Supercharger charging costs delivered or accepted?

[Falcon73]

I just watched an interesting video on State of Charge.

Tesla (EV) Charging Losses Explained

It got me thinking if Tesla charges by the amount the car battery accepts (the kWh on the screen) or by the kWh the pedestal puts out?

I will be checking next time I go to a Supercharger. Since the pedestals lack screens this becomes more interesting.

Anyone know? If it's what the battery accepts it would be cheaper than what it appears, at least compared to other networks with screens.

 

[Lasky]

The lost should be min with supercharger. Less than 5% since 240v home charging only lost 5%.

 

[Sophias_dad]

I just watched an interesting video on State of Charge.

Tesla (EV) Charging Losses Explained

It got me thinking if Tesla charges by the amount the car battery accepts (the kWh on the screen) or by the kWh the pedestal puts out?

I will be checking next time I go to a Supercharger. Since the pedestals lack screens this becomes more interesting.

Anyone know? If it's what the battery accepts it would be cheaper than what it appears, at least compared to other networks with screens.

It'll certainly be the amount the car accepts. Imagine the uproar when one plugs into a 250kw charger and gets charged as if its taking that much for the entire period its charging. It could be double, triple, even ten times the actual amount of energy delivered. The ten times would be a rather ludicrous charging session, plugging in at 90% or more.

People certainly would have noticed by now.


I assume you are not asking about the ~5% parasitic losses between the charger and the battery. You'd have to pay for that.

 

[jcanoe]

The charging rate (kW) will vary throughout the Supercharging session. The only thing that matters is the total kWh for the session. Charging overhead from heating or cooling the battery while Supercharging, any heat losses within the charging cables and battery mean that it takes more than 20kWh to add 20kWH to the Tesla's battery. Perhaps 5% more. In this example an additional ~1kWh would be consumed that never makes it into the battery.

If you were pumping gas, pumped 20 gallons, you expect to pay for 20 gallons. If you spill some gas as you take the fuel nozzle out of the vehicle and an ounce of gas spills on the ground, well you paid for that gas too but it never made it into your fuel tank.

 

[watsongrg]

Tesla can’t charge by the KWh because they are not a utility. So they charge a variable /min. rate throughout the charging session. That keeps it equitable since the KWh delivery is so hugely variable throughout the charge session.
Quite genius actually. Pull up charge history in app and it shows the variable rate.

Traditional public chargers were a set /min rate, and that stinks for cars that don’t charge fast. It would be very expensive to charge a (slow) PHEV vs. a ( fast)EV. I never used a public charger for that reason in the Volt or Plugin Prius

 

[Falcon73]

Tesla can’t charge by the KWh because they are not a utility. So they charge a variable /min. rate throughout the charging session. That keeps it equitable since the KWh delivery is so hugely variable throughout the charge session.
Quite genius actually. Pull up charge history in app and it shows the variable rate.

Traditional public chargers were a set /min rate, and that stinks for cars that don’t charge fast. It would be very expensive to charge a (slow) PHEV vs. a ( fast)EV. I never used a public charger for that reason in the Volt or Plugin Prius

This must vary by state/region as Tesla charges me $0.48/kWh here, as least during the times I've charged. There are lower costs off-peak, but sleep is good.

My question is whether they charge on Gross or Net kWh delivered. i.e. with the loss or w/o the ~5-10% loss. If it IS with the loss, it would seem easy to calculate the loss just by looking at what we are charged vs. how many kWh the car says it received.

Imagine if gas cars spilled ~10% of their gas when being filled. The station would certainly charge the Gross gas dispensed out of the pump. They don't care how much gas you spilled.

 

[rob1987]

The lost should be min with supercharger. Less than 5% since 240v home charging only lost 5%.

I’d think the opposite is true. Direct DC fast charging generates a lot of heat which is energy that is delivered not accepted.

This must vary by state/region as Tesla charges me $0.48/kWh here, as least during the times I've charged. There are lower costs off-peak, but sleep is good.

It definitely varies by region. Tesla even implies this is the case on their website where they state, “Whenever possible, owners are billed per kWh (kilowatt-hour); in other areas, owners are billed per minute.”

 

[jcanoe]

I don't believe Tesla has every claimed that Supercharging is the least expensive way to charge (unless your Tesla vehicle qualifies for free Supercharging.) Supercharging charging costs are pretty much on par with the cost of gas. When you are hundreds of miles from home, want to charge quickly what else can you do?

 

[sleepydoc]

This must vary by state/region as Tesla charges me $0.48/kWh here, as least during the times I've charged. There are lower costs off-peak, but sleep is good.

My question is whether they charge on Gross or Net kWh delivered. i.e. with the loss or w/o the ~5-10% loss. If it IS with the loss, it would seem easy to calculate the loss just by looking at what we are charged vs. how many kWh the car says it received.

Imagine if gas cars spilled ~10% of their gas when being filled. The station would certainly charge the Gross gas dispensed out of the pump. They don't care how much gas you spilled.

