EV MPG is just a way to compare range and cost between electric cars and gasoline powered cars. Electric vehicles do not use gallons of anything, so you are just making a comparison to the familiar standard of miles per gallon when you convert electric energy
use to mpg.
Electric car energy economy can measured by how many Kilowatt Hours (kWh)
used per mile, since kWh is the measure of energy used.
Take the new Nissan Leaf as an example. The Leaf battery pack holds 24 kWh full up.
24 kWh is the same energy as a medium sized window air conditioner (1 kWh) running
for 24 hours.
Battery packs actually do not like to be discharged below 80% of their full rating, so you
have 0.8 x 24 = 19.2 kWh of useful energy in that Leaf. This is what you will be charging
up at your house or wherever.
The costs below assume 100% efficiency, which never happens. They are close enough
for an illustration of EV MPG though. All costs are in USD.
Here in this office, electricity goes for $0.122 per kWh. So, it would cost us:
19.2 x $0.122 = $2.34 to charge up that Leaf. NOTE: your electricity cost may be higher!
The advertised range of the Leaf is 100 miles. Here are the average mileage numbers:
For cost per mile, $2.34/100 = 2.34 cents per mile
This cost is very low compared to the gasoline powered car per mile. However, the electric car battery pack costs a lot to begin with...in the neighborhood of from $5,000 - $15,000. This is where the electric car runs into practical problems. Government subsidies do help lower the cost, but most people will not want to pay more upfront.
EV MPG from E-Bikes
One of our DIY projects has been e-bikes from kits. These machines end up getting over 2,000 mpg! Here's how:
Our DIY e-bikes hold about 1/2 kWh worth of energy.
One gallon of gas has about 36 kWh.
There are 128 ounces of fluid gas in a gallon.
So, 128 ounces gasoline per gallon / 36 kWh = 3.6 ounces gasoline per kWh energy
And, 3.6 oz x 1/2 = 1.8 oz gas equivalent per 1/2 kwh = 1.8 oz gas equiv per charge up
The e-bikes will go around 30 miles per charge.
So, 128 ounces per gal gas energy / 1.8 ounces gas equiv per charge = 71 charges per gallon.
71 charges per gallon x 30 miles per charge = 2,133 miles per gallon
We can do this every day for 1,200-1,500 charge cycles; about three years!
If you want motorized transport, ride an e-bike or drive an EV.
