The Economist explains
THE most remarkable thing about the new Nissan Leaf—the world's first fully electric family car to go into mass production—is that it is so utterly unremarkable. It looks like an ordinary motor car. It rides and handles like one (as a prospective buyer, your correspondent took one out for a spin last week). It accelerates briskly and stops just as assuredly as a conventional vehicle. It accommodates five adults with as much ease or squeeze as any other family runabout. And it gets the equivalent of, er, let's just say “probably more” miles per gallon than a comparable fossil-fuel car or conventional hybrid.
The powers that be have yet to agree on how to compare electric cars with conventional ones. That makes it difficult for consumers to work out how much money, if any, they will save on annual fuel costs by buying a pure electric vehicle like the Leaf instead of a plug-in hybrid such as the forthcoming Chevrolet Volt (to be called Ampera in Europe)—or even a conventional hybrid like the Toyota Prius, let alone one of the new clean diesels such as the Volkswagen TDI.
For the past 30 years, the first thing American motorists have done when kicking the tyres in car showrooms has been to check the official “Monroney sticker” affixed to one of the vehicle's windows. Amongst other things, this lists the miles per gallon (mpg) the model achieves when tested on the Environmental Protection Agency's simulated city and highway driving cycles. The label also shows how the model's combined city/highway fuel economy compares with a range of broadly similar vehicles. In addition, the label lists the estimated fuel cost of operating the vehicle for a year. Nowadays, the mpg figure for the combined cycle is usually pretty close to what most motorists can expect to achieve in everyday motoring.
But today's sticker is meaningless when vehicles get at least some, if not all, of their energy from a plug on the wall rather than a pump at the petrol station—as is the case with pure electrics like the Leaf and plug-in hybrids such as the Volt. (The company prefers to call the Volt an “extended-range electric vehicle” because its petrol engine cannot drive the wheels directly like a Prius's can, but generates electricity to do so instead.)
For the past couple of years, the Environmental Protection Agency and the National Highway Traffic Safety Administration have been collaborating on a new design for the car sticker. The revised label, required under the Energy Independence and Security Act of 2007, is to provide additional information on fuel economy and emissions over the vehicle's lifetime, along with a rating scale designed to help consumers compare makes and models at the point of purchase. It will also take into account the needs of people purchasing vehicles that get their energy from the grid rather than the pump.
Unfortunately, the redesigned sticker is still stuck at the discussion stage. Manufacturers hate the idea of new cars being rated (like school grades) with the letters A+ to D, based on their fuel consumption and emission of greenhouse gases. They argue that such a scheme would stigmatise large vehicles (D grade), while giving an unfair advantage to plug-in electrics (A+ grade) by ignoring the emissions produced by the coal-fired power stations that will be used in most parts of America to recharge such vehicles at night. One way or another, the new sticker—whether based on a letter grade or some variation of the existing label—has to be ready for the 2012 model year.
Meanwhile, people thinking about buying an electric car or a plug-in hybrid are being left in the dark. “There's a lot of obfuscation,” says Dan Edmunds, director of vehicle testing at (no relation) Edmunds.com, an independent car-pricing and evaluation group based in Santa Monica, California. “Because of charging losses, you don't know how much electricity you are actually putting into the battery,” he notes. Nor do you really know how much of the battery's rated capacity (24 kilowatt-hours for the Leaf) is useable. “That's a trade secret,” says a frustrated Mr Edmunds.
Compounding matters, it is difficult to find out exactly how much the electricity used to charge the battery costs, given the various rates charged by power companies at different times of the day, in different parts of the country. It is certainly not the 11 cents a kilowatt-hour quoted widely by electric-vehicle makers. With their limited range, electric vehicles are going to be used predominantly in large urban areas—precisely where electricity rates are the highest. In the tri-state area around New York, for instance, electricity costs over 20 cents a kilowatt-hour. Add the impact that high and low temperatures have on an electric vehicle's range, and the cost of running a plug-in car becomes almost anyone's guess.
Engineers at Argonne National Laboratory in Illinois have at least made a stab at it. Their dual-test proposal has recently been adopted by the Society of Automotive Engineers (SAE) for testing conventional hybrids like the Prius and plug-in hybrids such as the Volt. The revised sticker is expected to be based, at least in part, on this new SAE standard. In the meantime, the Argonne engineers are developing a comparable procedure for testing pure electrics like the Leaf.
That ought to be simpler. By contrast, hybrid cars have to be tested in two different ways—once when using just the petrol engine, and once when the vehicle is running solely on battery power. The two sets of results then have to be combined using a weighting factor that takes into account the vehicle's range on electric power alone relative to the average distance motorists in America drive a day (around 35 miles, or 56km).
This so-called “utility factor” is expected to be quoted on the new sticker for hybrids (plug-in or otherwise), along with the watt-hours consumed per mile when driving on battery power, plus a separate mpg figure for when a hybrid is using just its petrol engine. Pure electrics will probably display just the watt-hours per mile and perhaps some variation of the utility factor.
Even so, such gobbledegook is hardly going to make life easier for motorists thinking of buying a plug-in. Your correspondent believes plug-in cars (whether pure electrics or hybrids) should display an equivalent of the combined cycle used for conventional cars. That is what consumers understand and expect. Besides, it is not all that difficult to compute. There are 33,700 watt-hours of energy in an American gallon of petrol. So, if a Nissan Leaf uses, say, 300 watt-hours to travel a mile, then its equivalent fuel economy in petrol terms would be 112mpg.
Of course, that represents only the energy stored in the vehicle's battery, not what is drawn from the plug—still less what has to be generated at the power station to deliver that level of performance over the grid to the car. Taking such losses into account, using the Department of Energy's "lumped efficiency factor", would reduce the Leaf's petrol-equivalent consumption to a net 34mpg. But, then, the fuel economy figures printed on the existing stickers for conventional cars do not represent the vehicle's true well-to-wheels consumption either. To insist on one, and not the other, would be ridiculous. As flawed as it may be, at least a simple mpg equivalent figure on the window of a Leaf or a Volt would let consumers quickly see how much they might save by going electric. A lot more might then choose to do so than if left to deal with unfamiliar watt-hours rather than friendly old miles per gallon.