>"I’ve looked up the performance figures for lots of electric vehicles – they’re listed in this chapter’s end-notes – and they seem to be consistent with this s

>"I’ve looked up the performance figures for lots of electric vehicles – they’re listed in this chapter’s end-notes – and they seem to be consistent with this summary: electric vehicles can deliver transport at an energy cost of roughly 15 kWh per 100 km. That’s five times better than our baseline fossil-car, and significantly better than any hybrid cars. Hurray!" I'm surprised MacKay said this, as it's misleading to compare heat energy (the heat content of a liquid fuel) with electric. That "five times better" figure basically comes from shifting the combustion of fossil fuel (and its thermodynamic losses) from the car to the power plant -- it's an artifact of the definition. In fact, based on the EPA's Chevy Volt numbers (which may or may not be representative), it could be more efficient to burn gas in the Volt, than fossil fuel in a power plant for its electric engine. How I figure: 37 mpg on gas means 2.70 gallons/100 miles = 348 megajoules/100 miles (energy density of gasoline is 34 MJ/L [1]) On the electric side, it uses 36 kWh (130 MJ) electricity/100 miles. According to EIA figures, average US power plant efficiencies are [2]: * for oil, 31% efficiency --> Volt uses 418 MJ power plant oil/100 miles * for coal, 33% efficiency --> Volt uses 394 MJ power plant coal/100 miles * for natural gas, 41% efficiency --> Volt uses 315 MJ power plant NG/100 miles The CO2 emissions on electric are lower in the Volt, not because of an efficiency advantage, but because some of the electricity sources (hydro, nuclear) aren't fossil fuels. Likewise, the cost/mile is usually lower because the per-Joule cost of coal and natural gas are far lower than that of oil and gasoline. [1] http://en.wikipedia.org/wiki/Energy_density http://en.wikipedia.org/wiki/Energy_density [2] http://www.eia.doe.gov/aer/txt/ptb1306.html http://www.eia.doe.gov/aer/txt/ptb1306.html