Model 3 showing wrong kWh consumption?

[borugee]

I charged my car to 80% after 41miles of driving, it is now at 52%. Since last charge kWh show 14kWh. I did 4 trips of about 10 miles each in winter to accumulate these 41miles. (Also preheated car 2 times for about 10 minutes each). My car LR-AWD charge to 300miles.

Here is my math to show some kWh has gone missing?

Battery size 75kWh (with some degradation real capacity should be around 72kWh).
100% = 72kWh
1% = .72kWh

80%-52% = 28% which translate to 28% * 0.72kWh = 20kWh Used.

However Display show 41miles / 14 kWh / 338 Wh/mil.

So I have a discrepency of 6kWh (20-14). (Don't know where this lost energy went.

Is that missing 6kWh used for heating? (I had mild winter, temperatures were between 40-55F)

My real efficiency is closer to 500Wh/mi (20kWh used in 41 miles = 487Wh/mi) as per my calculations. (What am I missing - Is this normal for Tesla cars during winter?, How tesla report Wh numbers are not accurate or they are not showing energy used for heating.).

I can charge my car back to 80% and see how much electricity it took to travel 42miles.

 

[jdcollins5]

The Trip Meter only shows kwh used while in gear. It does not show kWH use while in park. Preheating will not show up in Trip Meter.

 

[borugee]

The Trip Meter only shows kwh used while in gear. It does not show kWH use while in park. Preheating will not show up in Trip Meter.

That can explain..

You think it is reasonable to loose about 6kWh of energy for pre-heating? 6kWh is about 20miles of range. That is lot of energy for heating for 2 times & 10 minutes each.

 

[Magnets!]

That can explain..

You think it is reasonable to loose about 6kWh of energy for pre-heating? 6kWh is about 20miles of range. That is lot of energy for heating for 2 times & 10 minutes each.

Short trips are worse as the energy required to heat up the car is a lot. If you were to do a longer drive, the car would be warm and not nearly as much heat needed to keep it warm.

 

[dhrivnak]

I can reiterate that short trips and preheating definitely use significantly more power and the trip computer is only counting when the car is on.

 

[swaltner]

To give you an idea of the difference between kWh consumed at the outlet and kWh as reported by the trip meter, here are 19 months of records for me. Note that most of the kWh consumed at Superchargers are guesstimates, because I typically pay by the minute, not by the kWh. Some of this difference is the vampire drain, some is pre-conditioning the cabin in the summer/winter, and some is the energy lost during the AC to DC conversion and charging the battery. Also note that the Home Cost column is all over the place on a per-kWh rate due to me having solar panels at home that produce some/all of my electricity needs at home.

For example, in January of last year, the trip meter said I consumed 367 kWh, where in reality, I consumed 509 kWh charging the car at home. The electricity consumed was 38% higher than what the trip meter said was used. This discrepancy can happen when you pre-heat the car every time you get into it.

Edit: The Home kWh column comes from a dedicated MTU on the TED 5000 system I have at home. This tracks the voltage/amperage going to the EVSE at the main breaker panel and calculates a running total of the kWh used to recharge the batteries in the car.

 

[borugee]

@swaltner Thank you for the great info. To the completeness of this thread, I charged my car back to 80% and it took, 22kWh of energy.

So the story is,
From Utility company, 22kWh of electricy drove me 41 miles. Some of the energy may have wasted during charging and during pre-heating. (If I did not pre-heat, I assume, it should show up, in energy used to drive, as car and battery need to be haeted during driving anyway - wish tesla had a heat pump to heat which is considered much more efficient).

 

[AlanSubie4Life]

@swaltner Thank you for the great info. To the completeness of this thread, I charged my car back to 80% and it took, 22kWh of energy.

So the story is,
From Utility company, 22kWh of electricy drove me 41 miles. Some of the energy may have wasted during charging and during pre-heating. (If I did not pre-heat, I assume, it should show up, in energy used to drive, as car and battery need to be haeted during driving anyway - wish tesla had a heat pump to heat which is considered much more efficient).

If you use a 240V charging method, charging efficiency is 88-89%. This is very clear from the EPA data.

However, referenced to the charging screen, the apparent efficiency is closer to 93-94% (this is false; it is in error by 4.5%, the buffer size).

When referenced to the trip meter, you lose a couple % more.

So, 86% or so of the energy you put in from the wall will show up on the trip meter. (If you use 120V charging it’ll be closer to 65-70%)

If you are comparing trip meter to charging screen data (all DC numbers), you’ll see about 93.5% of the charging screen energy show up on the trip meter assuming none goes “missing”. (4.5% + ~2% loss)

However, all of the above neglects any vampire drain or losses you will have while parked (not counted, as mentioned above). For most users, the minimum loss is about 10%. For people who drive 20k+ miles a year might be as low as 5%.

So best case about 75-80% of your wall energy will show on the trip meter.

So, rough rule of thumb, multiply trip meter value by 1.25 to get the minimum wall energy. If you use Sentry or preheat, you may well need to use a larger scaling - 1.4 or 1.5 or more.

 

[AlanSubie4Life]

Battery size 75kWh (with some degradation real capacity should be around 72kWh).
100% = 72kWh
1% = .72kWh

Correcting this:

When new, battery is ~78-79kWh.
100% = 79kWh
0% = 0.045*79kWh = 3.6kWh (buffer)

After 7% degradation:
100% = 73.5kWh. (300 AWD rated miles)
0% = 0.045*73.5kWh = 3.3kWh (buffer)

So you used 0.28*70.2kWh = 19.6kWh

You see 13.86kWh used. So missing 5.7kWh which is totally reasonable for heat - heat plus AC at max is 9kW so if it is very cold that would be 40 minutes of heat (but there are other sources of loss too - your car loses about 1kWh a day just sitting there).

 

[jaguarrr]

I recently got a Model Y and noticed the same issue, that the Trip Meter showed a widely different value than what the car really consumed. Below are some numbers over the last 8 weeks:

I just think that it's at least misleading to show the values in Trip Meter only for some parts of what the car consumes and not all of them ...
I would love to have the total consumption as well, not just a number that Tesla prefers to show.