Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Tesla’s Supercharging Math

cruzinhk

Member
Sep 9, 2019
20
-9
South San Francisco, CA
Does anyone has the same experience that Tesla always overcharges the supercharging fee?

For example, my car’s reading says 48.2 kWh is used since last charge so I thought it would cost me 48.2 X $0.28 (that’s the rate for this particular supercharger at Daly City CA) = $13.50 to charge up to the same level (90%).

It ended up $16.50 for the session. I noticed it every single time, just the matter of how much higher they overcharge. Tesla is disgusting.
 

ajdelange

Active Member
Dec 10, 2018
1,077
541
Virginia/Quebec
That's a 22% discrepancy. When super charging there is no loss from conversion from A/C to DC and the portion of the charge energy that goes to warm the internal resistance of the battery is more like 6%.
 

ewoodrick

Well-Known Member
Apr 13, 2018
5,285
3,735
Buford, GA
There's no loss converting from AC to DC? Then why is there so much heat coming from the inverter behind the wall? There definitely is loss.
And many of the car's numbers aren't as precise as you may think.

But since Tesla is definitely out to overcharge you, every thing I'm saying is probably moot
 

ajdelange

Active Member
Dec 10, 2018
1,077
541
Virginia/Quebec
There's no loss converting from AC to DC? Then why is there so much heat coming from the inverter behind the wall? There definitely is loss.
Well of course there is but you are billed by the volts and amperes delivered to the car - not the VA delivered to the station transformer.


And many of the car's numbers aren't as precise as you may think.
Sorry, can't find the place in my post where I expressed an opinion as to the accuracy of the car's numbers.

But since Tesla is definitely out to overcharge you, every thing I'm saying is probably moot
If you think that then you probably do think they are charging you for excitation VARs too. The question then becomes how do they allocate those to the individual cars at the station.
 

Krazaak

Member
Jul 30, 2017
909
1,004
Charlotte, NC
It tells you how many kWh went into the car during charging, that's what you're billed for. I don't believe power used while the car is parked, for cabin overheat or sentry mode is factored into the kWh consumed in the trip meter.
 

jimbo69ny

Member
May 12, 2018
403
173
Ithaca NY
I’ve been wondering about this a lot too. I have been doing a lot of testing but unfortunately I can’t really talk about it. I think Tesla collects a lot of data from multiple different points. The display in the car and the data that TeslaFi obtains is based on data from the battery BMS. NOT from the supercharger or any other point. So the display is showing actual power going into the power after losses.
 

dethman

Member
Apr 19, 2018
891
896
socal
car's reading of 'X kwh used since last charged' doesn't account for a lot of battery usage, such as when the car is parked and using sentry mode, when it's stopped and using the A/C, any preheating/precooling, and general crap tesla battery loss when idle.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top