We have a new winner in the MPGe brawl: Honda’s new all-electric 2013 Fit can go 118 miles on a gallon of imagined gas, measurement brought to you by your tax dollars and the EPA. Chevrolet meanwhile tweaked battery and electronics of its range-extended Volt for four miles more on the MPGe scale (95 to now 98, combined), and a slightly better electric range of 38 miles. The perception of customers remains conflicted. After all, they wanted to escape gas, and now they have to contend with simulated gallons. That’s just the beginning of the plug-in perplexity.
The electric leaderboard now looks like this:
| EPA MPGe | |||||
| Rank | Manufacturer/Model | Comb | City | Hwy | E-Range |
| 1 | Honda Fit EV (electric) | 118 | 132 | 105 | 82 |
| 2 | Mitsubishi i-MiEV (electric) | 112 | 126 | 99 | 62 |
| 3 | Ford Focus Electric (electric) | 105 | 110 | 99 | 76 |
| 4 | Nissan Leaf (electric) | 99 | 106 | 92 | 73 |
| 5 | Chevrolet Volt (plug-in hybrid) * | 98 | 101 | 98 | 38 |
| 6 | Coda Coda (electric) | 73 | 77 | 68 | 88 |
| 7 | Azure Dynamics Transit Connect Electric Van/Wagon (electric) | 62 | 62 | 62 | 56 |
| * upgraded 2013 model, total range 380 miles | |||||
The compilation of this table wasn’t easy. There is no single table that provides the information above. The EPA supplies conflicting information. GM does not supply the new city and highway numbers, we have to take Autobytel’s word for the data.
Speaking of conflicting data, having the Department of The Treasury as a co-owner does not guarantee preferred, or even fair treatment. A search of the EPA’s website for the official MPGe data provides the above. According to the EPA, the Volt has a combined MPGe rating of 60.
Once you head over to the government-supplied fueleconomy.gov, the MPGe rating jumps to 94 (combined) for the 2012 model. Are we confused yet? No? Ok, how about this one:
Based on alleged “real world MPG estimates,” the Volt can get anywhere between 30 and 1462 MPGe, for an average of 167.1 MPGe. I tried to contribute to the crowdsourced data and help GM by adding a few stellar MPGe “measurements.”
However, my true readings were rejected by a “The MPG is larger than expected” error message.
If my 1420 are not good enough, then why is the list crowned by three allegedly valid measurements that are higher than 1420 mpg? Why does the government specify the Volt’s mileage as 60 MPGe, then as 94 MPGe, then as up to 1462 MPGe? Why does it invite obvious fakery that drives the MPGe into the stratosphere? Why am I locked out from contributing to the fakery?
Ah, the numbers business. I feel for the poor muck who was forced into putting those numbers down on paper by his superiors.
Pretty soon we’ll have politicians bragging about how many Jobs-e they’ve created…or how they’ve cut taxes such-and-such %-e…or they’ll cut our fossil fuel consumption in half by 2022e.
…or jobs “created or saved.”
It isn’t confusing.
Why does the government specify the Volt’s mileage as 60 MPGe, then as 94 MPGe, then as up to 1462 MPGe?
– That’s obvious. The Volt in full gas mode gets combined 30s mpg. In full electric mode, it gets combined near 100 mpge. Combine (again) those two under certain assumptions of driving gives you ~60. As always, YMMV. That number passes the smell test so it seems reasonable depending on how (far) you drive at a time. (Since my commute is short, my mileage would be closer to the 100 mpge because I would rarely engage the gas generator. People with 100 mi hwy commutes would be much closer to the 30s mpge number.)
The 94 mpge figure is not ‘published’ by anyone and the govt doesn’t claim it. Rather, it is a dumb, automatic calculation on a website that relies on people entering sensible information. I would say there’s more than a small chance that people are entering info based solely on gasoline and not including electricity, hence the stupid numbers well over 1000 mpge. I expect their IT folks noticed the same thing as you and installed a filter on the data. The data that’s already in there stays, but it won’t accept any new unreasonable values.
If you actually want to dig into some data and find some confusing discrepancies, do this: Compare efficiency, range, and battery size of each of the listed cars. Then, reconcile them. You would expect range = battery size * mpge (1 gal equiv = 33.07 kWh), but a quick check shows that doesn’t match up. I’ve already run the numbers for eFit, i-MiEV, eFocus, & Leaf:
eFit: to go its 82 mi range should need 23.4 kWh of electricity, but it has a 20 kWh battery.
i-MiEV: 62 mi range needs 18.7 kWh from a 16kWh battery
eFocus: 76 mi range needs 24.4 kWh from a 23 kWh battery
Leaf: 73 mi range needs 24.9 kWh from a 24 kWh battery
I don’t know if the range numbers are distance to ‘brick’ or if there is a certain reserve left in the battery, which makes the effective battery size smaller than the published values.
