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Comment by dgacmu | Hacker News Reader

What's nice there, though, is that the total amount of _energy_ needed at a charging station is roughly fixed(), regardless of how fast you charge the cars. So if you're provisioned for the needed total energy inflow, you can to a reasonable degree compensate for having a more bursty high-rate charging load by having some amount of local energy storage as a buffer.

() - Assuming you provision for the highest-traffic-volume day. Ignoring potential induced demand of making it a little easier to drive, which I suspect is pretty bounded - people need pee and stretch breaks anyway.

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For numbers, just follow traffic at a busy gas station. Roughly 100 vehicles per hour is typical. So imagine having to charge 100 Teslas per hour, or just over one telsa per minute. That is still an insane amount of power.

That's not the math though. Approximately 0% of those vehicles at the busy gas station ever fuel up at home. Most of those EV fuel up most of the time at home or at a "Destination Charger" at places other than a roadside DC Super-Fast charger.

I see figures given that around 80% of EV charging is done at home (1). That doesn't mean that the other 20% has to be super-fast though, it will be less than that.

https://www.energy.gov/topics/national-ev-charging-network#

Only people with houses get to charge at home. All the non-rich who don't own houses are stuck with commercial chargers. It will be the reality for so so many people.

1) Do you dispute the 80% at home figure, and if so, on what basis?

2) Are you claiming that all "not at home" commercial charging is "busy gas station" style fast charging while waiting, and if so, on what basis?

Applying gas station capacity math to EVS as if they are like for like will give wrong answers. Your point about access to charge at home is valid but unrelated to that.

As others have noted, urban gas stations are likely to be far less busy in an EV world due to the ease of distributed charging -- home, work, destination, etc.;

But I think you raise a good model for long-haul. I think of the pennsylvania turnpike gas stations as a worst-case situation: They serve a somewhat captive audience, many of whom are traveling so far they need a mid-trip fillup. So something like 80kWh/minute _does_ seem like what you'd have to do for those specific stations, and that's an average rate of 4.8MW, at least during prime time.

You can probably get away with half of that if you use local storage as use is much lower at night. But let's not - let's see what it takes to do 4.8MW.

The answer is: You don't need a substation. You DO need on-site transformers and switchgear from 12kV primary service. But to put it in perspective, 4MW is like a tiny datacenter or really big (new york size) office building. So it's not really too crazy to think about an EV per minute going from 0-80kWh in a dedicated area. Compared to huge underground gas tanks, I think the infrastructure part of it is pretty ok.

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