|Photo credit: Lincolnloop.com|
I was reminded of that post by this article in Energy Trends Insider. The article discusses a construct from the Department of Energy (DOE) at a new website that discusses the so-called "eGallon." This number purports to give the quantity (or cost) of the electricity that it would take to move a "typical" electric vehicle (EV) as far as a gallon of gasoline takes an "average" conventional car. This is where the "low hanging fruit" concept comes in. Replacing a 20 m.p.g. vehicle with an EV saves MUCH more than replacing a 30 m.p.g. vehicle. The 30 m.p.g. vehicle goes half again as far on a gallon and thus the eGallon costs more for that driver.
I applaud the DOE for attempting to clarify the possible savings in fuel expenditure vs. electricity expenditure but, in some cases, it may be very misleading. The calculation is further complicated by the wide variance in how electricity is priced in various localities.
As to the "low hanging fruit," the plot below shows, for a driver who drives 12,000 miles per year, how many gallons of fuel are saved per year by moving from one m.p.g. driving regime to a higher one. It plots initial m.p.g. from 10 to 40 and final m.p.g. from whatever was the initial m.p.g. to 120 m.p.g. The "front" axis is initial m.p.g., the axis that extends back and right is final m.p.g., and the vertical axis is gallons saved. As can be seen in the rightmost portion, the savings from a high starting point are not nearly as large. It's also easy to see, especially at the left end, that the big gains are in the initial improvements - the slope is dramatically steeper than at the higher final numbers.