JoeS
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Posts: 3897
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

### Measured Wall-to-Wheels Consumption

After I first got my iMiEV it took me about a month to get the TED 5000 energy monitor up and working properly (had to return one of its modules). Since early March I've been meticulously recording the amount of energy drawn by my iMiEV, whether at home or at a public charging station (and I no longer opportunity-charge at friends' homes with the iMiEV).

Every once in a while I charge to 100% and I then add up all the intermediate charge amounts since the last 100% and figure out what the miles/kWh, kWh/mile, and kWh/100miles were for that interval. This is the actual wall-to-wheels energy consumption, but note the tire pressure caveat at the end of this discussion.

Happy to report the following summary of our everyday normal driving energy consumption for 2 March through 13 May. If you're a purist, you can round off appropriately and recognize that the TED monitor is a consumer product (but it was within 1% of my Kill-A-Watt), and the mileage is off the iMiEV's odometer (which is also within about 1% of the GPS):

Miles driven: 1937.3
Energy consumed: 442.813kWh
Yielding:
4.375miles/kWh
0.2286kWh/mi
22.86kWh/100mi

Which is significantly better than the 30kWh/100mi (27 City, 34 Highway) EPA Monroney sticker.

Using the EPA's conversion of 33.7kWh/gallon, this would yield 147.4MPGe. Not too shabby, even if I disagree with their metrics.

Now, with this information, if you know how much you're paying for electricity in cents/kWh and if you know how much you drive per month or year, you can quickly figure out what your monthly or yearly costs are.

For example, if I didn't have solar and had to pay the going rate for my off-peak (PG&E E-7) of \$0.08/kWh, this would yield 0.08*0.2286 = 1.8 cents/mile! If we compare this to a subcompact that gets 30mpg, with gas costing \$4.50/gal around here nowadays, that subcompact's fuel costs would be 4.50/30 = 15 cents/mile. Fair to say that our iMiEV's "fuel" cost is an order of magnitude less than an average US vehicle.

Some more tidbits from my data-taking:

Best Range Remaining (RR) after top-up: 98 miles
Worst RR after top-up: 57 miles
Best energy use recorded: 5.32miles/kWh (18.8kWh/100mi) over 113.2 miles
Worst energy use recorded: 3.64miles/kWh (27.5kWh/100mi) over 87.5 miles

The EPA says that the iMiEV's all-round range is 62 miles. By comparison, if I arbitrarily say that our 16kWh battery has an effective usable non-stressing capacity of, say, 14kWh, this would mean for us this averages out to a non-stressing range of 14*4.375 = 61.3 miles ... I just calculated this and, frankly, am surprised that it's so close to the EPA number. In case you're interested, full capacity would be 16kWh*4.375mi/kWhr=70miles.

These numbers come from a combination of my wife's driving (she's a featherfoot) and my own, which ranges from unabashed leadfoot to hypermiling depending on how far I'm going on any particular trip. Average springtime temperature probably around 65degF and altitudes ranging from sea-level up to 2000'. I would guess an overall 50/50 mix of city/highway - sorry I'm not more accurate, as this is the major consumption determining factor. The only "modification" to the car is that I'm running the tires at 55psi, as I perceive that this not only improves mileage but handling as well (I run high tire pressures in all my cars).

Hopefully this puts some mileage speculation to bed. If anybody wants, I can publish the summary spreadsheet as well. I'll occasionally update this as I'm still diligently recording the consumption.

Finally, as they say, YMMV.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

fjpod
Posts: 529
Joined: Tue Apr 17, 2012 2:31 am
Location: NYC

### Re: Measured Wall-to-Wheels Consumption

Thanks for those stats. I've only had mine three days, and I am planning on tracking my electric usage with a Kill-a -watt until I can establish some norms.

tonymil
Posts: 274
Joined: Mon Apr 16, 2012 6:50 am
Location: Latham, NY

### Re: Measured Wall-to-Wheels Consumption

JoeS,

This is great stuff, thanks! I don't know if I've shared this on this forum before, but the Union of Concerned Scientists just came out with a report entitled "Electric Vehicles’ Global Warming Emissions
and Fuel-Cost Savings across the United States". You can find the report here:

They used an assumed ev efficiency of .34 kwh per mile, so your numbers show that in reality a MiEV reduces greenhouse gas emission much more dramatically than the report estimates. I live in upstate NY, one of the "best" places to switch to an ev. I'm picking up my MiEV this Friday and really looking forward to it.

Tony

JoeS
Site Moderator
Posts: 3897
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

### Re: Measured Wall-to-Wheels Consumption

tonymil, I'm still wading through the UCS report and their new metric of MPGghg. Yes, my iMiEV is running closer to 23kWh/100mi instead of their assumed 34kWh/100mi.

Now that I've covered over 4100 miles, time for an update since I started my methodical datataking -

Miles driven: 3058.3
Energy consumed: 714.856kWh

Yielding:
Average 4.2782miles/kWh
Median 4.2080miles/kWh
Average 0.2337kWh/mi
Median 0.2376kWh/mi
Average 23.37kWh/100mi
Median 22.76kWh/100mi

This shows that we continue to consistently significantly beat the average EPA rating of 30kWh/100mi.

