Gasoline engines are (like Da Dude says) about 25% efficient. It varies, though. TDI diesel engines are notably higher. A typical coal-burning power plant is in the 30%-40% range. Globally, the average is 33%. The newest, greatest supercritical coal plant is 46% efficient. The electrical grid is "pretty efficient". Nationally, about 6%-7% of the electricity generated is lost in transmission/distribution. So efficiency is >90%. The problem is, that coal figure based on how much of the heat of burning it is used. The difference is gasoline is MUCH denser energy-wise and has more energy per lb and you get more energy per lb of CO2 generated.

ELI5: If we all suddenly started driving Teslas, wouldn't the corresponding electricity demand (and coal burning) negate any positive effect of the drop in vehicle emissions? : explainlikeimfive Monday, December 23, 2013 @ 7:03pm