Of course, electric really isn't doing much good environmentally since it just means we'll be burning more coal, but as the nuclear plants become more prevalent and coal is phased out some, it could really help some.
FROM THE WEBSITE:
(For a more detailed version of this argument, please see the white paper written by Martin and Marc.)
A common rebuttal to electric vehicles as a solution to carbon emissions is that they simply transfer the CO2 emissions to the power plant. The obvious counter is that one can develop grid electric power from a variety of means, many of which, like hydro, wind, geothermal, nuclear, solar, etc. involve no CO2 emissions. However, let’s assume for the moment that the electricity is generated from a hydrocarbon source like natural gas, the most popular fuel for new US power plants in recent years.
The H-System Combined Cycle Generator from General Electric is 60% efficient in turning natural gas into electricity. “Combined Cycle” is where the natural gas is burned to generate electricity and then the waste heat is used to create steam that powers a second generator. Natural gas recovery is 97.5% efficient, processing is also 97.5% efficient and then transmission efficiency over the electric grid is 92% on average. This gives us a well-to-electric-outlet efficiency of 97.5% x 97.5% x 60% x 92% = 52.5%.
Despite a body shape, tires and gearing aimed at high performance rather than peak efficiency, the Tesla Roadster requires 0.4 MJ per kilometer or, stated another way, will travel 2.53 km per mega-joule of electricity. The full cycle charge and discharge efficiency of the Tesla Roadster is 86%, which means that for every 100 MJ of electricity used to charge the battery, about 86 MJ reaches the motor.
Bringing the math together, we get the final figure of merit of 2.53 km/MJ x 86% x 52.5% = 1.14 km/MJ. Let’s compare that to the Prius and a few other options normally considered energy efficient.
The fully considered well-to-wheel efficiency of a gasoline powered car is equal to the energy content of gasoline (34.3 MJ/liter) minus the refinement & transportation losses (18.3%), multiplied by the miles per gallon or km per liter. The Prius at an EPA rated 55 mpg therefore has an energy efficiency of 0.56 km/MJ. This is actually an excellent number compared with a “normal” car like the Toyota Camry at 0.28 km/MJ.
Note the term hybrid as applied to cars currently on the road is a misnomer. They are really just gasoline powered cars with a little battery assistance and, unless you are one of the handful who have an aftermarket hack, the little battery has to be charged from the gasoline engine. Therefore, they can be considered simply as slightly more efficient gasoline powered cars. If the EPA certified mileage is 55 mpg, then it is indistinguishable from a non-hybrid that achieves 55 mpg. As a friend of mine says, a world 100% full of Prius drivers is still 100% addicted to oil.
The CO2 content of any given source fuel is well understood. Natural gas is 14.4 grams of carbon per mega-joule and oil is 19.9 grams of carbon per mega-joule. Applying those carbon content levels to the vehicle efficiencies, including as a reference the Honda combusted natural gas and Honda fuel cell natural gas vehicles, the hands down winner is pure electric:
Car Energy Source CO2 Content Efficiency CO2 Emissions
Honda CNG Natural Gas 14.4 g/MJ 0.32 km/MJ 45.0 g/km
Honda FCX Nat Gas-Fuel Cell 14.4 g/MJ 0.35 km/MJ 41.1 g/km
Toyota Prius Oil 19.9 g/MJ 0.56 km/MJ 35.8 g/km
Tesla Roadster Nat Gas-Electric 14.4 g/MJ 1.14 km/MJ 12.6 g/km
The Tesla Roadster still wins by a hefty margin if you assume the average CO2 per joule of US power production. The higher CO2 content of coal compared to natural gas is offset by the negligible CO2 content of hydro, nuclear, geothermal, wind, solar, etc. The exact power production mixture varies from one part of the country to another and is changing over time, so natural gas is used here as a fixed yardstick.
