App Charge Stats don't agree with my electric meter

[Erland Lukanen]

Why does my electric meter show about 50% more kWhs used than my Tesla App Charge Stats?

 

[Sophias_dad]

Because your electric meter also supplies your house.

 

[Erland Lukanen]

Because your electric meter also supplies your house.

This is an electric meter that only supplies the Tesla charger. There is nothing else connected to that meter. That was required by our electric company to get off peak rates.

 

[RayK]

This is an electric meter that only supplies the Tesla charger. There is nothing else connected to that meter. That was required by our electric company to get off peak rates.

Is your meter/Tesla charger on a 240V supply, or is it only 120V? I ask since if you charge at the lower voltage, the power going to the car's computer and accessories (i.e., not going into your HV battery) is a much greater percentage than if you are using 240V. It's not going to be 50% but it is a fair amount that could account for some of the difference.

 

[jdcollins5]

It could be a loose connection in the electric meter. It may only be seeing 120V and not 240V.

 

[RayK]

I would think that the meter is really measuring amperage (current) running through the connection and calculating wattage by multiplying by the voltage that's assumed to be provided. If that's the case, and the meter is "seeing" 120V when it's really connected to 240V, then the meter would read half the power that's being consumed. OP has stated it's 50% more than expected when compared to the Tesla app. As I don't charge at home and have never paid any attention to what the app is keeping track of, I can't offer any knowledgeable guess as to what's going on.

I would also assume that all electric meters are normally tied into 240V but as I never worked as an power company employee I could be wrong.

 

[Sophias_dad]

A picture of the meter(at start and end of charging) and the charge rate(amps and volts) and the tesla app charge stats information would go a long way in solving this.

My first guess is misreading of the meter. They can be a little tricky since analog meters have each needle turning a different direction.

 

[ATPMSD]

If you charge at 120v you are only 80% efficient, at 240V you are between 90-95% efficient.

If you leave the car plugged in after you charge the car will continue to draw power. I believe this is about 1 kWh per day (7 kWh per day if you leave Sentry on) and this will not show up in the charge stats since you are not charging the HV battery. Whether or not this is true (I am not 100% sure) here is something you can try to determine if there is something to look into:

1. Read the meter and start charging the car
2. Immediately after charing has completed read the meter again. A 5-10% difference should be expected if charging at 240V and about 20% if charging at 120v.

 

[mongo]

I would think that the meter is really measuring amperage (current) running through the connection and calculating wattage by multiplying by the voltage that's assumed to be provided. If that's the case, and the meter is "seeing" 120V when it's really connected to 240V, then the meter would read half the power that's being consumed. OP has stated it's 50% more than expected when compared to the Tesla app. As I don't charge at home and have never paid any attention to what the app is keeping track of, I can't offer any knowledgeable guess as to what's going on.

I would also assume that all electric meters are normally tied into 240V but as I never worked as an power company employee I could be wrong.

Meters sample actual voltage along with current.
How Electric Meters Work and What Electric Meters Do

 

[UncleCreepy]

"Something is wrong. Why?" Is kinda hard to analyze without further information.
What kind of charging equipment is being used? What is it connected to?

The only thing I can tell OP is that the display in the car shows how much energy ended up in the battery while the power meter shows the entire energy consumed. While the car is awake, it consumes about 250 W just because it's awake. If you charge at 120 V/8 Amps you'll draw exactly those 8 Amps from the grid, but again, from the 960 W drawn from the grid only 710 W are used to charge the battery (all numbers are approximate).
That doesn't explain the difference you're seeing, but again, give us more details to work with and everybody here will be happy to help.

 

[AAKEE]

Why does my electric meter show about 50% more kWhs used than my Tesla App Charge Stats?

What charging power do you charge with?

The car is awake during charging, which means for a charge with low power there will be more energy lost.
If charging outside at close to freezing temps or below, the battery heating can be needed. This causes loss of power as well, specially at low charging power.
I do a lot of logging, and also checked a lot before a drive this weekend:
Charged to 100%. (from 30%):

The stand alone electrical meter (mounted directly before the WC) said: 57.12 kWh used.
The display on the car said 54kWh added.
Teslalogger that logs SMT data said 53.55 kWh added.
The difference in nominal remaining (via SMT, canbus data from the BMS) said 52.2kWh more energy.

Thats a 8.6% loss from the electric net to usefull enedgy in the battery. I use the Wall connector, three phase 230V 16A, so 11kW.

 

[Erland Lukanen]

Thanks for the inputs. Here is some more information.

I am using a Tesla wall charger that was installed last fall. It is supplied by a 240 volt 60 amp circuit. The Tesla charger states it output is 48 amps and the my app states that it charges at an 11kWh rate, or about 51 miles per hour of charging. The charger is in an unheated garage in Minnesota so I waited until warmer weather to see if preheating the car before going anywhere was what was using the extra power. The last meter reading from my power company was from about mid April to mid May, but the ratio of metered usage to the Charge Stat information on my phone App didn't change. I will continue to check month by month as long as I own the car (2023 M3 LR). My charging starts after midnight when off peak rates start and the car is typically between 60 to 80% charged and I charge to 90%. As for the 240 volt vs 120 volt comment, I suspect the Tesla Wall Charger would not work if one of the 120 volt sides were disconnected and the Tesla App on my phone would not. The electric meter installed Dakota Electric is a digital meter capable of measuring the amount of electricity used during three separate time periods of standard rate in the morning, peak rate in the late afternoon to early evening, and off peak rate from late evening to the next morning. I charge during the off peak time, but pre-heat the car during standard or peak times, depending on when I leave the house. (I am retired so no scheduled times.)

 

[ATPMSD]

May I suggest you break this down into bit size pieces to find the issue. I suggest you do as I suggested in post #8 and see what happens. But make sure pre-conditions is turned off, as power used to pre-condition is not included in the charging stats.

 

[Stew-2]

Some utilities use an estimated usage for some of the meter readings without using the actual kWh’s used and then adjust at the next real meter reading either up or down compared to their guess. Could that be what’s happening?

Edit: That would be if you were going off the billing statement rather than the meter itself.