I Beat EPA's 2.9 Miles/KWh : Report Your Monthly Mileage

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evnow

Well-known member
Joined
Apr 22, 2010
Messages
11,480
Location
Seattle, WA
Starting a new thread using Hill's idea.

Let us use this thread to document everyone's energy economy - and see how it compares with the EPA figures.

The main efficiency (or as they say, Energy Economy) figure from EPA is 34 KWh/100 miles or 2.9 miles/kwh. This kwh should be calculated at the wall - not carwings or what Leaf shows. This means, you should either have TED/kill-a-watt, separate meter or Blink to figure out the energy used by the car at the wall. You should also keep track of any charges done when not at home.

I suggest keeping track of and reporting the following figures. Copy the format below and replace with your actual numbers.

Code:
Month : MMM-2011
a. x,xxx Miles
b. xxx kWh (Wall - Blink/Seprate meter/TED etc)
c. x.x Miles/kWh (Wall)
d. x.x Miles/kWh (Leaf)
e. x.x Miles/kWh (CarWings)
f. $xx.x
g. x.x Cents/Mile
Where,

a = Total Miles (from Leaf odometer)
b = kWh used (from the wall)
c = Miles / kWh (a/b from above)
d = Leaf Miles / kWh (weighted average of what Leaf reports, if you reset the number every day)
e = CarWings Miles / kWh
f = $ spent on Electricity for the car
g = Cents / Mile (f/a from above)

Here is my example for March.

Code:
Month : March-2011
a. 565 Miles
b. 177 kWh (Wall - Blink)
c. 3.2 Miles/kWh (Wall)
d. 4.1 Miles/kWh (Leaf)
e. 4.9 Miles/kWh (CarWings)
f. $19.5
g. 3.4 Cents/Mile
 
ok i bite. stats for March

a. 1118.1
b. 337
c. 3.3
d 4.45
e. 5.7
f. $35.29
g. 3.1

u can toss carwings out the window. i apparently forgot to accept the ok screen or something although i cant find but a single day where the mileage is off by any significant amount and that was 5.2 miles off on a 24 mile day. but everyday was inaccurate and the inaccuracies ranged from .2 for short days up to 2.2 miles on longer mileage days (50+ miles)... either way, Carwings listed me as doing 954 miles. that is a huge discrepancy

on the cost.... last time i filled Prius 8 days ago, it cost $37.60 to fill up for a 450 mile tank....
 
Here' my data since LEAF delivery (1/13/2011).
a. 1796 Miles
b. 529 KWh (Wall)
c. 3.4 Miles / KWh (Wall)
d. 4.2 Miles / KWh (Leaf)
e. 5.8 Miles / KWh (CarWings)
f. $44.77
g. 2.5 Cents / Mile
 
So how are you folks coming up with cost of electricity? I can't think of any way to do that unless:
  • You never charge away from home, and
  • You don't generate your own electricity (solar or wind), and
  • You have a completely flat electric rate - no tiers and no bulk rate reduction and no time of day or day of week variation.

My guess is that leaves out at least 90% of all LEAF owners at present.

If you do meet those conditions you can calculate the cost as a simple multiplication from item (b). The only real significance of the number is, then, that electric rates vary widely. This is largely out of our personal control and not useful to anyone with a different rate or rate structure.

That said, it would be interesting to see items (a) through (e) on a spreadsheet.
 
planet4ever said:
So how are you folks coming up with cost of electricity? I can't think of any way to do that unless:
If you can figure out how much electricity you used and how much the electric bill was - calculating the cost of electricity isn't a problem. Either use marginal cost to get the cost of electricity or just get the average cents/kwh from the total bill and use that.
 
If you are in a steeply tiered rate structure (PG&E), marginal rates can be very different from average, as much as 4 or 5 to 1 at worst. Average rates are not really relevant in this case.
 
DeaneG said:
If you are in a steeply tiered rate structure (PG&E), marginal rates can be very different from average, as much as 4 or 5 to 1 at worst. Average rates are not really relevant in this case.
That is a subjective discussion - depends on what you think is the marginal use of electricity at home. But yes, the rates can be quite different.

BTW, I'm using merginal rate - which is about 11 cents compared to the base rate of 8 cents.
 
evnow said:
Getting back to your original topic - let us see what what "beating the epa" in Leaf means.

