## March 12th, 2007

### which is better, electric or gasoline?

35 kwh ~= 1 gal gasoline (need good source for this figure.)

35 kwh x 0.6kg CO2/kwh = 21kg CO2
1 gal x 8.8kg CO2/gal = 8.8kg CO2

gasoline would have less carbon footprint by this equivalence. However, it all depends on the first figure, which is from http://baltimorechronicle.com/2005/083005Korthof.shtml I need a better source for the expected range of this value.

update: If an electric engine is about 40% efficient, and a gas engine is about 15% efficient, then the figures are modified:

35 kwh x 0.6kg CO2/kwh = 21kg CO2 / 0.4 efficiency ratio = 52.5kg CO2
1 gal x 8.8kg CO2/gal = 8.8kg CO2 / 0.15 efficiency ratio = 59 kg CO2

So, with rounding errors and other losses, they're in the same order of magnitude in terms of carbon footprint.

update 2: If an EV gets between 2 and 6 miles per kwh, then

8.8 kg CO2 per gal / 20 miles per gallon = 0.44 kg CO2 per mile
8.8 kg CO2 per gal / 30 miles per gallon = 0.29 kg CO2 per mile
8.8 kg CO2 per gal / 40 miles per gallon = 0.22 kg CO2 per mile
0.6 kg CO2 per kwh / 2 miles per kwh = 0.3 kg CO2 per mile
0.6 kg CO2 per kwh / 4 miles per kwh = 0.15 kg CO2 per mile
0.6 kg CO2 per kwh / 6 miles per kwh = 0.1 kg CO2 per mile

I think I was led astray by the red herring conversion 35 kwh = 1 gal in the article. Converting to electric vehicle use depends strongly on the battery power and efficiency of conversion.

I'm very wary of figures I get from enthusiasts, since I know exactly how much my driving style can alter my fuel consumption on a variety of hybrid and non-hybrid vehicles. I also know that I can't always drive ideally.