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Comment by kylec | Hacker News Reader

I'm kind of surprised that they're so adamant that the pricing should be hWk based. It seems to me that time-based pricing would have made sense - Superchargers are a limited resource, so a time-based approach would have encouraged people to only charge for as long as they needed it. Above 80% a Tesla charges much slower, so it uses much less electricity, but it still takes up a stall.

It would have also dovetailed nicely with the per-minute fee they will be charging Tesla owners for leaving their vehicles plugged in after they're done charging at busy Superchargers.

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They should stop fighting market mechanisms and do dynamic pricing. It's obviously the way it should be done. Price should change upon the cost of the underlying electricity and there should be surge pricing once queues form to discourage overcharging during peak usage.

Elon is normally so smart I don't understand why he's fighting the math based approach here.

People like predictable pricing. You sign a lease rather than renting month to month so your housing can't double in price just because. If it can cost between $0.50 and $500 to "fill up" your Tesla, that would SUBSTANTIALLY alter the way owning a Tesla is perceived.

People also like being able to get an uber when they really need one instead of relying on cabs that never show up on Friday nights. The cost of electricity to completely fill up a Telsa is between $5 and $20 depending on time of day and where exactly you are in North America. With 1-3x surge pricing call it $5 to $60. If you're filling up half a tank (say from 25% to 75%, the fast charging window) that's going to cost you $2.50 to $30, and usually around $10. This isn't even worth thinking about it for current Tesla owners.

Most people really hate this kind of pricing. It would combine badly with "range uncertainty" for people who've not yet bought one: not only do you not know how far you can go, you don't know how much you'll have to pay for it either.

That's true for petrol engines, though. The price fluctuates, though not generally wildly, and I know -for example- that it will cost me $25-$30 to fill up my car.

I imagine the fluctuations of the electrical grid are no different and likely more stable. It would make sense to charge more during the day when there's a higher load on the grid anyways, and considering the price of Teslas, I am confident the owners can afford it.

The charging rate is very low when there are many Teslas charging at a station so sometimes it could take 3-4x longer than usual when at a busy location. I'd expect to be charged the same amount in those cases.

Why would you expect to pay the same? The resource is in higher demand. California has peak demand pricing for electricity to homes, why would this be any different?

Curious they don't catch more coverage on this fact as it seems to directly contradict the narrative of a "super-charger". What prevents them from being able to charge all ports at full power?

This seems like another notch on the long list of hidden caveats with a Tesla. Other examples being constant surveillance/telemetry and the thermal battery throttling (0-60 in 2.xx seconds but good luck maintaining that!)

To be fair, "very low" is like 220 mi/hr compared to standard 360 mi/hr based on my experience.

They do have a disclaimer on charging rate: "Charging from 10% to 80% is quick and typically provides ample range to travel between most Superchargers. Charging from 80% to 100% doubles the charge time because the car must reduce current to top off cells. Actual charge times may vary."

https://www.tesla.com/supercharger

>What prevents them from being able to charge all ports at full power?

Capacity of the substation or the cable linking the supercharger to it.

Not sure why this isn't possible. I learned this the hard way last time I spent 8 hours driving to LA from the bay area during the holiday season. If I was in a hurry on holiday to get to socal I'd much prefer driving a regular car with gas. The capacity at each charging station is visible from the map though.

You can opt out of them storing data about you. Even if you are the only car at a supercharger, it slows down the rate as your battery fills to protect it. It charges as max power (120kwh) when your battery is pretty low. However, the net effect is vastly faster than all other battery charging systems. Leafs lose range quickly if you charge them with chademo a lot, because they never cool the battery down to keep it from overheating during charging.

I think that behavior is built-in to the way most people value their own time. There is no way I'd feel like I was gaining something by my vehicle charging slower - even if I effectively pay a lower per-hour cost.

The incentive to not charge above 80% is that it is harder on the battery, and those things are expensive. So that's a good incentive to charge in the sweet spot. Though my delivery guy said there was someone doing deliberate 100% charges trying to get his pack degraded to the point where Tesla would replace it, but he's been unable to get it to degrade the extra percent or two to 6%, so maybe it is harder than they make it out to be.

To eliminate this, in many cars "100% battery" isn't really 100%, so that users can't accidentally "mis-charge" in a way that deliberately degrades the pack.

For example, a Chevy Volt has a 16.5kWh battery, but a "100% full" Volt charge only uses 10.4kWh of that.

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