Best way to track energy usage/cost?

I just don't reset the trip counters and use the kW number plus a fudge factor for charging losses. Some people monitor the input power from the wall. Because automotive grade sensor apparatus accuracy is probably around 5% (due to tire RPM variance, sampling frequency, rounding errors, etc.). So unless you install special laboratory grade equipment, there's no need to be all that picky about the number.

You will find yourself charging at so many different locations. Some free, some not. You could set the units on the "Settings" tab to "energy" when you charge. That tab will display kilowatt hours added to your car rather than miles. (It also displays the share of charge in the battery as a percentage.) Then you will need to record the number of kWh added to the car at each location with the appropriate cost. Some charging stations in the wild are free and others are not. This will get close enough, but still is not entirely precise due to the factors that jerry33 mentioned above.

Regardless, you will have to maintain a sheet to keep with you in the car to record your "fill ups."

jerry33 said:

I just don't reset the trip counters and use the kW number plus a fudge factor for charging losses. Some people monitor the input power from the wall. Because automotive grade sensor apparatus accuracy is probably around 5% (due to tire RPM variance, sampling frequency, rounding errors, etc.). So unless you install special laboratory grade equipment, there's no need to be all that picky about the number.

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Curious how much fudge-factor loss can be assumed from wall to battery? 10%?

rjcbox said:

Curious how much fudge-factor loss can be assumed from wall to battery? 10%?

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you should be able to find the exact number on other threads. i remember this being analyzed before with ppl that have the circuit monitored with those TED devices. I want to say it was something like 92% efficient. cant remember exactly.

rjcbox said:

Curious how much fudge-factor loss can be assumed from wall to battery? 10%?

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10% to 15% depending. However, a few Supercharger trips makes up for it.

If you are only paying for electricity at home, I think a device like this would give you the actual amount of electricity you paid for:
Meter
I have heard charging is about 85% efficient so your 44KWh used cost more like $2.07 rather than $1.76

I had the same idea when I got my car but quickly realized it's very difficult. Superchargers are free, public chargers have all kinds of different prices and other fees so they can't easily be converted to cost per kWh. Home charging can be monitored with a $100 power meter but you still have to account for different rates depending on the time of day.

I do have a very good idea how much car used over it's lifetime as I never reset the trip meter. It shows me the total amount of power I used over the lifetime. I also know I pay 10 cents per kWh at home and Superchargers are free. I guess the number of miles from Supercharger trips vs daily driving, add a few $ for public charging here and there and that's it in terms of total cost.

Putting it in a simple way, I know I pay aprox $0.03 per mile for daily driving (charging at home) and I pay nothing going on road trips using Superchargers. That's accurate enough for me.

bjwModelS said:

I'd like to track my overall usage/cost of driving and was wondering if anyone has found a good way to slice the #'s.

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I posted this a while back and it looks like someone have an app for the Apple devices. unfortunately I don't use apple, I am still waiting for for Tesla to add a way that the car can tell how much juice goes into the car in total. My take is that if we want to know the real cost we must include the energy used not only to drive but to completely power the car then calculate the cost per mile, otherwise anything not considering the vampire will make the cost unreal.


Keep track of energy cost per mile

bjwModelS said:

I'd like to track my overall usage/cost of driving and was wondering if anyone has found a good way to slice the #'s.

For example, my first 221 miles showed 44kWh used. At $.04/kWh = $1.76

But then I drove 179 miles, with the car showing 52.7 kWh used. I stopped at a supercharger and got 132 miles back so I'd like to show that at $0.00 but I'm not sure what to do with the other 47 miles from the day, or how many kWh that represents. It was all highway driving, so should I just average it out and say 1 kWh every 3.4 miles, so 132/3.4 = 38.8 kWh "free" and then 13.9 kWh "paid" once I got back home and charged up?

Thoughts?

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You pay $0.04/kWh and you want to track usage? Seriously? SoCal Edison charges tiered rates of $0.16 to 0.31 and is announcing a 10% increase on the lower tiers.

I've noticed that many people (myself included) simply don't reset trip meter B. That gives you an idea of consumption through the life of the car, but obviously doesn't differentiate between the sources. I've also wondered if there is a screen somewhere back in the settings that gives the lifetime numbers?

Remembering that I was using fuelly.com to track my ICE vehicle fuel consumption, I just reached out to see if they would add kWh as an option to Litres and Gallons... a logical next step for the site and one that really follows the calculations already being done. Ideally, that site (or equivalent) would be accessible on the browser and data could be entered after each charge... although I don't see myself doing this each and every morning, so, maybe not that useful?

beeeerock said:

I've noticed that many people (myself included) simply don't reset trip meter B. That gives you an idea of consumption through the life of the car, but obviously doesn't differentiate between the sources. I've also wondered if there is a screen somewhere back in the settings that gives the lifetime numbers?

----- data could be entered after each charge... ----

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This is something the car itself could do, perhaps send an email with the data to a programmable email address with the data for that last charge.
It should contain the car total miles, the gps location and the total amount of the juice gone into the car, perhaps the length of time the car was plugged in.
I can volunteer to accept such email, process it and make the data available to the user in a private site.

spc said:

This is something the car itself could do, perhaps send an email with the data to a programmable email address with the data for that last charge.

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The Chevy Volt does this as I receive an email each month of monthly and total energy usage.

dhrivnak said:

The Chevy Volt does this as I receive an email each month of monthly and total energy usage.

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I got one of those and it is nice to know the telemetry. like the tire pressure, energy info and all the nice little things the volt puts on that email.
such an easy thing to do really Tesla.... I am surprised this is not standard feature already. not even the very important tire pressure data is available real time like the volt does.

just as important to me to know the real amount of energy that has gone into the car the last time it was plugged in, is the amount of energy used by the climate system in real time so we can adjust our driving and comfort to be able to arrive at our destination and the tire pressure and temp just like the energy it is using to move. a bit more precise then a needle on a display showing 10, 20 ,30....



Fuel Economy:85 mpg
Electric Consumption: -- kW-hr/100 miles
Electric Miles:398
Gas Miles:265
Percentage on Electric:60 %
Estimated Gallons of Fuel Saved:21 gal
Estimated CO2 Avoided:408 lbs

then it also gives you several links like:
Energy efficiency History
Driving History
charging history

spc said:

This is something the car itself could do, perhaps send an email with the data to a programmable email address with the data for that last charge.
It should contain the car total miles, the gps location and the total amount of the juice gone into the car, perhaps the length of time the car was plugged in.
I can volunteer to accept such email, process it and make the data available to the user in a private site.

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This would be interesting... as I was sending a feature request to Fuelly, I was wondering whether I'd be diligent about adding daily charge information to my personal account each and every day. The answer... "Not blinkin' likely!"... especially since the information is gone as soon as you disconnect the charge cable.

I might, however, add the information before resetting Trip A. But having the data available via an email, or software like Visible Tesla, would be nice. It could simply be XML data that we accept and add to our own database.

Hardly mission-critical stuff, but interesting data to keep track of. Odds are, Tesla already is...