From Tesla's web site:

Whenever possible, owners are billed per kWh (kilowatt-hour); in other areas, owners are billed per minute.

Supercharger Support

Learn more about Tesla Superchargers, including best practices, charging rates, payment methods and locating a Supercharger when you're on the road.

www.tesla.com

 

[ChrisMPK]

All businesses set their rates based upon their costs. When you buy a tomato at the grocery store, you are inherently paying for the cost of the tomatoes that fell off of the truck or were otherwise lost in production, regardless of what is listed on the label. Not rolling those costs into the price of the product would quickly lead to the tomato farmer and the grocery store going out of business.

Even if Tesla stated that you were only being charged for "KWH delivered", which they do not, the rate per KWH delivered would take into account the loss due to inefficiency. Either way, you are paying for the cost of getting electricity from the power plant all the way into your car, including all losses over the hundreds of miles of wire in between. For that matter you are paying for the interest to the bond holders that financed the power plant in the first place and for the insurance premiums that pay for the settlements to the victims of wildfires caused by the transmission line failures.

 

[Falcon73]

One thing I found today was that Tesla rounds up to the next kWh on their billings. They haven't been charging me for fractional kWh's. Two tests I did today in San Clemente showed 9kWh and 7kWh billed when the actual usage was 8.12kWh on the 9 billing and 6.70 on the 7 billing. I will see if I can test this further tomorrow.

 

[D.E.]

I don't believe Tesla has every claimed that Supercharging is the least expensive way to charge (unless your Tesla vehicle qualifies for free Supercharging.) Supercharging charging costs are pretty much on par with the cost of gas. When you are hundreds of miles from home, want to charge quickly what else can you do?

A few years ago Tesla claimed they had no interest in making money from superchargers. That changed.

 

[sleepydoc]

A few years ago Tesla claimed they had no interest in making money from superchargers. That changed.

How do you know that? When you charge at a super charger, you’re paying for not just the electricity but the infrastructure, as @ChrisMPK described above. The fact that they charge more for a dedicated, high power charging station than one might pay at home doesn’t necessarily mean that they’re gouging people or even turning a profit.

 

[shokunin]

a few years ago Tesla changed the calculation from what the battery accepted to what the pedestal was actualling outputting. Any in-car heating/cooling and thermal management should be included in the charging session. There were articles about it back in the day, a quick google showed this one

Updated supercharging billing

 

[D.E.]

How do you know that? When you charge at a super charger, you’re paying for not just the electricity but the infrastructure, as @ChrisMPK described above. The fact that they charge more for a dedicated, high power charging station than one might pay at home doesn’t necessarily mean that they’re gouging people or even turning a profit.

I’ve been reading the Tesla forums for over 5 years now. I’ve had mine for 4 years. There have been several changes in Tesla’s policies. Anyway I didn’t suggest they were gouging, just monetizing.

 

[sleepydoc]

I’ve been reading the Tesla forums for over 5 years now. I’ve had mine for 4 years. There have been several changes in Tesla’s policies. Anyway I didn’t suggest they were gouging, just monetizing.

Yeah, gouging wasn’t really a great word. They may be monetizing, or they may simply be minimizing losses. Initially, supercharging was free so there was no question of how much to charge. My guess is as Teslas have become more popular they are also incurring more costs associated with building out the SC network. And they can’t make money by overcharging for bad coffee and stale sandwiches like the gas stations do!

 

[Falcon73]

a few years ago Tesla changed the calculation from what the battery accepted to what the pedestal was actualling outputting. Any in-car heating/cooling and thermal management should be included in the charging session. There were articles about it back in the day, a quick google showed this one

Updated supercharging billing

This is exactly what I was looking to confirm. Thank you!

Now for my next question. Does the screen show what's going into the battery or the total? I will do some testing to verify.

 

[sleepydoc]

This is exactly what I was looking to confirm. Thank you!

Now for my next question. Does the screen show what's going into the battery or the total? I will do some testing to verify.

My guess is just what’s going into the battery since the car display is designed to show the car/battery status, but let us know!

 

[Falcon73]

My guess is just what’s going into the battery since the car display is designed to show the car/battery status, but let us know!

Will do. We are making a long Christmas drive today to be with my parents in the Desert this weekend. So I haven't charged it as much as I otherwise might, but it's still enough to make it in case no SC's are available.

She sips juice so slowly that I haven't had her below 50% yet, I don't think!

I will compare the billing with what ScanMyTesla shows, along with the screen. It's too bad I don't know of any wattmeters I could put in on the cable side.

Yesterday, I made a video showing the screen going up to $2.07 on a session and dropping down to $1.92 when I was done, so it seems it can round down too. Maybe I can figure out how to post it on YouTube.

Edit: Let's see if this works. I will plan to do another one today to try and see if it rounds up.

Tesla Supercharger Rounded to the Nearest kWh