The car tells you your driving efficiency, 4 miles per kwh stored in the battery is pretty reasonable. The nominal 24 kwh battery capacity really means about 21 kwh useable capacity, and conveniently 4 miles / kwh * 21 kwh = 84 miles, the EPA range.Also - I'm not following where your 4 miles per kwh are coming from.
90% charging efficiency means 1 kwh at the wall socket gives you 0.9 kwh in the battery. So 4 miles / (kwh in the battery) means 3.6 miles / (kwh from the wall socket).Regardless the 90% efficiency of the charger has nothing to do with the co2 produced for the generation of the power.
Yes, if your electric grid is 100% driven by coal, the Leaf seems to match the Honda Fit in CO2 per mile via this simple calculation.So roughly the same amount of co2 into the environment in this example.
So with that being said even if these numbers were correct I'll buy a Honda Fit for half the price of a Nissan Leaf 100% of the time.
Except the factors we ignored, like the energy costs of refining gasoline versus transporting coal, are all worse for gasoline. Plus nobody's grid is 100% coal, there will be at least some lower carbon sources mixed in. California is already less than 10% coal.
So right now, the Leaf wins on CO2 pollution. And in 5 or 10 years, when the grid is even less CO2 based, that Fit will still be polluting the same amount of CO2/mile, while the grid-powered Leaf has improved.
Or you can buy solar panels when you buy your Leaf, and potentially get to near zero CO2/mile (just the manufacturing footprint of the panels).