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Old 10-28-2011, 03:40 PM   #1 (permalink)
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Default Excellent EV Ownership Cost Calculator Available

Doug Tiffany, a University of Minnesota Extension educator and economist has developed a spreadsheet to help compare the total cost of ownership, the greenhouse gas emissions of conventional, hybrid, electric, and extended range electric vehicles.

There are a number of these calculators around. This is by far the best of the lot. It factors in all of the complexities while maintaining a format that is easy to follow. Tiffany has filled in the sheet with some example numbers, however all of the numbers in yellow can be updated by the end user, which is good because although I am grateful for the work he has done here, I have some issues with his example numbers.


My own experience over 14,500 miles is that 91% of my miles have been electric. That includes a long drive home from the dealer, because the car was not available in my area when I bought it. Now that the Volt has rolled out nationwide that will not be the case for most.

Also, data from the Volt Stats web page shows a “fleet” average of 73% for 175 Volts that are submitting data. Many of these cars are early buyers like me who traveled great distances to buy their cars. The fleet average has been steadily going up.

The cars are even broken down by geographic area so you could see how cars in your area are doing to get a sense of range for your area. It is possible to get a sense what percentage of your miles will be electric before you plunk down your money. For example, if your commute is 40 miles or less round trip, you can pretty much figure on being north of 90% electrical usage. If you can work out a charging situation at work you can do 80 electric miles in a day easy. I routinely do over 100 all electric miles in a day no problem.

Think of it this way. How many hours in a day do you spend driving? 1 maybe 2 tops? That means for 22-23 hours out of everyday your car is just sitting somewhere, which is time that it could potentially be charging.

Looking at the way the spreadsheet is setup the percentage of miles driven electrically versus on gas is naturally a very big driver on overall costs, both for fuel costs but also for engine maintenance costs. Thus using his 53% figure he derives a monthly fuel cost of $72.92. That number would just about cover all of my fuel costs for 14,500 miles I have driven.


That just is not going to happen. Yes the warranty runs out in 8 years, that doesn’t mean it dies the day after the warranty ends. Nissan and GM are saying 80% of range after 8 years and 70% of original range after 10. GM appears to be putting its money where its mouth is and guaranteeing at least 70 or original range up to 8 years. No such guarantee from Nissan. But even if the range is reduced after 8 years to a point where you need to do something, you would likely only have to replace some cells. Or in my view more likely, battery costs are falling and battery tech is evolving very quickly. Dollars to doughnuts in 8 years we will have something much better and much cheaper.


Based on the GHG levels it appears Tiffany is assuming that 100% the electricity used in your car will be produced by coal. This maybe the case for some people, but for most people that number will be far lower. In 2009, the last year for which data is available, that percentage of coal generated power was 45%. This is down from 53% in 2007. Natural Gas and Renewables showed gains over that time. And if the number applications for Nuclear plants is any indicator we can expect the portion of Nuclear generated power to increase. Nuclear’s GHG are almost negligible at 60lbs/MW compared to coals ~1800lbs/MW.

You can easily determine what portion of your energy usage is coal or otherwise. Many power companies offer the alternative to buy low GHG electricity, though usually with a higher tariff.

In my own state of VA the split is about half coal and half nuclear. Although the portion at night tips in favor of Nuclear, which is the time when many people would be recharging their cars.

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Old 10-31-2011, 11:55 PM   #2 (permalink)
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Default Re: Excellent EV Ownership Cost Calculator Available

Further review of Mr. Tiffany's excellent EV/EREV cost calculator finds that Mr. Tiffany has provided data from the DOE showing the "regional" GHG emission rates. Note these figures are from 2007, and it is my understanding that the use of coal has decreased approximately 8% since that year.

I had taken exception to the 1784 lbs/mw number for my home state of VA. I computed a number of ~801 lbs/mw based on the understanding that Virginia generates about half of its power from coal and half from nuclear. However, as the DOE data reminded me, at certain times of the year VA does not produce all of its own power, and must therefore import power. What Mr. Tiffany has done is to provide us the GHG emissions for those regions which share power.

The emission rate for the region in which VA falls is 1125. However, if we wanted to be absolutely accurate we would have to come up with some sort seasonally weighted average, and we would also need to factor in the time of day that charging would occur because different sources are more prevalent for generation depending on the time of day.

It is a complicated business. But this spreadsheet makes it easy for you to adjust according to which number you think are most accurate for the particulars of your situation.

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Old 11-01-2011, 03:40 AM   #3 (permalink)
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Default Re: Excellent EV Ownership Cost Calculator Available

Another thing the spreadsheet doesn't take into account is leasing. There is a lease/buy decision for each vehicle as well.

For an EV a lease may be more economical because you have a lower monthly payment, and you don't have to worry about that 8 year battery replacement issue as you've gone through at least two vehicles by then. Granted the lease option may not be as green as owning the thing and driving it into the ground but it is another option that may reduce the ownership cost.

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