this post was submitted on 16 Jun 2025
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One thing I really don't get in the discussion around EVs and charging is, why are people so afraid of tripping the main breaker? If you have a total of e.g. 17 kW available and happen to go over, just reset the main breaker (or replace it in case it's still a traditional one). It's there precisely so that you wouldn't need to care about overloading the connection.
In my experience people get by with a 3x25A (17 kW available, matches approximately a 70A service in the US) while using the available power to
While it's true you can trip the main breaker if you have everything on at the same time, typically it never happens even if there are no lockouts in place preventing overuse. And it's not like tripping it causes any permanent harm.
Why is an electrical service upgrade constantly brought up as a solution when any home with >15 kW of available power won't need it? Is it against code to purposefully overcommit your mains in the US or something?
Edit: there were valid concerns raised over how long-lived the breakers are (probably won't be rated for tens of fault-condition related trips), also that these smaller service specs aren't as common as I've gathered from the media. That might have something to do with this at least. Thanks for the replies – it's been an interesting discussion.
The way that it works in most countries is that the breakers are per circuit in your wall. The breakers trip in order to prevent that single circuit from overheating and starting a fire in your walls.
Let’s say you have a wire that’s rated for 16amps. More than that and it becomes a fire risk just threw overheating. @230v that gives you 3680w per circuit.
If you have your industrial microwave, water heater, and car charger all going at the same time on that same circuit. This will draw way more than 3680w and thus would go over that 16a limit.
The breakers trips once you go over that 16a limit for safety. It’s a good thing. This all being said no sane electrician would put those three things on the same circuit. lol.
Circuit breakers are actually what enable you to safely over provision. Without them fires would just be a matter of time.
I know it works this way in the U.S. and Germany at least.
Also worth noting that breaker ratings are for instantaneous usage. A 15A 120v breaker can only actually support 12A of continuous usage. But it says 15, because most things use a little extra power when they first turn on. AC system spinning up the fans and compressor, for instance. Spinning things up takes more power than keeping it moving. If you put a 15A device on a 15A breaker, it would likely trip as soon as that device turned on. In that instance, you’d likely use a 20A breaker to support the 15A device instead. But that 20A breaker would also call for upgraded wiring and outlets which could support 20A.
Ok – that works a bit differently for our code then. Standard breakers are 10 A and 16 A, which means 10 A and 16 A constant load. Load characteristics affect which profile you use, typical residential alternatives are B and C profile breakers. B trips quicker, C trips slower and is meant for circuits with more reactive load characteristics. 16 A C profile breaker can take up to an hour to trip under 18-19 A load as an example. Your standard breaker can deal with quite a lot of inrush current – even with the faster B profile.
Wiring is built to withstand approximately 15 A when using a 10 A breaker, and 20 A when using a 16 A breaker. As such, the fuses display the value for constant loads, not for the peak. The most commonly used outlets in the EU (i.e. Schuko) are rated for 8 A continuous, 16 A peak, and are typically put on a 16 A circuit. 10 A circuits are mainly used for lighting nowadays, at least in Finland – 16 A being the standard for most things.
The voltage difference might have something to do with this, as 230 V will be capable of driving much more power though a potential short. As such any actual fault condition will most likely cause the fuse to trip quite quickly. Also current code mandates GFCI on all outlets in a house, which will help with smaller faults that aren't enough for the breaker to trip.