Nissan Leaf to be rated at 99 mpg
Last updated Nov 22, 2010 — 3 views
Based on tests by the U.S. Environmental Protection Agency, the Nissan Leaf’s fuel efficiency window sticker will indicate an mpg equivalence of 106 mpg for city driving, and 92 mpg on highways, for a combined average of 99 mpg, according to news reports today.
“EPA’s tests estimate the Leaf can travel 73 miles on a fully charged battery and will cost $561 a year in electricity,” writes Ken Thomas in an Associated Press news item. “Nissan has said the Leaf can travel 100 miles on a full charge, based on tests used by California regulators.”
This is nearly double that of the Toyota Prius, which currently is rated at 50 mpg for combined city and highway driving, according to Thomas. GM, he adds, “has not yet revealed the mileage rating for the Volt.”
In an article published by the Wall Street Journal, Mike Ramsey notes that there had been some controversy regarding how electric vehicles would be rated by the EPA. GM initially said “the Volt might get the equivalent of 230 mpg, to which Nissan shot back that its Leaf would get the equivalent of 367 miles. However, “GM later retracted its estimate.”
According to Ramsey, the Leaf is the first electric vehicle to undergo “a new EPA rating system that tries to give gas-mileage equivalents for cars powered by alternative energy.” The EPA’s system is based on 33.7 kilowatt-hours of electricity being equivalent to a 100-mile range, reports Ramsey.
The Nissan Leaf and Chevy Volt are both expected to start showing up on North America highways by the first quarter of 2011.
An article in today’s 11/23/10 San Jose Mercury News noted that the EPA estimates it would take 33.7 kWh of battery storage for the Leaf to go 100 miles. With its 24 kWh, that works out to a range of roughly 70 miles. I did some calculations and found that 33.7 kWh is the energy content of 0.92 US gallons of gasoline, which works out to 75 mpg if the conversion were 100% efficient. At 25% efficiency (a guesstimate), it’s equivalent to 27 mpg. So how does Nissan get to claim 99 mpg? I suspect the EPA may be using the “mix” for electricity, with oil being only a small fraction. Plus, they may use a higher efficiency since electricity generation is significantly more efficient than a car’s gasoline engine. Anyone know for sure?
The discrepancy seems to be associated with the field tests by Nissan to measure typical range of the Leaf. A Wall Street Journal article provides an interesting discussion of the issue you’ve raised, and includes a quote from the manager of the Leaf’s U.S. launch.
Apparently, the California test range, used by Nissan to rate the Leaf, has been known to produce exaggerated range measurements. However, according to the WSJ story, “Nissan is sticking by its earlier estimates that in cold weather with the heater running the Leaf’s range could be as low as 62 miles, while in 70-degree weather in stop-and-go traffic, when the batteries are charged through the energy created by braking, it could be 138 miles.”
For more discussion on this point, read the WSJ story.