Questions on real electricity consumption

[KoenMertens]

Hello all,


I am hoping to gather some information about the real electricity consumption of an EV.

Advertised we see the number of kWh / 100 km. But is there any other electricity consumption we should take into account? I am thinking e.g. of the fact that the Tesla is best plugged in as much as possible, vampire drain, battery optimizations,...

Does anyone have any figures on this? What additional consumption should we take into account? Or is this negligible?

 

[Metralla]

Hello all,


I am hoping to gather some information about the real electricity consumption of an EV.

Advertised we see the number of kWh / 100 km. But is there any other electricity consumption we should take into account? I am thinking e.g. of the fact that the Tesla is best plugged in as much as possible, vampire drain, battery optimizations,...

Does anyone have any figures on this? What additional consumption should we take into account? Or is this negligible?

Negligible in my experience.3 years ownership, I can leave my car for days without using it or plugging in, very little change in state of charge.

 

[Watts_Up]

If you charge at home, install a Watmeter next to your charger,
and every time you charge your car make a note of:
- your current mileage, and also the car has a special display "mileage from last charging",
- power sent to the charger
- energy stored in the battery.

Then every month, compare the energy consumption for the mileage driven
and compare to the energy consumption indicated by the car.

The energy lost by the inverter when charging form AC to DC will be the major
additional consumption and cost, about 15% losses or 85% efficiency.

I would also recommend installing a 12V monitor so you can see how often
the DC/DC inverter is used to charge your battery. While not driving last year
because of Covid, I noticed a 1% discharge a week or 3 to 4% a month,
of the propulsion battery, mostly to charge the 12V battery every 2 or 3 days for 1 hour.

Having a 12V monitor is also a good way to check your 12V battery,
but if you have a 16V Lithium-Ion battery you don't have to worry about it.
Here is a good review of the 16V Li-Ion battery.

 

[zroger73]

I am hoping to gather some information about the real electricity consumption of an EV.

1. First, there is the consumption displayed in the vehicle. This is shown as energy/distance, such as Wh/mi (watt-hours per mile) and total energy in kWh for the current drive, since the last charge, and for each trip meter (A and B). This is the amount of energy used by the vehicle while driving. It does not account for the energy used while parked such as for Sentry Mode or HVAC use (Camp/Dog/Keep Modes, evaporator drying, Cabin Overheat Protection). There is no indication for the actual amount of energy used by the vehicle.
2. Second, there is the Total Charged indication under Charge Stats in the mobile app. This shows you how much energy went into the battery during charging. It does not account for charging losses in the on-board charger that occur during the conversion from AC to DC nor the energy required to run the computers, coolant pumps, fans, heat pump, etc.
3. Third, there is the amount of power shown in the Charge History for a Wall Connector in the mobile app. This shows you the total amount of energy delivered from the Wall Connector to the vehicle for the entire charging session. This number does not include losses between your electricity meter and the Wall Connector. If the Wall Connector is close to the meter using appropriate wiring, this loss will be minimal. If the Wall Connector is far away from the meter and the wiring is not upsized to account for the distance, the loss will be greater.
4. Fourth, there is the amount of energy metered by your electricity provider. This number divided by the distance traveled is the one that reflects your true cost, but unless you have a separate electricity meter for your Wall Connector, you won't know what this amount is.

1 makes the vehicle's efficiency appear better than it really is. I consider it to be misleading. I believe it should not exclude energy used while the vehicle is parked. It shouldn't matter whether the vehicle is using energy to propel the vehicle or condition the cabin. If you run the HVAC in an ICEV while parked, the engine is consuming gasoline - this use will be reflected in the vehicle's fuel economy calculations. Let's say your ICEV's trip computer is indicating an average of 28.0 MPG then you start the engine to run the A/C while parked. You'll see the MPG slowly drop every few minutes to 27.9 MPG, 27.8 MPG, 27.7 MPG, etc. If you park your Tesla and turn on the A/C, you won't see the energy/distance or total energy change when the vehicle is in park even though energy is being used.

2 is also pretty useless. This number will be higher than 1, but it still doesn't tell you the actual amount of energy used by the vehicle.

3 is the most accurate number for actual energy use that you'll find unless you have a seperate meter for EV charging.

4 is the only one that really matters, but most people won't be able to see this number.

So, the next question becomes: How much of a difference is there betweeen 1, 2, 3, and 4?

You can determine this by comparing your own numbers.

The answer depends on variables such as ambient temperature, charging rate, whether you use the HVAC while charging, the type of charging equipment being used, and how your charging equipment is installed.

When I divide the total distance I traveled by the amount of energy deliver to the vehicle by my Wall Connector, that number is about 20% higher than what the vehicle indicates.

When I charge at a public charging location that has a long run from the electricity meter to the receptacle for my Mobile Connector, the number is about 26% higher than what the vehicle indicates.

TL;DR - the actual amount of energy that you must purchase for your vehicle will be ~15-25% higher than what the vehicle itself indicates.

I had a similar discussion in December...

Why Wh/mi?

To me it seems counter intuitive to express efficiency in terms of a number that you want to minimize. The ICE equivalent is miles per gallon, so why not adopt the inverse of Wh/mi? As the capacity (energy) of our batteries is expressed in KwH, why not state efficiency figures in terms of...

teslamotorsclub.com

 

[fhteagle]

OpenEVSE says ~2200kWh, Tesla says ~1900kWh charged at home, so 17% discrepancy. I assume this includes charging inefficiency, preconditioning, and any inaccuracy in the OpenEVSEs ability to meter accurately.

For the last year, Tesla is reporting ~280Wh/mi in the app. Adjusting upwards by the discrepancy above, puts us at ~320Wh/mi including inefficiencies, preconditioning, etc. Cold mountain climate here so preconditioning is pretty significant.