First EV Electric bill mi/kWh $/mi numbers

Ok...my first electric bill arrived today:

I used 281 kWhs in 20 days and drove 906 miles.

Electric bill WITH taxes was $37.37.

Breakdown:
8kWh On-peak
152kWh Off-peak
121kWh Super off-peak
(I can and will improve these numbers by using the charge timer more effectively)

These numbers average out to $.04/mi and 3.22 mi/kW (this is wall-to-wheels efficiency), and makes the equivalent of $1.40/gallon of gas, when compared to a 35mpg car.

Those same miles in my Escape Hybrid would have cost approx. $90 in gas. I was hoping for a little more efficiency, so I have my work cut out for me.

Discuss.

Interestingly your overall cost per kWh worked out pretty close to normal tier 1 non-TOU DR rates (.138) - but it probably wouldn't be tier 1 for someone without solar since it would be on top of the house usage.

With your EVSE generally pulling at 3.7kW (?), those 281 kWh presumably took about 75 hours. And in the 20 days you had 20 x 5 or 100 hours of
super-off-peak available, so in theory you could have obtained all the charging during super-off-peak, assuming no one day of charging
required more than 5 hours, but that may not quite be achievable on commute days...?. If you could get it (almost) all done in super-off-peak,
maybe you could get the bill down closer to $20 (281 x .07) or at least under $25 with taxes, and you'd be below .03/mile from .0412.

Jimmy, it appears from my TED data that the car allows 6 hours to recharge, whether it needs it or not. In my case, using only a charge stop timer and 80% charging (typically 33% to 83% SOC), it is starting six hours before the end time I set, and actually charging for just under three hours. Shouldn't be too difficult to play with timers and move charging into the super off-peak sweet spot...

-Karl

Having the last two hours (the two "EQ" wait-n-pulse periods) occur after the 12 midnight to 5 AM super-peak window (if necessary) would seem to be optimal, right?

So, start-timer charging shortly after midnight would seem optimal, right?

Jimmy,
Did (or will) the EV-TOU charge get offset in any way by your PV bill?

Can you make sense of your PV-House "true-up" bill?

garygid said:

Having the last two hours (the two "EQ" wait-n-pulse periods) occur after the 12 midnight to 5 AM super-peak window (if necessary) would seem to be optimal, right?

So, start-timer charging shortly after midnight would seem optimal, right?

Jimmy,
Did (or will) the EV-TOU charge get offset in any way by your PV bill?

Can you make sense of your PV-House "true-up" bill?

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I will try and start charging as late as possible to maximize my super-off peak time. We shall see.

The EV is on a separate TOU meter for at least 12 months. After that time, I'll be able to crunch the numbers and see how those rates compare to regular home rates with my solar.....I'll go with whatever is cheapest on average for the year.

As for my true-up bill....not really. It's confusing and you pretty much have to take them on faith that the numbers are correct. My true-up bill should be in my mailbox this week. Can't wait to see it..... :?

Jimmydreams said:

The EV is on a separate TOU meter for at least 12 months.

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Jimmy,

I believe the tariff is being revised now from 12 to 24 months.

Malcolm

An interesting article on the dollar cost and carbon cost of driving for an EV, Hybrid, and conventional ICE car.

http://homepower.com/article/?file=HP141_pg16_OnTheRoad

We just got our first full month solar and car too - 12/29-1/30. Actually, it's minus about a week of car use because I didn't get it until the 5th. But irrespective of, the numbers seem to come out where I'd expect them.

Now bear in mind that we're just on the one meter and I don't have the TED or anything, so it's hard to break it out with massive accuracy. But the solar production between meter reads was 590kWh (and I loose some in the inversion process, right?). Then I used the car for 11 days for work, and figured 18-20kWh per day for that, so another ~200kWh (plus maybe another 20kWh for the other running around on weekends and stuff). Then the meter read was 130kWh different from what it was at the end of last month and our typical January usage has been 500-550kWh.

