Correction: Nissan Leaf Actually Gets 28 MPG

egg In a previous post, DbC reported that the miles-per-gallon performance of the Nissan Leaf was 38. Turns out this was a major over-estimate, as explained by physicist Tom Murphy.

If one focuses, as the peddlers of the things push and count on us to do, only on the charge-to-wheels aspect of the question, the numbers look very good. Murphy’s explanation:

How do electric cars or other electric/hybrids stack up? In order of performance: the Chevy Volt gets 35 miles from a 16 kWh battery for a consumption of 45 kWh/100-mi; the Nissan Leaf gets 73 miles from its 24 kWh battery for 33 kWh/100-mi; and the pricey Tesla has a 244 mile range using a 53 kWh battery, for 22 kWh/100-mi. The MPG equivalent of these three figures is approximately 80, 110, and 170, respectively. All are much better deals than gasoline cars deliver, primarily because the electrical drive system is far more efficient than the typical 20% gasoline engine.

The reality, though, is that charge-to-wheels is only half the process. What about production-to-charge, or the question of what it takes to put the power into the so-called electric vehicle’s battery? Murphy again:

In order to deliver 30 kWh to your house to fully charge the Leaf’s 24 kWh battery bank, for example—incorporating the charge efficiency this time, the source of electricity becomes a highly relevant factor. Two-thirds of our electricity comes from fossil fuel plants, typically converting 35% of the fossil fuel thermal energy into electricity. Only 90% of this makes it through the transmission system, on average. If your electricity comes from a fossil fuel plant, the 30 kWh delivered to your house took about 95 kWh of fossil fuel energy. The 73 miles the Leaf travels on a full charge now puts it at an energy efficiency of 130 kWh/100-mi. The MPG equivalent number is 28 MPG. From a carbon-dioxide standpoint, you’d be better off burning the fossil fuel directly in your car.

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