The main efficiency (or as they say energy economy) figure from epa is 34 kwh/100 miles. This turns to 2.9 miles/kwh. This kwh should be calculated at the wall - not carwings or what the car shows. This means, you should either have TED/kill-a-watt, separate meter or Blink to figure out the energy used by the car at the waleport.
ok Evnow, so your personal calc's show 2.9 ... I'm curious - how much does that differ from what your dash displays.
 
hill said:
ok Evnow, so your personal calc's show 2.9 ... I'm curious - how much does that differ from what your dash displays.
Hmmm ... 34kwh/100 miles implies 100 miles/34kwh or 2.9miles/kwh. This is the EPA rating.

So, anything above this 2.9m/kwh is better than EPA i.e. you are beating EPA's mileage.
 
Here's mine. I'm not reporting CARWINGS data, since my uploads have been so intermittent.

Code:
Month : March-2011
a. 650 Miles
b. 208 KWh (Wall)
c. 3.1 Miles/KWh (Wall)
d. 3.5 Miles/KWh (Leaf)
e. --- Miles/KWh (CarWings)
f. $25.00 ($0.12/KWh -- PSE + 100% renewables upcharge)
g. 3.8 Cents/Mile
 
How to figure cost for me is easy. I can monitor exact amount of power I use.
As far as determining costs. There are two ways and each comes out nearly identical so I took the most expensive way.
PSE uses tiered rates based on usage. I only access the lower two. What I do is divide the total kwh I use by total of bill.

The alteurnative method is to divide by only the power charged at the higher rate plu the taxes involved. This ignores the monthly service fees.
 
I think the power cost calculation should be a comparison of what your electricity bill would be if you never bought the car, vs. with the car and your current driving habits.

It's easy enough if you have a flat rate (use average cost from your bill). It's only a little harder if you have a tiered bill (use the marginal rate which probably depends on the month or season).

Things get cloudier if you switch to a TOU rate (need to compare your total TOU bill with EV consumption, vs. what your bill would have been without TOU rates and the EV).

And then if you have solar ? I added solar only because the EV would have been untenable without it, I'd have been better off buying gas for a 328i. Clearly it is reasonable to amortize some portion of the PV system cost into my EV charging cost, but not clear how much.

So, with new solar PV and a deeply funky TOU rate structure, I can't tell you how much my Leaf costs per mile within a factor of two or so. Like driving it though.
 
planet4ever said:
So how are you folks coming up with cost of electricity? I can't think of any way to do that unless:
  • You never charge away from home, and
  • You don't generate your own electricity (solar or wind), and
  • You have a completely flat electric rate - no tiers and no bulk rate reduction and no time of day or day of week variation.
There's no public charging infrastructure, so very few owners can charge away from home. I don't have solar. But I do have a separate meter/billing for my EVSE, so it's simple to know exactly what my costs are.
 
ENIAC said:
But I do have a separate meter/billing for my EVSE, so it's simple to know exactly what my costs are.
That's lucky! Was there an installation cost to be amortized for the second meter ?
 
i have the opportunity to charge away from home but have chosen not to in order to get a better line on my charging efficiency. so i do know that what it costs me to drive and how far each kwh takes me so i am good.

i only really want to know why Carwings says what it says and why my car says what it says.

so its either my car also overestimates the performance like carwings and i am charging at 85+% or its pretty accurate and i am charging at 73%.

unfortunately, monitoring charge at anything other than 120 is not all that easy. so it goes.

but in the long run, it all boils down to what is coming out of my pocket and with a relatively stable ratio of wall/car, i am work with that
 
DeaneG said:
ENIAC said:
But I do have a separate meter/billing for my EVSE, so it's simple to know exactly what my costs are.
That's lucky! Was there an installation cost to be amortized for the second meter ?
It really wasn't luck. I signed up for the EV Project as well as the SDG&E EV ToU study. So pulling the 240V 40amp circuit, second meter, and Blink EVSE were provided free of charge.
 
Maybe also useful to state for item (b) how the wall AC power was measured - Blink, dedicated (second) utility meter, Kill-a-watt, etc.
 
For the data here so far the typical Leaf DC/Wall AC efficiency figure seems to run about 0.8, a little lower for Dave (120v charging effect?). Preheating/cooling will have a noticeable effect on this figure.
 
planet4ever said:
So how are you folks coming up with cost of electricity? I can't think of any way to do that unless:
  • You never charge away from home, and
  • You don't generate your own electricity (solar or wind), and
  • You have a completely flat electric rate - no tiers and no bulk rate reduction and no time of day or day of week variation.
. . . . . . . . . . . . . . . . . . . . . snip

I think you're (imo) missing all the FUN of this . . . getting bogged down with cost of electricity ... whether on a tier, or TOU ... the FUN is translating the difference of what a gallon of gas would get you ... ie 34kWh ... then stating what your EV range is as an equivalent. Meah . . . maybe that's just me.
:)
 
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