Miles per kWh

[EngineerMom]

FWIW, this morning my 60 reported that it went 124.0 miles on 40.5 kWh since last charge. My kWh meter says it used 41.4 kWh from when I plugged it in at 10pm until I unplugged it this morning at 10am. I charged it on 240v, at 23 amps (to stretch it out overnight). (4.2 software)

That looks like 97.8% charging efficiency to me.

TXjak, was this from a whole-home electric utility meter? Especially when you consider that you would also need to subtract the baseline energy usage of your home during that 10 hours in order to know how much of the 41.4 kWh actually went into the car, that percentage feels too high. Vampire loads, refrigerators cycling, etc. can really add up, and it seems like once you accounted for baseline draw of other loads in the house, the calculated efficiency might even be over 100%. And then I'd come plug in at your house.

That said, your amperage was quite different from mine, and now my interest is really peaked. I have a minute by minute energy monitoring system so it's really easy to pick out the actual home baseline on any given night. I'll see if I can do some other experiments in the next couple weeks to look at the effects of 120/240V, temperature and charging amperage. Fun!

 

[TXjak]

TXjak, was this from a whole-home electric utility meter? Especially when you consider that you would also need to subtract the baseline energy usage of your home during that 10 hours in order to know how much of the 41.4 kWh actually went into the car, that percentage feels too high. Vampire loads, refrigerators cycling, etc. can really add up, and it seems like once you accounted for baseline draw of other loads in the house, the calculated efficiency might even be over 100%. And then I'd come plug in at your house.

That said, your amperage was quite different from mine, and now my interest is really peaked. I have a minute by minute energy monitoring system so it's really easy to pick out the actual home baseline on any given night. I'll see if I can do some other experiments in the next couple weeks to look at the effects of 120/240V, temperature and charging amperage. Fun!

No, I have a separate kWh meter in the garage feeding the 14-50 outlet for the car. One should probably not read too much into this, since it is only the first reading. Once I have more data I will be more confident with the results.

 

[smorgasbord]

ENERGY USE IN WH/MILE FOR THE FIRST 2,000 MILES

Here below is my energy use for the first 2,000 miles of driving. Below, I'll estimate the total cost based on my cost of kWh/mile, and I'll be happy to add what I actually paid when the bill comes, as the car is on its own meter.

View attachment 15293

About 800kWh to go 2,000 miles.

If I'm understanding this, then that's 800kWh out of the battery to go 2,000 miles. How do we calculate the power out of the wall?

For instance, the EPA sticker has a 380Wh/mile rating for Model S coming out of the wall. However, their 265 mile range on 81.5kWh of battery yields about 308Wh/mile from the battery. That ratio, 380/308=1.23, represents charging losses. That seems really high. So, if you used 800kWh out of the battery to go 2K miles, then you really used 984kWh out of the wall to go 2K miles. That's 492Wh/mile, or just over 2 miles/kWh.

Do we understand these charging losses? Even worse, with Model S's current firmware, some people are estimating 3kWh/24hrs of vampire drain and 2kWh/night of battery temperature management if the ambient air is 40degF. That's 5kWh/day of losses from the battery, which is over 6.2kWh/day of wasted energy from the wall. That's a lot of waste. Comments?

 

[mknox]

That's a lot of waste. Comments?

I share your concerns. I've compared this to an ICE with a small leak in its gas tank. I'm expecting my Model S in a couple of weeks, and will be charging at home from an outlet I intend to meter independently (I have a TED power monitor and will be adding a separate set of CTs and MTU to that circuit). The problem is, I expect to be charging at other locations that I will not be able to independently meter (at work, public stations and so forth) and these will likely be free of cost. I hope to be able to more than offset these losses with the free power I get elsewhere, and my calculations will be based on how far I drive against how many kWhs (and $) actually comes out of my pocket. I should come out way ahead. I have an 80 mile round trip commute, but if I can charge at work, I'll only pay for +/- 40 miles of use.

 

[shokunin]

Do we understand these charging losses? Even worse, with Model S's current firmware, some people are estimating 3kWh/24hrs of vampire drain and 2kWh/night of battery temperature management if the ambient air is 40degF. That's 5kWh/day of losses from the battery, which is over 6.2kWh/day of wasted energy from the wall. That's a lot of waste. Comments?

It is a lot of waste and it is noticeable. Part of me wishes I stayed with 4.1 with Sleep. I didn't have any issues with sleep and did not mind the LCD's taking a few seconds to warm up. The vampire losses are noticeable when charging as you'll see a visible delta between the KW used in the trip meter versus what KW was put back into the battery during charging (if you set your display to show +KW instead of +miles).

So much for being green. 6.2KW is more than 25% of my daily household electrical use.

 

[Iz]

I've noticed vampire loses as well. In a 36-hour period some miles were lost at temperatures in the mid 20's.