Pleased overall, but am still aching to see my first months negative use, car and all!

mwalsh said:

But the solar production between meter reads was 590kWh (and I loose some in the inversion process, right?).

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The numbers from your inverter should be for AC production (after DC->AC conversion), so any losses should be included. Most inverters tend to read a bit high - often up to 5% or more as they don't account for night-time tare losses (all inverters draw a small amount of power at night) and just tend to overestimate a bit.

A revenue grade meter is the only way to be sure as these are certified to be accurate to well under 1%.

The TED has been known to be off by as much as 10-15% as well in some cases.

just got mine yesterday...posted it on PC so here it is.

now its up to Feb 2nd and what you cant see is change from last year and it said i used 200 KWH more. on my records per my KAW, i used 200.62 KWH. so i guess that goes a long way towards verifying the accuracy of that.

now, i had my Zenn last year but this was also first winter with 2010 Prius so was in middle of experiment with grill blocking so did not drive Zenn from Dec to Mar last year. (also had batt issues which was discussed in another thread)

My first EV electric bill arrived today...

It is from 1/12 through 2/1. I used 83 kWh, and it was ALL in the Super off-peak timeframe (midnight to 5am). Even though I know I did all of my charging during that timeframe, I was expecting some Clipper Creek vampire watts during the other periods, but they showed zero.

The charges were $2.33 for the electricity itself, $.42 for the DWR bond charge, $3.10 for generation, and $0.38 for City of San Diego franchise fee, State surcharge tax and State Regulatory fee, for a grand total of $6.23. They did subtract the 83kWh from the house meter read correctly.

Using my Carwings spreadsheet logs for mileage I drove during that time, I show 322.1 miles or about 3.88 kWh per mile measured from the meter to the wheels.

The interesting thing is that my Carwings spreadsheet electricity consumption almost matches the meter read for that period. I was billed for 83 kWh and Carwings shows 84.4 kWh of electricitiy used (consumption). If you factor in the small amount of time I was plugged in at Malcolm's when our cars were detailed, we figured I got about 1 kWh from him. That is almost a perfect match between Carwings electricity used (consumption) vs. what I was billed for. I'll be keeping a closer eye on those numbers in the future...

So 322 miles for $6.23 equals 1.9 cents per mile...Not too shabby...My previous car got around 25-30 mpg, so that would have been around 11.7 gallons of premium unleaded if you split the difference at 27.5 mpg. To buy that gas today would cost 11.7*3.55= $41.56 for the same 322 miles. Turns out the EV fuel is about 15% of what I would have paid for gasoline....

I'm very pleased....

Randy

Randy said:

The interesting thing is that my Carwings spreadsheet electricity consumption almost matches the meter read for that period. I was billed for 83 kWh and Carwings shows 84.4 kWh of electricitiy used (consumption). If you factor in the small amount of time I was plugged in at Malcolm's when our cars were detailed, we figured I got about 1 kWh from him. That is almost a perfect match between Carwings electricity used (consumption) vs. what I was billed for. I'll be keeping a closer eye on those numbers in the future...

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Very interesting. We have been thinking Carwings is too optimistic ... are you sure you didn't charge elsewhere (like at the dealers).

During that 1/12 - 2/1 timeframe, I practiced "Charger Monogomy" at home except for the 15-20 minutes at Malcolm's to show Jim the detailer how the charger worked...

Randy said:

... "Charger Monogomy" ...

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:lol:

Your LEAF must be pleased with you :lol:

Randy said:

During that 1/12 - 2/1 timeframe, I practiced "Charger Monogomy" at home except for the 15-20 minutes at Malcolm's to show Jim the detailer how the charger worked...

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So u think u are gettting near 100% charger effiiency?

I am amazed at your stats. Granted I have driven farther but I have used more than double the amount of power in less time

Randy said:

It is from 1/12 through 2/1. I used 83 kWh, and it was ALL in the Super off-peak timeframe (midnight to 5am). Even though I know I did all of my charging during that timeframe, I was expecting some Clipper Creek vampire watts during the other periods, but they showed zero.

