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November 18, 2011

My Week Driving the Chevy Volt: Part 2


Last week, I reluctantly handed back the keys to the Chevy Volt that I had the opportunity to test-drive for seven days. As I wrote in my last blog post, it was a smooth, quiet, oil-free, and fun driving experience for my whole family.

This week, I challenged myself to make some calculations about what a switch to a Volt or another plug-in vehicle would mean in terms of my family's own emissions and oil use. I hope some of you will be inspired to make your own calculations if you haven't already.

According to a new very helpful Department of Energy Calculator, the emissions we spew into the air from the 2005 gas-powered vehicle that my husband and I share for carting around ourselves and our two daughters is a whopping 11,646 pounds each year (this makes me sick to consider). We purchase about 485 gallons of gas a year. Factoring in fuel, tires, maintenance, registration, license, insurance, (basically all but purchase price), the DOE tells me that our cost per mile is $.35.

If we drove the Volt, our emissions would decrease to 5,672 pounds per year (from a combination of tailpipe and smokestack sources in Massachusetts where we live), our gallons of gas purchased would go down to 159 gallons, and our cost per mile would decrease to $.25.

If we drove a fully electric Nissan Leaf, our emissions would drop to 4,169 pounds per year, our oil use would plummet to zero, and our cost-per-mile would be as low as $.18.  However, we frequently drive to visit family in other parts of New England, so we would need to borrow or rent a longer range vehicle -–thus throwing off my calculations (this would work better for a two-car family or one that makes infrequent trips over 100 miles).

If we drove a Prius, our emissions would be at 5,534 pounds a year, our fuel consumption would be 231 gallons annually, and our cost per mile would be $.27.

The plug-in Prius (for which Toyota coincidentally opened up the waiting list in certain states this week) is too new for the DOE calculator to let me determine my emissions. However, based on my own back-of-the-envelope calculations, if we drove the vehicle, we would purchase about 122 gallons of gas a year (the least among the cars not fully electric).

So, for me without taking into account the cost of the vehicles and the availability of charging infrastructure (subjects for other blog posts), the oil, emissions, and cost-per-mile benefits would improve as I go from conventional to extended range electric to plug-in hybrid to fully electric.

But, it's important to consider that some people live in areas where the grid is cleaner or dirtier than mine here in eastern Massachusetts (we have about 15 percent coal in our mix compared to well over 50 percent or as low as zero in some parts of the country). Also, one interesting thing I found in doing my own calculations was that the majority of my family's annual driving miles are on the highway for long-distance weekend trips, while the remainder are for short local trips under five miles. Most American drivers have different driving patterns. These factors will change your results.

I then considered what would happen if we installed solar panels on our roof, something we're planning to do in the next year or so. According to one National Renewable Energy Laboratory(NREL) study, relying on grid-connected solar for the electricity to power our home and vehicle would approximately halve our electricity-related emissions.  Mike Simpson, a Vehicle Systems Engineer at NREL's Center for Transportation Technologies and Systems, further explained to me that more important than anything we would be doing to reduce our own family's emissions, our solar could be offsetting the peak load demand on the grid, and the combined effect of a lot of people switching to solar may well reduce the need for new power plants.

What if we're not ready or able to switch to solar? Max Baumhefner recently suggested in an NRDC blog post that people should visit buycleanenergy.org where "for $20, you can buy enough RECs [renewable energy certificates] to cover a year's worth of driving."

Here is another interesting thing I learned about my own calculations: I grossly under-estimated the number of miles my husband I drive each year. When I added up what I thought we drove on a weekly basis (not too much given that we often walk, take the bus, or take the train) and then added our frequent trips to visit family in other parts of the northeast, I estimated a total of less than 6,000 miles a year. However, the odometer told me that the annual result was more than 11,000 annual miles (I checked my math many times and even took the car for a drive to check the odometer accuracy).

This made me wonder if other people are also under-estimating their miles driven, as well as their emissions, oil use, and spending on gasoline.  In fact, Consumer Reports says that it came up with a national average of 12,000 miles per driver per year from simply asking their survey respondents. If we're all underestimating the impact of our driving on our health, our environment, and our pocketbooks, then we’re in even worse trouble than we thought.

We already knew that a hybrid, plug-in hybrid, pure electric, or extended range electric vehicle is always going to be cleaner than a traditional vehicle, even on today's electricity sources (see our Sierra Club fact sheet). What many people may not realize is that determining our emissions and oil use is the result of a complicated equation that will greatly vary by person. It will depend not only on our choice of vehicle, but also on our electricity sources, the (real) number of miles we drive a year, how many long-distance  miles we drive (beyond the range of many of today’s EVs), and the percentage of those miles that are highway vs. city. Lucky for us, this new DOE calculator makes this easier to figure out.

As I work out what to do with my EV-withdrawl, I’ll end this post with words by Chuck Frank, a Sierra Club supporter and former owner of Z. Frank Chevrolet in Illinois who recently took delivery of his new Volt:

"I am proud to be an early adopter for a new technology in transportation.  I am delighted…that we don't have to have our foreign policy controlled by favoring oil rich countries….And I feel good about reducing the amount of CO2 I burn that is destroying our…climate.  I hope that as more electric vehicles come on the market at a price more people can afford, that more…people will join me in shaping the world that we will leave for generations to come."

-- Gina Coplon-Newfield, Sierra Club’s Senior Campaign Representative for Electric Vehicles


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