My first guess to explain the discrepancies is that the published mpge numbers include charging inefficiencies, e.g., it takes more than 20 kWh of electricity to fully charge a 20 kWh battery. If so, the numbers for the eFit & i-MiEV seem right with charging efficiencies of ~85%. But the eFocus & Leaf have efficiencies of ~95%. Since heat is generated during charging (and the eFocus even has a cooling system to prevent heat damage during charging), their number seems high. Also, different types of charging likely have different efficiencies: it would seem that fast charging would be less efficient than regular charging, and using a 240 V outlet would be different than 110 V.
And perhaps the most confusing thing of all: Why is “Leafs” the plural of “Leaf”? Why not “Leaves”? Do they have some sort of corporate tie-in with the hockey team?
There will be charging losses and inefficiencies like you mentioned, but you completely forgot about the vehicles regenerating power on their own when braking. Obviously that won’t be 100% efficient either, but it allows a total higher than the capacity of the battery pack if you’re concerned about net power. More data is needed for your calculations to be worthwhile, especially where none of them will let the battery drain completely (which will shorten it’s life).
Regen from braking is effectively just more efficient city driving. The MPGe metric only examines power at the wall vs total miles driven, closed loop energy shuffling via regen is inconsequential.
The EPA rated MPGe of electric cars takes into account the inefficiency of charging the battery pack from shore power.
MPGe is indeed calculated at the wall, and the quoted figures do count those losses.
Some of the difference in efficiencies is probably due to the car restricting how much battery is being used. For example, the MiEV may do a 100% discharge of its battery (I don’t know); but the Leaf may only do a 90% discharge. 16 kWh battery charge / 18.7 kWh wall = 86% efficient, 24 kWh * 0.90 / 24.9 kWh wall = 86.7% efficient.
http://www.mynissanleaf.com/viewtopic.php?f=8&t=8266
(SOC seems to be 95% to 5% turtle, the turtle may well terminate the EPA test)
220V charging is *generally* a bit more efficient than 110v.
With $4 gas, the cost difference between 100 mpg and 1000 mpg over 10,000 miles is $360. Big deal.
These ultra-high mpg numbers are meaningless, and subject to the smallest changes in the many variables governing them. Critics claim the mfrs “lie”, while hypermilers double or triple the EPA numbers.
Thats $3600 over 100,000 miles, so for high-mileage 20k/year drivers that’s $720 a year. Or $60 a month, which is nothing to sneeze at. That’s the price of a premium cable package, or a monthly maid, both of which people sneer at as luxuries. My point being, for some people, it will benefit them.
mpg figures matter in comparison to their proportionality to each other. A 100 mpg will cost 1/3 as much to fuel as a 33 mpg car. A 1000 mpg car will cost 1/10 as much to fuel as a 100 mpg car. If you are only spending $60/mo on fuel, any reduction isn’t going to be that big of a boon, but if you spend $400/month, even a 10% improvement is good.
If electricity costs comparible to gas (which it is right now because $0.10/kWh = $3.37/gal equiv), then a 100 mpge EV will cost about a third to fuel as a 30 mpg gas car. If gas prices spike, the cost difference increases. I don’t consider that difference to be trivial, but it still would take near 100k mi to recoup the price premium.
It’s confusing, but there is no conflict.
To make it simple, let’s stick with the 2012 Volt.
– MPG for gas only: 35 city/ 40 highway/ 37 combined
– MPGe for electric use only: 95 city/ 93 highway/ 94 combined
– Combination MPG of gas and electricity: 58 city/ 62 highway/ 60 combined
Note the difference. The higher MPGe figures are electric, the lower ones are a blend of gas and electric. The EPA seems to be assuming that the gas engine is in use a bit more than 50% of the time — how they arrived at that figure, I don’t know.
Meanwhile, GM is promising some improvements for 2013: http://media.gm.com/media/us/en/gm/news.detail.html/content/Pages/news/us/en/2012/Jun/0607_volt.html As of now, the EPA hasn’t put the data from this on its website.
It might be easier for consumers if they took the average prices for gas and electricity and simply calculated the cost per 100,000 miles of mixed driving. That would give consumers a leg up in determining whether to pay the premium for a hybrid or electric car.
*cough* coal fired electric plants to charge Ev’s *cough*
*cough* Smart Grid *cough*