Everybody in North America surely knows about the price sticker that is on a new vehicle. It has been there so long, normally attached on the passenger side window, that you might well have thought that it was something invented at the same time as the motor car itself.
For some reason the sticker is often called the Maroni, or even the Moroni, or Maroney. (All three are incorrect, with Moroni, for example, being the name given to the alleged angel that Joseph Smith claimed visited him and whose supposed likeness adorns the top of every Mormon temple pointing towards Salt Lake City.)
The name should be Monroney, named after Almer Stillwell “Mike” Monroney, who represented a congressional district in Oklahoma for twelve years, followed by eighteen years in the US Senate. And even when the name is gotten right the details are often incorrect. Sites like Wikipedia, that ubiquitous source of bad information, state that the sticker is required to give the recommended retail price of the base vehicle plus the option prices plus delivery charges, plus the fuel consumption data. The latter is incorrect. A dealer can be fined up to $10,000 for an omission or error in the Monroney’s pricing data but the consumption data is a later EPA addition to the sticker which carries no penalty for inexactitude. Dealers in the US have learned to take the sticker very seriously and a car cannot be delivered without an intact Monroney.
But what do we do with the EPA section of the sticker with the advent of the plug-in electric car (again!) and its indirect consumption of fossil fuels? The EPA has decided to invent a ‘miles-per-gallon equivalent’ (MPGe, sic) for consumer evaluation and has come up with an aggregate 99 MPGe (106 city, 92 highway) for the first electric vehicle to be deliverable, the Nissan Leaf. That immediately sounds like a dubious practice from an engineering definition, but let’s look at it more closely.
I was never too keen on some of the assumptions made in my thermodynamic classes (one of those compulsory interdisciplinary subjects in the first year of college) but the number that sticks in my mind for refined petroleum (gasoline) is that a US gallon (the shortchanged version at just 0.833 of an Imperial gallon – or 3.79 l instead of 4.55 l) represents the equivalent energy of 33.638 kW-hr at STP. You can derive this energy equivalence from the density of the fuel (0.73 g/ml) and thence its joules (1 US gallon is equivalent to about 121 MJ). And from there as 1 GJ is equivalent to 278 kW-hr, 1 US gallon is equivalent to 33.638 kW-hr. It would make more sense perhaps to take the energy equivalence of that US gallon of gas and compare it to engine horsepower (1 kW = 1.341 brake-horsepower) but the EPA has determined from its standard vehicle test runs, involving five different types of routes – that the Leaf uses an average of 34 kW-hr for every 100 miles (from the 99 MPGe with a 33.6 kW-hr/US gallon equivalence).
That sounds like some kind of chicanery to me but if you take their statement at face value then their next piece of the calculation shows some poor math skills: they say on the EPA sticker (small print at the bottom) that they base the $561 “Annual Electric Cost” on a vehicle use of 15,000 miles per year with an electrical cost of “12 cents per kW-hr” (I do appreciate their use of the correct unit in this case, unlike everybody else who wants to use, incorrectly, kWh). From the 34 kW-hr per 100 miles consumption that says that the vehicle will be using 5100 kW-hr for the 15,000 miles (34 x 150) which at 12 cents per kW-hr is a cost of $612. The $51 difference is difficult to fathom if it is not just bad arithmetic as it computes backwards to a MPGe of about 93 MPGe.
But why all this strange equivalence anyway? Surely the user is more concerned about the distance between charges of his vehicle to prevent being stuck at the side of the road? The sticker gives it as 73 miles based on a full charge of 7 hours at 240 V. Without a definition being given that is presumably based on the average five vehicle runs again; no doubt some drivers will obtain a higher mileage and some will obtain a lower one, depending on their driving techniques, traffic, and the terrain they cover. It is perhaps also important to point out the great negative about an electrical vehicle: it doesn’t matter how much charge there is in the on-board battery the vehicle weight remains a constant while a conventional gas-powered vehicle’s weight reduces as the fuel load decreases with consumption. A half-charged battery will not therefore get you a range of half of a fully-charged battery and any ‘distance to discharged’ gauge needs to take that into account for it to be accurate.
This mile-per-gallon equivalence is going to come back and bite the EPA when it tries to provide stickers for plug-in electric vehicles that also have a charging engine. The first such car is going to be the Chevrolet Volt. Strangely, on GM’s US site there appears to be no range number given for the Li-ion battery stack, although the Canadian site quotes an approximate range of 64 km (40 miles) with the charging engine extending that to “hundreds of km.” How do you translate the combination of electric battery plus generator into any kind of MPGe that makes sense for comparisons? Incidentally, the charging motor in the Volt is a 1.4 l engine of 80 hp (presumably bhp, but I tire of correcting units) that requires premium fuel!
The electric motor in the Volt is rated at 150 hp (which is 112 kW, and why rate an electric motor in hp?) compared to the 80 kW motor in the Leaf, and the Volt battery storage is 16 kW-hr compared to 24 kW-hr in the Leaf. Those numbers suggest, for about equal weights of vehicle, that the EPA typical route driving for the Volt, just on the initially-charged battery, is going to be about 35 miles – a little worse than Chevy itself is quoting.
While this is all playing out – probably badly for the EPA, and consumer sanity – it should be remembered that Senator Monroney was not only the chief sponsor of the Automobile Information Disclosure Act of 1958; he was also the sponsor of the creation of the FAA. It is to him that we owe the existence of modern day air traffic control in the world – a system that came out of the forced need for oversight during the Berlin Airlift when planes were landed at the then two airports in Berlin every three minutes (and later every two minutes), 24/7, for over thirteen months, all flying on instruments. Monroney deserves a great deal better than having his name butchered in the motor trade.
