You'd also have to consider the efficiency of the gas generator in that scenario. If you're talking about a small gasoline generator, of the type people take on camping trips or to power a house in an emergency, I would presume that they're basically like lawnmower or motorcycle engines, which aren't very efficient -- likely less efficient than a car's engine, although I haven't looked into this issue and so am far from certain about it. I haven't seen this question addressed directly in any of the reporting I've seen on the issue, but reading between the lines, the impression I get is that EVs produce less CO2 pollution than gas-powered cars, even in areas that rely heavily on coal or oil for electricity, for two main reasons:
- Regenerative braking
- Big coal- or oil-fired power plants are more efficient than the small internal combustion engines in cars
The second factor isn't huge (IIRC, it's about a 10% or 15% efficiency gap), and so it's overwhelmed by transmission losses, losses in charging and discharging batteries, and the inefficiency of electric motors (which are about 90% efficient, which is good, but there are still losses there). When you compare an EV to a gas-powered hybrid car, the hybrid ends up producing less CO2 in coal-heavy areas. (Check the chart for West Virginia on
the DOE site I referenced earlier -- EVs beat conventional gas-powered cars, but not hybrids.)
EVs beat hybrids in states heavy on natural gas (such as Rhode Island) because natural gas power plants are more efficient than coal or oil power plants, particularly on a CO2 emissions basis. Start adding in a significant amount of renewables and it just gets better.
Of course, you've got to balance the reduction in CO2 production per mile driven with the increased CO2 production when manufacturing the EV, too. To a lesser extent, the batteries in a hybrid add to their CO2 output during manufacturing, as well. This doesn't favor conventional gas-powered cars in any scenario, AFAIK, but in some states, a hybrid or plug-in hybrid beats an EV. As the power grid moves away from polluting sources, it looks better and better for EVs, of course.
One final point: Even driving an EV on 100% renewable energy carries
some environmental cost. There are wear-and-tear costs, like in tires, but also in other items. There's also the risk of wrecking the car, which will incur the major costs of manufacturing a replacement. These costs are smaller in an EV than in an ICE car, but still, no EV is truly "green;" they're just less dirty than ICE vehicles
. To further minimize your environmental impact, it's better to ride a bicycle or walk, whenever that's practical. Obviously, bicycling and walking aren't always practical, and I don't mean to scold anybody for driving; but it's worth considering the negative environmental impact of EVs, even though ICE vehicles are much worse.