Best Range Remaining (RR) after top-up: 98 miles
Worst RR after top-up: 48 miles
Best energy use recorded: 5.32miles/kWh (18.8kWh/100mi) over 113.2 miles
Worst energy use recorded: 3.37miles/kWh (29.66kWh/100mi) over 34.9 miles

All the comments in the first entry of this thread still apply, although one of the datapoints was when I opportunity-charged at a friend's house not using a meter, but I recorded the exact amount of time I was plugged in with my EVSE and measured the voltage so the scaled/derived energy input for that session I feel was quite accurate. If anyone wants a copy of the spreadsheet with the data summary just send me a PM.

The only caveat is that I am now running 60psi in the tires instead of the specified 36psi.

This should give any prospective iMiEV owner a reasonable idea of what your operating costs would be as all you need to do is know your electricity cost. For example, say your electricity cost is ten cents / kilowatt-hour, then

0.10 * 0.234 = 2.3 cents/mile 'fuel' use
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

tonymil
Posts: 274
Joined: Mon Apr 16, 2012 6:50 am
Location: Latham, NY

### Re: Measured Wall-to-Wheels Consumption

Fantastic numbers JoeS. Even your worst calculated energy usage, 29.66kWh/100mi or .30kWh per mile, is better than the UCS assumed efficiency of .34kWh per mile. Whenever I tell someone about the MiEV, the eyes stop rolling and they become very interested once I tell them how much money I'm saving by not using gas. But for me, the reduction in carbon footprint is just as important and each reduction in kWh per mile is further reduction in carbon beyond what's in the UCS report. Great stuff.

JoeS
Site Moderator
Posts: 3897
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

### Re: Measured Wall-to-Wheels Consumption

At the end of 5154 miles yesterday, time for an update since I started my methodical datataking -

Miles driven: 4095.6
Energy consumed: 959.428kWh

Yielding:
Average 4.2688miles/kWh
Median 4.1765miles/kWh
Average 0.2343kWh/mi
Median 0.2394kWh/mi
Average 23.43kWh/100mi
Median 23.94kWh/100mi

All the caveats of my 6/15/12 posting (above) apply and haven't beaten my worst/best records. My new 240vac wattmeter and my old Kill-A-Watt corroborate the T.E.D. readings pretty well.

I'm beginning to suspect that the EPA ratings do not take regen properly into account ... need a separate thread to discuss this.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

joev
Posts: 53
Joined: Sun Jul 01, 2012 3:07 am
Location: Long Island, NY

### Re: Measured Wall-to-Wheels Consumption

Thanks JoeS! Your numbers look a lot like mine. I only have about 300 miles so far but I will post when I get more data under my wheels. I have an excel spread sheet full of (useful / useless, can't decide) information. Good to have a comparison!

PlugWiz
Posts: 5
Joined: Tue Jul 24, 2012 2:49 pm

### Re: Measured Wall-to-Wheels Consumption

JoeS wrote:After I first got my iMiEV it took me about ...

Now, with this information, if you know how much you're paying for electricity in cents/kWh and if you know how much you drive per month or year, you can quickly figure out what your monthly or yearly costs are.

For example, if I didn't have solar and had to pay the going rate for my off-peak (PG&E E-7) of \$0.08/kWh, this would yield 0.08*0.2286 = 1.8 cents/mile! If we compare this to a subcompact that gets 30mpg, with gas costing \$4.50/gal around here nowadays, that subcompact's fuel costs would be 4.50/30 = 15 cents/mile. Fair to say that our iMiEV's "fuel" cost is an order of magnitude less than an average US vehicle.
.

JoeS - trying to resurrect this topic and hoping you might take a look at this web tool in beta mode to help current and more importantly, potential EV owners estimate their costs to drive on electricity:

We are hoping for feedback so we can refine and bring it to the masses. Thanks for the consideration.

JoeS
Site Moderator
Posts: 3897
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

### Re: Measured Wall-to-Wheels Consumption

At the end of 6230 total miles (10026km) yesterday, time for an update since I started my methodical datataking. Since the average and median numbers are so close, I'm not bothering to post the median readings any more, and you can round off the numbers as you see fit.
For the benefit of the rest of the world, I'm now including kilometers as well (a change the US should have implemented a century ago!)

Distance driven with measurements: 5171.1mi (8322.1km)
Energy consumed: 1216.055kWh
Yielding:
Average 4.2524miles/kWh (6.8435km/kWh)
Average 0.2352kWh/mi (0.1461kWh/km)
Average 23.52kWh/100mi
Average 14.61kWh/100km

All the caveats of my 6/15/12 posting (above) apply and I haven't beaten my worst/best records.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

joev
Posts: 53
Joined: Sun Jul 01, 2012 3:07 am
Location: Long Island, NY

### Re: Measured Wall-to-Wheels Consumption

Not a lot of miles yet but this is what I have so far:
428 miles (689km)
79kWh used
80% of the driving is 20-35 mph (32-56 kmph).

Average 5.4miles/kWh (8.7km/kWh)
Average 0.185kWh/mi (0.116kWh/km)
Average 18.46kWh/100mi
Average 11.56kWh/100km

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