book, see­.
See more on this subject at Section 3 of CalCars' Vehicles page­vehicles.html

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Hi, I'm Joe Romm.

I ran the Office of Energy Efficiency and Renewable Energy at the US Department of Energy during part of the Clinton Administration and wrote "The Hype about Hydrogen" (Island Press, 2004).

Plug ins are so new for most of us that we haven't done a very good job of putting out basic fact sheets. Heck, I didn't even talk about them in my book. I just got educated by a bunch of people, including Felix. Then I wrote a paper for the National Commission on Energy Policy which helped spur a great deal of interest.

Hybrids that can be plugged into the electric grid (so-called plug-ins or e-hybrids) will be I think the second phase of a two-phase transition that has already begun with the hybrid revolution. The top priority for all of us who want to reduce oil consumption and greenhouse gas emissions in the transportation sector is certainly increasing fuel economy standards. I personally would recommend these standards give some sort of extra credit for meeting the standards with hybrids because we want to enable the second phase of the transition, where dual-fuel hybrids can run partly off of a charge from the electric grid.

Electricity has always been the ideal fuel for driving, because electric motors are so efficient (but range and speed of refueling issues limited the attractiveness of pure EVs). This is especially true in cities because electricity-powered cars have zero in-airshed emissions and 10x to 1000x lower lifecycle emissions of all criteria air pollutants, and potentially zero life-cycle emissions in the long term as the grid gets cleaner.

My top priority has always been greenhouse gas emissions. Here plug ins are an unadulterated home run. Let's use the high-end of actual numbers that Felix Kramer has been getting with his modified Priuses: 250 Watt-hours per mile all electric (this should be pretty typical for modern EVs of that size -- The large RAV4 gets maybe 300 Wh/mi). Let's compare that to what a diligent driver will get with the Prius in warm climates: 50 mpg (personally, my family does on average about 46 mpg year round).

Let's compare 12,000 miles (the typical yearly vehicle miles traveled), running all electric, which consumes 3,000 kwh, with running all gasoline (i.e. using a regular Prius), which would be 240 gallons.

The lifecycle greenhouse gas emissions from burning a gallon of gasoline is roughly 25 pounds (20 on-site, another 5 in the petroleum production chain -- the number may be slightly higher for reformulated gasoline, and will be considerably higher from oil from the tar sands). So we have 6,000 pounds of CO2 from a Prius.

NOTE: The average new NON-hybridized car would emit 11,000 to 12,000 pounds of CO2. This is the proper baseline for those who are concerned about whether e-hybrids would increase emissions compared to a business as usual case.

The grid average emissions factor for electricity in this country is, roughly, 1.3 pounds per kwh. That yields 3,900 pounds of CO2! So running your E-hybrid on the U.S. grid is 35% better than running a Prius on gasoline and 65% better than an average car.

If the entire grid were coal, you could double that (7,800 pounds), so even in that worst-case scenario, you'd still have far LOWER CO2 emissions from a plug-in Prius than from the average new car on the road running on gasoline.

In California, with its cleaner grid, you'd have under 2,000 pounds emissions from a plug-in Prius. And, of course, people can choose to purchase 100% renewable power.

The nice thing about plug ins is that it gives people a fuel choice, and everyone will choose electricity since even in California, the per-mile cost of electricity is under one half that of gasoline.

Joe Romm

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