Tesla supercharger claims I use twice as much energy vs my home charger

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Keep in mind the car might be preconditioning prior to arrival at the Supercharger. And if you're sitting in the car with the heat or A/C running that's more energy usage. Also the battery cooling system uses energy too.

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If you’re supercharging you’re probably roadtripping and racking up some miles. The charging probably tracks with the usage.

I have only ever supercharged my model 3 since new. Just recently I got solar and now it's cheaper to charge at home. The comparisons are for identical miles driven to work daily.

I never precondition just pull into supercharger and charge.

I charge in Monterey Bay area at night so the temperature is roughly 60°, I do have the temp set to 70° while charging. No preconditioning. My immediate thought was that Tesla is looking at my account and adjusting my price per KWH by saying I am using more energy than I am to charge me more money.

Well now I am truly befuddled

Ok well you probably should precondition, if you don't then your supercharging session will take longer as it will then start to warm up the battery once you start charging. The car needs a warm battery to charge fast so without preconditioning it will charge slow for a while until it has warmed up the battery (and you still "waste" energy to warm the battery, you are just waiting to do it after you arrive). Maybe you live in a area where that does not matter much though. In the winter in the midwest it makes a HUGE difference at superchargers. I also find it hard to believe your mileage was exactly the same. You didn't have to go out of your way at least a little to stop at the superchargers?

You're supposed to select the supercharger on your map so you're battery can precondition for faster charging. You're doing it wrong.

Supercharger location doesn't add to daily mileage, temp during charging is almost always 60° next to Pacific Ocean at around midnight.

Fully aware I refuse to recondition and have unlimited time to charge.

It's either DC fast charging is less efficient or Tesla is fudging the numbers for more profit.

Miles alone don't account for efficiency.

It's interesting that you wouldn't consider that maybe you're misunderstanding something here.

It's neither. You mentioned you refuse to precondition. That is why it takes longer at the supercharger and you use more energy there. It may be moot if you can now charge at home. But, there is a reason why the battery is preconditioned prior to the supercharger. The battery has to be at temp before it can be fast charged. Temp here is something like 90-100. If you pull up and your battery pack is 60, the supercharger won't charge quickly, it starts very slowly until the battery warms up. 60 is cold relative to what the pack temp needs to be. So, it uses more energy than is needed just to charge the pack, it has to also warm it up. Why would you not follow Tesla's recommendation. You have the time but you are wasting money paying for the supercharger to heat up the pack. It doesn't make a lot of sense to do that.

Yeah it'll still be much faster and better for your battery if you preheat your battery

This is terrible for your batteries. It isn’t just about faster charging. It is about efficiency and long term battery health. Constantly charging cold(at outside temp) batteries is bad for them. You’re way more likely to have failed batteries in the future. So my question is why do you refuse to precondition?

Tap on the kWh number and see if the scales change. I think it’s showing the *Cost* comparison. The numbers don’t change, but the bars will. Apparently there’s nothing to highlight which comparison it’s presenting (🙄 correction, right side changes to show units on the top number 😝). I just tried this with mine (from road trips, I don’t Supercharge otherwise) and the graph changed. Edit: it ***does*** show on the right side. $ or kWh, hard to see. Oh well.

Just to make sure, when you use the expression "preconditioning", you aren't talking about cabin temperature, correct?

For battery pre conditioning.

I am on my second battery and am ok with dumping car at 100k miles once car is out of warranty so pre conditioning is just a wast of money.

I feel bad for the poor soul who buys your car used in the future.

Nothing wrong with not preconditioning. The car will just charge slow. What does happen if battery is not at optimal temp is that extra energy from the charger is used to heat up the pack. So the cost for OP is probably the same.

The car is going to waste that energy anyway as you plug in. Teslas use extra energy to heat up the pack when you plug in.

Car will still heat up the pack by using extra energy to get the pack to over 105F while charging.

Preconditioning does more than decrease charge time. The reason why it is taking longer to charge is because it is inefficient when forcing the electrons and ions back to their original positions (cathode to anode) when not at optimal temperatures. On top of that when the charger is the one that needs to increase the temperature while charging the temperature of the batteries is less controlled. If the car gets the batteries at the right temperature before starting you will decrease the odds of battery problems in the future. Tesla didn’t add the preconditioning feature because it makes the charging faster. They added it because it decreases the amount of failed batteries they will have to change out under warranty.

It is the same system that is used to precondition the battery that is also used to heat up the pack when you plug in. Maybe a small amount of heat from the actual charging, but it is minimal. The BMS is designed to protect the battery and will not charge faster than what is safe. Teslas, and other EVs, don't even accept a charge if the battery is freezing cold. And people can't use a 120V outlet in winter if car is parked outside. The provided power is only enough to keep the battery warm. Even the 240V mobile unit is barely enough in many cases. If you intend to keep the car until it dies 15-20 years later then sure, it might make a difference if you precondition or not.

They do in fact accept a charge when cold. If you go to a fast charger during winter and plug in to charge it will start charging right away regardless if it was preconditioned or not. Also, I charge my cars frequently at home on both on a 120 and a 220. It being parked outside in the cold does not prevent it from charging. And sure if you plan on throwing the car away after a couple years then the problems you’re creating will fall on someone else in the future. Charging any battery that is not conditioned to be at ideal temps decreases the batteries life.

No idea what you define as cold. But a Tesla battery is not charging if its temp is below 0C/32F.

well this could be exactly it then. it will pull power from the supercharger to precondition the battery by running the drive motors inefficiently to increase battery temperature to optimal charging, or potentially be directing cold coolant to the battery if needed

Here is a side by side with each setting. Both home charging and supercharger are $0.32 per KWH https://preview.redd.it/1cgb1tpdohog1.jpeg?width=1470&format=pjpg&auto=webp&s=290993f2a3d0108f77ccb113d9e5a6f6da423d4e

It is interesting, I would expect Supercharging, being DC, would be more efficient, and so would be lower consumption (although not this much difference), not higher as this indicates. Makes me suspicious of the Supercharger numbers (which is your point).