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by bhhaskin 1347 days ago
GFCI and AFCI are great! But a home isn't going to burst into flames or explode without them. Which is why there are exemptions.

240v at 30A is most definitely not a trivial load. Most homes have 100 amp service. That would be 30% of your homes total power capacity just for changing EV. You wouldn't be able to run AC and the dryer and charge an EV at the same time at that rate. But more importantly there is only so much power at the pole.

3 comments

They might not burst into flames, today, but these technologies weren't invented because there was no risk.

> That would be 30% of your homes total power capacity just for changing EV

That's the thing - most people have a 8 to 12 hour window to fully charge their car(s) overnight and when you and your neighbors are using practically no energy. Worst case is there is no active management and there is just a new peak at midnight. Best case is that the electric company incentivizes you to not only charge at non-peak times, but also pays you to allow them to manage the charging times.

This technology is not science fiction - it already exists. I got a $250 rebate from my electric company to install a connected level 2 charger. It is not currently managed, but if there is some dystopian future where all of my neighbors aren't burning hydrocarbons, all have EVs, and somehow the infrastructure hasn't kept up, as long as my car is fully charged in the morning, I don't care if it happened from midnight to 2 AM or 4 AM to 6 AM.

But also...

> Most homes have 100 amp service

Most homes built decades ago, maybe. And to be clear, we're talking about US 120V system. I would be very surprised if any house built since...lets be generous...the 1980s doesn't have a 200A supply or couldn't easily be updated.

Your recommendation would require updates to the NEC to even be considered.

As it stands today, an EV charger (or an outlet designated for EV charging) is considered to be 'in use' 100% of the time from a loading perspective (i.e., when counting how big of a main breaker you need to handle). Which, honestly, makes sense. You can't predict when other loads are being used reliably, and you can use an EV charger for many hours. For, say, during the middle of the night.. there's a high heating load so that loading will happen simultaneously.

There are more intelligent ways to handle this (and, the products exist today!), however they're quite expensive. Maybe less expensive than a full new overhaul of your house's electrical... but eventually electrical needs to be updated to code.

Also, regarding 100A vs 200A main panels: it heavily depends on the size of the house. I know in my neighborhood, which the oldest house was built in 2008, they only gave 100A panels to houses that were ~1700sqft or smaller. For larger houses, those got 200A panels.

It seems that this 100/200A thing might just be very different across even just North America, nevermind Europe. So much so that we can't make a general statement either way.

As in no, it does not heavily depend on size in general in the way you describe. It may do so where you are but that's about it. My house is smaller than 1700sqft, was built quite some years before 2008 and we have a 200A panel and I don't know what I would do with 100A service. It would be impossible actually. But that might be because we use electric baseboard heating and thus lots of heating circuits with quite a bunch of amps in use by that.

All houses in this neighborhood use natural gas for heating and stove/oven heating, so they have minimal heating load in the winter in terms of actual electrical consumption, and you get rid of the 50A oven outlet.

In general, electric heat is a bit of a menace in terms of electrical consumption... especially given electric prices lately.

Which is exactly my point. For your reality the reasons you gave make sense for why 100A may have been standard even in 2008. It does not generalize well to an entire continent or two though.

I live way too far out to have natural gas service and because I have such a small house it has baseboard heating. Most larger houses here have electric furnaces instead. But having 200A service meant I was easily able to add a mini split heat pump taking care of heating most of the time but we have no space to put a furnace instead. We do have propane to heat when power is out (or just if I want the nicety of a roaring fire heating up the room on -40 evenings). The oven is electric too. I was looking at getting a tankless water heater but would need to upgrade the electric service for that apparently because my 200A are not enough in case "everything else is on at the same time" (I personally wouldn't mind the heaters shutting off for 3 minutes while I take a shower but I guess that's against code).

Also electricity prices do not generalize well. Way too much variance across an entire continent or two. What you say is expensive for you actually isn't that expensive here. Now ask someone in Europe this winter what they think about your electricity prices in comparison.

When I moved into my home the first major upgrade I did was upgrading my electrical panel. The home was built in the early 80's and had a 100amp panel.

Putting in a 200 amp panel ran me about $1,000. Power company checked off on it and upgraded my meter in the process. I also added a 240v 30amp socket in the garage for things like an EV, and put a whole house surge protector on in the process.

My house has rock solid power at every socket and plenty of capacity for the future as well, definitely worth the investment.

> GFCI and AFCI are great! But a home isn't going to burst into flames or explode without them. Which is why there are exemptions.

True, but not what you said. You said the changes are not safety related, but these are safety related.

Keep in mind 240v @ 30 amps = charging at 30 miles per hour or so. Common daily driving (12k miles a year) = 33 miles per day. Even throttling to 10 amps (which my charger supports), is 11 miles per hour or 110 miles per day if you charge for 10 hours.

Having had a 100 amp service, it was really not a big deal. Sure I'd normally charge at 11pm, when the AC wasn't running. But the home is using WAY less electricity than when I bought in 1994 when TVs consumed a ton of power, single paned windows insulated poorly, a fair number of 300 watt halogen bulbs, and tons of the 100 watt incandescents. Between LED lighting, a more efficient refrigerator, and a MUCH lower power flat panel TV our power use per day is less than it was in 1994, even with a EV.

100 amps @ 240v is a ton of power, and if you need to peak shave there's quite a bit of room between 240v@30 amps and 240v@10 amps which is plenty for most normal driving patterns.