An article in Business Week Online tells us that experimental hybrid cars get up to 250 mpg (a very similar article appeared in the New York Times business section a couple of months earlier). I enjoy reading between the lines of lay press science and technology articles. There was a great discussion in Grist on this subject not too long ago.

Gremban …spent… $3,000 tinkering with his car… [I]n the trunk sits an 80-miles-per-gallon secret — a stack of 18 brick-sized batteries… [T]he extra batteries let Gremban drive for 20 miles with a 50-50 mix of gas and electricity.

In other words, for his $3000 he will get 80 miles per gallon for 20 miles before his carriage turns back into a pumpkin. For the rest of the day he will carry a hundred pounds of bricks around in his now-useless trunk, which by the way will degrade his gas mileage. For the first 20 miles he drives each day he will save 0.25 gallons, thus recouping his $3000 in about twenty years, assuming his batteries last that long. The more miles he drives after the batteries go dead, the worse things get because of the extra weight of the dead batteries in his trunk. Which leads me to ask: If his commute is only ten miles each way, why not just ride a bike, get a little exercise, and save $3000? You can also get 80 mpg out of a 40-mpg car by carpooling with one passenger, or get 120 mpg with two passengers, or 160-mpg with three passengers.

Monrovia-based Energy CS has converted two Priuses to get up to 230 mpg by using powerful lithium ion batteries. It is forming a new company, EDrive Systems, that will convert hybrids to plug-ins for about $12,000

In other words, you will get up to 230 mpg (the equivalent amount of oil burned by the power plant to charge you up) before the batteries that are powering the car go dead. Oddly enough, they forgot to mention how many miles you could go before that happened. You will then turn back into a hybrid and lug $12,000 worth of discharged lithium-ion batteries around with you all day until you can get to an outlet for five or six hours.

University of California, Davis engineering professor Andy Frank built a plug-in hybrid from the ground up in 1972 and has since built seven others, one of which gets up to 250 mpg. They were converted from non-hybrids, including a Ford Taurus and Chevrolet Suburban. Frank has spent $150,000 to $250,000 in research costs on each car, but believes automakers could mass-produce them by adding just $6,000 to each vehicle’s price tag.

In other words, after having spent millions of somebody’s dollars dinking around, he believes it would only cost an extra $6000 to mass-produce plug-in hybrids that presumably have similar performance to the ones mentioned above. So take your pick. Will it cost an extra $3000, $6000, or $12,000 to save between 65 cents to a dollar a day on gas, depending?

20 miles/40mpg=0.5 gallons, 0.5 gallons x $2.5 = $1.25.
20 miles/80mpg=0.25 gallons, 0.25 gallons x $2.5 = $0.625
$1.25-$0.625=$0.625

20 miles/240mpg=0.083 gallons, 0.083 gallons x $2.5 = $0.21
$1.25-$0.21=$1.04

After all of this you might assume I am against plug-in cars. Actually, I’m not. I think they have great potential. You just can’t have your cake and eat it too. They will cost more. The Prius is popular for five main reasons: It has reasonable performance, gets great gas mileage, is aesthetically appealing, of excellent quality, and reasonably priced.

Screw up any of those parameters (add six thousand dollars to its price) and watch what happens to its popularity. If enough people want plug-ins bad enough (are willing to pay for them) they will get them.