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Very nice numbers! You will be getting a Blink, right? Will be interesting to see how the vampire draw on the Blink compares. I suspect that many will want to go back to the CC if they find that the Blink is like a vampire!

BTW - what's your driving like to get 3.88 mi / kWh?

Randy said:

During that 1/12 - 2/1 timeframe, I practiced "Charger Monogomy" at home except for the 15-20 minutes at Malcolm's to show Jim the detailer how the charger worked...

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"I've been faithful with you except for that one time ..." :lol:

I've to still wonder how this fits with
- optimistic miles/kwh numbers carwings seems to be showing
- wall-to-wheels instead of battery-to-wheels

DaveinOlyWA said:

Randy said:

So u think u are gettting near 100% charger effiiency?

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Charger efficiency is nowhere near 100% if there's any validity at all to the Carwings measurements. There are some misconceptions at work here.

The "consumption" figure in the downloaded spreadsheet version of carwings is the traction motor consumption. It does not count regen (or accessories). It's coincidence that it matches the electric meter value. You can see this by looking at the Carwings "energy economy" in the same spreadsheet - it's way higher than the actual wall to wheels measurement. The accessory value is not even show in the download, but it is reflected in the Total Used column (ie total used is consumption - regen + the not-shown accessory amount).

The reported figure of 3.88 miles per kWh wall to wheels is very good. Our car appeared to be getting about 3.2 early on...yesterday we got about 3.7 over 52 miles, in part I believe to improved technique. Carwings is overoptimistic for sure, or maybe a more accurate description is that it does not take into account charging or regen inefficiency. Dave is charging at L1 I believe, and he's getting somewhat lower wall to wheels (relative to me, Randy or Jimmy) - I think there's evidence that L1 is somewhat less efficient than L2 - of course weather/terrain etc. could factor in as well.

If we believe the net consumption figures from Carwings, then charging at L2 could be construed as less than 70% efficient. For example, according to Carwings we supposedly 'Used' 8.8 total kWh yesterday to go 51 miles, or 5.8 kWh per mile. "Consumption" (carwings spreadsheet) was 13.6. The 8.8 is that consumption (traction motor) - regen + accessories. To recharge after that drive took 3.75 hours @ 3.77kW (Clipper Creek) or 14.13 kWh. Odometer actually said 52 miles, so I'm calling that 3.7 wall to wheels.

Now, my 70% assertion is simply 8.8 (the car's net claim) over 14.13. I don't think it's _quite_ that simple though, because we actually were down 7 bars, which has got to be more than 8.8kWh. So the 8.8 is misleading if not simply wrong. Inefficiencies during regen could share some of the burden with charging.

Anyway, my main point is that the consumption figure in the carwings spreadsheet is not directly related to the amount of electricity pulled through the utility meter, even though it looks close.

It is interesting that the car's own internal miles per kWh generally falls somewhere in between Carwings and measured wall to wheels. Maybe extrapolating from that figure would be a fairer measure of charging efficiency. For example the car internally claimed ~4.2 m/kWh yesterday. That would be 12.4kWh. 12.4/14.13=88%. That I could believe.

As I explained earlier, it appears to me that there is an error in the CARWINGS use of the car's data, primarily concerning how Regen is included in the calculations.

Reports with "no" Regen might match better. Maybe someone can try that.

Reven should be ignored. It is not part of the efficiency calc. Efficincy should be charge from batt plus accesoories over charge from wall.
The whole regen thing is just noise or "free" energy. Sure it increases performance but still ultimately came from the wall or the battery

**edit**
ya what gary said..

I wish we had a good way to determine charge from the wall with 220 the only prob being the charge bled off when not plugged in which may be significant.

I don't have that issue with mine since I can unplug when not charging. It does read about 5 watts when plugged in on standby