 

[Cliff Hannel]

Actual electricity usage is significantly more than what is reported by trip meter in car. From my experience (P85):
* trip meter seems to only measure usage while moving and under-reports actual battery drain
* charging efficiency, while maxing out at 92%, is more typically 80-85%
* parked consumption seems to run about 160 watts (in mild weather)...roughly .5 mph
Given all this, I put together something to calculate expected energy usage/cost that you can find at EV Calculations - here is a snapshot:

 

[teslasguy]

Wow! This chart amazingly nails my real world mileage and electricity usage/costs for the first two months of ownership.
I'm averaging around 1500 miles per month and my electricity bill has risen about $108 per month with kwh rate of .155

 

[Tesla 940]

My experience is only with the Roadster so there may be differences. It is my understanding that the Roadster accurately reports the actual Kwh from the wall. To determine AC/DC conversion loss all I've had to do is record the beginning Ideal Miles and the ending Ideal Miles (usually several hours after charging ended and the Ideal Miles has decreased due to battery balancing) and do some simple math. When I noticed a 20% - 25% loss I asked my PHD Electrical Engineering friend if that made sense. His response was "sounds about right". I suspect the Tesla 9% efficiency claim is about as meaningful as "150 miles in 30 minutes".

 

[Cliff Hannel]

the chart in the post is a little low since it does not include "parasitic" loads while not driving. Since then I've updated at EV Calculations (you can download spreadsheet and put in your actual rates/miles/etc)

 

[ModelS1079]

Gotta love that Seeking Alpha used our posts to back up range claims (Is The Tesla Model S Green? - Seeking Alpha).

Sadly, Nathan Weiss used only my mid-winter numbers (390's/kWh), whereas I have averaged much better since both the weather warmed and since I learned to drive more effectively with regen and acceleration, and therefore more efficiently. I do not drive slowly, but with intelligent regen use and smart acceleration (never to the exclusion of just GUNNING IT once in a while), I am now getting near or over 300 miles/charge at best (averaged 274 wh/mile on 110 miles driving yesterday , and am getting the exact rated range at the worst (240 standard, 265 max range charge).

Will report again at 10,000 miles (that's about two-three weeks away). Will post pic of the trip numbers when I get to a home computer.

 

[Jeff Miller]

Gotta love that Seeking Alpha used our posts to back up range claims (Is The Tesla Model S Green? - Seeking Alpha).

Sadly, Nathan Weiss used only my mid-winter numbers (390's/kWh), whereas I have averaged much better since both the weather warmed and since I learned to drive more effectively with regen and acceleration, and therefore more efficiently. I do not drive slowly, but with intelligent regen use and smart acceleration (never to the exclusion of just GUNNING IT once in a while), I am now getting near or over 300 miles/charge at best (averaged 274 wh/mile on 110 miles driving yesterday , and am getting the exact rated range at the worst (240 standard, 265 max range charge).

Will report again at 10,000 miles (that's about two-three weeks away). Will post pic of the trip numbers when I get to a home computer.

We should definitely update all our totals on the Lifetime-Average-Wh-mi thread.

Lifetime Average Wh/mi - Page 13

I'll tally up all the numbers.

 

[EarlyAdopter]

Gotta love that Seeking Alpha used our posts to back up range claims (Is The Tesla Model S Green? - Seeking Alpha).

Sadly, Nathan Weiss used only my mid-winter numbers (390's/kWh), whereas I have averaged much better since both the weather warmed and since I learned to drive more effectively with regen and acceleration, and therefore more efficiently. I do not drive slowly, but with intelligent regen use and smart acceleration (never to the exclusion of just GUNNING IT once in a while), I am now getting near or over 300 miles/charge at best (averaged 274 wh/mile on 110 miles driving yesterday , and am getting the exact rated range at the worst (240 standard, 265 max range charge).

Will report again at 10,000 miles (that's about two-three weeks away). Will post pic of the trip numbers when I get to a home computer.

Oh god, they used data from one my posts in their short seller hatchet job. Ugh, I feel dirty... violated... used... and also rather surreal.

 

[FalconNinetyD]

Just another desperate person who shorted TSLA...

 

[neroden]

If Nathan Weiss or any other Tesla-basher out there wants to use my mileage numbers (which aren't that great) to back up their bogus claims that the Model S emits CO2, they'd better point out:
(1) I buy 100% renewable electricity, so actually I'm not causing any additional CO2 emissions at all
(2) mileage for gasoline cars on the (steep, hilly) routes I drive is quite terrible -- much worse than goverment-rated mileage. This is due to the massive amounts of energy they waste while going downhill. Model S uses no electricity, and in fact charges, while going downhill. Mr. Weiss's "Honda Civic" will not get anywhere near 27.4 mpg on my local hills.