Hey experts, I'm trying to figure out my ideal home charging scenario. I know charging slows as charging progresses but does it ultimately use the same amount of power? At a supercharger billed per minute, charging 80-90 percent would cost more then charging 70-80 percent. Is there any truth to this at home? Is your car able to consume every ounce of energy it is given? Or is there any wasted energy consideration ? Does that make sense? Thanks!
I think you are mixing up a lot of the basics, but here goes.
There is heat loss, regardless wether you charge at home or at a Tesla Supercharger or any other DC fast charger. But there is a difference in how much energy you are loosing during the heat loss and it depends on a lot of factors - battery temperature, cable type, AC or DC, kW speed.
It is hard to tell really what your heat loss at home will be, without knowing the setup, but as a general rule of thumb, charging slower results in more heat loss. Now, if you have solar panels, you wouldn't care much, as it is "free", but if you don't, you can calculate anywhere from 15-20% more energy you have to pay for than it gets into the car.
I will give you some examples - at around 2-4.6kW home charging I am seeing around 14% heat loss. The best I have seen is around 12%, but I believe the Tesla Wallbox is around 14-15% also.
This means that in order to put 70kWh in your LR, you will pay for 80kWh. You can easily measure that by using a Wallbox with a kWh counter or if you have a regular plug then put a separate electric meter behind the plug and measure just that plug and calculate the difference. But if you go with 15% you will be safe. I have seen around 20-25% loss, but this is a bit more extreme and with low Schuko 5A charging.
On a DC Tesla Supercharger(or other HPC DC charger) the heat loss is less, because there is no AC to DC conversion like with the slow AC Wallbox and the loss is mainly with the cables or around 8-10%. Tesla covers that so even if they charge per kWh like they do in Europe, you still only pay what you get, the heat loss is covered by Tesla in the kWh price. Meaning if you charge 20kWh inside the car, you pay for the 20kWh and Tesla covers the other 2kWh extra from their pocket.
Yes, going above 95% will probably result in more heat loss, but 5%(95-100%) is around 3.5 kWh so you shouldn't worry wether you pay for 4-4.5kWh instead of 3.5kWh. You shouldn't go above 80% often either. Maybe 90% once and a while.
Also, slow charging is better for your battery, so you should consider wether 5-10% more heat loss at your kWh prices is worth it, over a shorter life span of the battery(spoiler alert - yes, a new battery is more expensive than a few cents extra every charge)
So in the end - charging at home will result in about 15% more kWh than it goes into the car.
Hope this helps.