A modern economy car requires about 20kw (about 26 hp) to zip along at 70 mph.
If you prefer, you can dawdle along at 40 mph for only 10 kw.
Since
a gallon of regular unleaded contains about 114,000-125,000 BTU of
chemical energy and the typical conversion efficiency of an internal
combustion engine is about 20%, we get just about 7 kwh of mechanical
energy per gallon. (in other words about 25 miles per gallon)
Electricity is pretty cheap compared to gasoline burned in an
automobile engine. At ten cents per kwh delivered to my home it is only
a quarter of the 42 cents per kwh you get using $3.00 per gallon
gasoline. Industrial rates of 2.4 cents per kwh are one twentieth the
price of gasoline. (An emergency gasoline powered generator in my
backyard would cost about $1,000 per month to air condition my house.)
Then
consider a transit bus which gets about 4 miles per gallon and carries
an average of 10 passengers. This makes it equivalent to two passengers
in a 20 mpg car. Of course if you load that bus with 50 passengers vs 4
in the car you'd need a car capable of 50 mpg (like a hybrid) to get
the same fuel efficiency. Buses don't look like that good a deal,
especially since you have to pay the driver.
Cost factors in a
gallon of gasoline at $2.85 per gallon with crude at $60 per bbl - 50%
crude, 28% refining, 8% distribution & marketing, 14% taxes
With the improvements in battery technology spurred by computers and hybrid cars, plug in electric
cars are looking very attractive. With a conversion
efficiency of 90% an electric motor is quiet, capable of delivering
high torque and simple compared to all the effort it takes to build a
gasoline powered car. Subtract the AC and other parasitic losses it takes to run a car
and you are down to 75%. With 20 kw consumption at 70 mph and 10 cents
per kwh, you could whizz along at under 3 cents per mile vs 10 cents
per mile in a 30 mpg car.
Tesla
Motors is claiming 135 mpg equivalence and offering a home solar panel
that provides enough power for 50-80 miles per day of use in their $98,000 high performance two seater.
Aptera is building a car that will average 300 mpg (well in a way if you don't count the electricity).
And smart cars are on their way to America.
Of
course fuel is not the greatest expense in a car. The purchase price
including financing, registration and taxes, insurance, fuel and
maintenance add up to make the typical cost of driving at least 50
cents per mile and over $1 if you drive a new luxury vehicle.
* 3,400 BTU = 1 kilowatt hour
1 kw = 1.325 hp