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Comment by thatfrenchguy | Hacker News Reader

> Converting a gas appliance to a heat pump, for example, would draw 4 to 6 kW, while an L2 charger for EVs would be 12 to 14 kW. A

This article has an issue with numbers here clearly. A heat pump isn’t really going to consume more electricity than the AC it replaces (and hopefully it is more efficient than the cool-only-AC it replaces as well so electricity uses decreases in the summer).

For electric cars, no-one needs 48A (11.5kw) charging (unless you bought a hummer EV and then you’re an idiot). The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up.

Palo Alto also does not have TOU plans, and no demand charges.

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They're specifically talking about replacing gas appliances with heat pumps -- e.g. heaters. A moderate sized 3-ton unit uses around 5kw to heat on cooler days where a gas furnace might use 0.1kw to turn the blower motor.

I live in a weird house that has 3 gas furnaces but only one of of the furnaces has AC attached at the moment. I'm going to swap out two of the three for ducted heat pumps, so my peak electrical load in both seasons will increase by roughly 5kw. Replacing the third furnace (with the AC) would surely reduce the cooling electrical load since it's old and outdated, but would add another few kw to my winter heating load if I were to do so.

FWIW, if you use 2.4kw charging (Level 1, typical for a household) , it may take multiple days to recharge your 80kwh battery. Charging overnight, for example, it would require three full nights to get back a complete charge.

While this wouldn't be a problem for most folks, there are definitely many who could easily outstrip the power provided by a Level 1 charger (in my area, construction workers who are driving around 100 miles per day to their worksite is an example).

Also, you need a minimum of level 2 charging to support long distance travel by road, where a full battery can be consumed in about 3 hours of highway driving.

Did you reply to the wrong comment? OP said nothing about L1?

Nope, right comment.

> or electric cars, no-one needs 48A (11.5kw) charging

refers to L2 DC fast charging. The next level down (which is implied by "nobody needs L2") is L1 charging, which is done on a household 120V or 220V circuit.

In other words, if you don't supply L2 (and L3) DC fast charging for customers who need it, EVs will never replace ICE.

No, he's saying that 24-32A charging is enough.

> The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up.

32A at 240V (the standard for DC fast charging) is ~8kw, so you'd still be looking at 10 hours for a battery charge. Sufficient for my construction workers, insufficient for supporting long distance driving.

I think we can agree that anybody who averages more than 400 miles a day is going to need more than 24A charging. Commercial drivers should be using commercial facilities, not residential ones.

Anybody taking a road trip falls into this category. You couldn't drive from San Francisco to LA without access to L3 charging.

Both 24A and 48A charging are both similarly insufficient for a road trip, so I'm unsure how your comment relates to thatfrenchguy's original comment.

His original comment says no L3 capable charging should be allowed, with the only exception requiring a huge investment in expensive battery storage (Lithium Ion packs cost around $200 per kWh, built at a MWh scale) - something unprecedented with gasoline infrastructure.

Can you link to the comment you're referencing? I can't see where anyone said that.

The original comment says nothing about L3 charging. It says nobody needs 48A charging, which is a type of L2 charging.

Even 11.5kW is not DC fast charging. That's still an AC charge typically.

FWIW, I'm using the following as my guide for what level each kW is:

https://www.jdpower.com/cars/shopping-guides/what-is-dc-fast...

And 11.5kW is in the mid-L2 range per that. It could be out of date, for sure.

That's a good guide, but L2 is standard AC charging (usually with a 240V outlet in your garage/driveway) not DC Fast Charging

A good point, thanks!

You seem to be confusing a lot of terminology. DC charging is a separate thing from L1-L3, though some people mistakenly describe DC charging as "L3".

L1 = single phase 120V power. People typically think of common household outlets, which will be limited to 12A or 16A, but it could also be a TT-30 at 24A.

L2 = Split phase 240V. Typical amperages are 32 and up, but lower is possible with some cars and higher is common. Eg, the F-150 Lightning can charge at 80A.

