How many gallons in a volt?

GM recently announced the Chevy Volt, due out in 2010, will get an amazing 230 miles per gallon in city driving.  This number is an estimate based on an estimate of the final EPA rating process for this type of electric vehicle.  The Volt is designed to run about 40 miles on a full charge, and then run a small gasoline motor to provide electricity to drive the car once the battery has run down.

Suppose you use the Volt to commute, and your job is 10 miles from your home.  Since you never drive over 40 miles a day, you never use the gas engine, and your real MPG is infinite. I’d take that.  On the other hand, the Volt will supposedly get around 50 MPG when running with the gas engine.  So if you go on a 240 mile trip, your mileage is really about 60 MPG.  Not bad, but not 230 MPG either.

Cars that run solely on electricity also get a MPG rating.  For example, the Tesla Roadster is rated at 135 MPG.  The BMW Mini E is rated at about 100 MPG using a formula that sets one gallon of gas equal to 33.7 kW-hr.  How that formula was created isn’t specified.

Only an idiot would attempt to rate an electric vehicle or a hybrid according to the amount of gasoline it uses.  The complexity is evident.  Unfortunately, since there are laws that affect car manufacturers based on the EPA MPG ratings of the fleets they have for sale (the Corporate Average Fuel Economy or CAFE), we all have to try to make sense of this idiocy.  If fleets do not meet the defined standard, the car manufacturer has to pay a penalty.  This encourages increases in fuel economy by increasing the cost of inefficient vehicles.

In order for this system to continue to work, the EPA needs to create a new rating system that rates the fuel efficiency of electrics and hybrids on the same scale as your 1967 VW Beetle.  Any adjustments to the CAFE rules are politically sensitive, as the car and oil companies have an enormous amount of clout.  These new rules will require making a lot of assumptions in order to compare unlike things, and science is often not the primary consideration.  So the process of making changes is incredibly slow and convoluted.

The simplest way to reduce the use of gasoline is to increase the gas tax and let market forces encourage people to conserve fuel.  Let consumers choose to buy efficient cars or cut costs other ways, by driving less or taking mass transit.  But taxes are politically difficult, so CAFE was created to try and accomplish the same thing without costing politicians too many votes.  Actually, CAFE mutes the conservation effect by hiding the cost increase from the consumer. Also, CAFE doesn’t take actual fuel use into consideration. If I buy a Hummer, CAFE penalizes that purchase. But if I don’t drive very often, I use less fuel than an “environmentally conscious” Civic owner who commutes 50 miles each way every day.

Whether there’s a tax or a CAFE penalty, in the long run the consumer pays the cost.  Now, especially since cars that use alternative sources of energy are becoming available, CAFE is a relic that should be discarded.

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