L3 (very uncommon) = 3 Phase AC at up to 400A - Could be >300KW. I've never seen this.

From that article: "Both Level 1 and Level 2 charging utilizes alternating current (AC)"

You're confused. L2 is not DC fast charging, it's just 240V AC charging.

Most home chargers will likely be 240V at ~24 Amps, that's about 6 kW and plenty for the vast majority of users. People who regularly need more can easily install more.

DC Fast Charging, (L3) is done at 400-800V and really only needed for road trips so few places outside of highways will likely have it

He was referring to reduced amperages, not switching down to single phase (L1). It'd be enough for most people, but significantly less peak load.

> For electric cars, no-one needs 48A (11.5kw) charging (unless you bought a hummer EV and then you’re an idiot). The city can start denying permits for charging at more than 24-32A unless you have enough battery storage to cover it up.

You're wrong about this. We frequently take day trips that are about an hour each way from home, and without the L2 we would get dangerously low after another day of commuter driving. As a co-poster noted, standard chargers will take days to recharge. Ours does about 6 miles of charge / hour, whereas the L2 does about 30 miles of charge / hour.

What kind of vehicle & miles do you have where 24A charging isn't enough?

A 7.2kw level 2 charger using 32A is pretty standard, 24A would be slower than I'd want for daily use, and I own an older Leaf. Even at 32A, it's slow when you need to charge quick for any reason (top off for afternoon errands, etc).

I have a 320 mile range, so I never need to top off for afternoon errands.

Naively you'd think that cars with a larger battery would be more likely to need a level 2 charger since it takes so much longer to charge a large battery on L1 than it does a small battery. But in fact it's often the opposite -- a big battery means you only need enough charger to handle an average day rather than a peak day.

Which is why the OP includes 32A=7.7kw charging, which is what Tesla's get. OP is only really against insane installations where you charge at 48A=11.5kw, that's the capacity of 1.5 Teslas, and is only really necessary when you're running a horribly inefficient Hummer EV (200 kwh battery getting 350 miles EPA range means it's operating about 600 wh/mile or 1.6 miles per kwh, twice the energy usage of a Model X).

One option is to have charging speed limits based on state-of-charge.

Maybe charging after your daily driving only charges at 3 kW, but charging after a road trip does the full 11.5 kW.

But yeah, I've certainly come home from a road trip with 10% battery, plugged into my 11 kW home charger, and had it say it would take 5 hours to recharge to my 70% limit. If I was only charging at 2 kW, an overnight charge wouldn't get me very far the next day.

But how often do you need to go far the next day? If you come home with 10% charge (30 miles), and then plug in for 10 hours and add another 40 miles, is that not enough for work and errands the next day?

I don't know about you, but I mostly do long trips on the weekend. As long as I have enough to get to work Monday morning and am full by the weekend, that's almost always good enough for me.

The average commute distance is 41 miles, 10 hours of slow charge is a net loss.

"Frequency" matters significantly here, while charging at home is an extreme convenience, you might expect to stop at a charging station if you fall out of bounds, like with a 250 mile trip 1 day and a 100 mile commute the next day (each without a charging stop connected with any bio breaks)

It's definitely something Tesla has solved for to achieve their cross nation road trip planning with 0 home charging.

EVs almost never need 48A charging, but for times when they do, it’s what makes EV only households practical.

The answer isn’t to ban high AMP L2 chargers but instruct cars to only use high amp when lower amp charging isn’t sufficient.

For most users who do home charging, they leave them plugged in for 10+ hours at night and drive nowhere near their battery’s capacity, so trickle charge them each night, ensuring car is ready at their scheduled departure time.

TBH, 11.5kw would be enough for most people with a Hummer EV too. It'd still gain ~50% overnight. It could keep up with a 100 mile commute.

Your quote from the article explicitly says converting a gas appliance (e.g. a water heater) to electricity increases electricity consumption, which is obviously true so I'm not sure why you take issue with the article?

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