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Comment by t0mas88 | Hacker News Reader

There is a real safety issue with plug-in solar panels and plug-in batteries. Things go wrong if other loads are on the same circuit, which is almost unavoidable with a plug-in system.

Consider a circuit in a home, designed to carry 16A like a common EU/UK circuit, protected by a 16A breaker. Then plug in solar or a battery that delivers just a small 10A. Now in case some other thing on that circuit draws 26A, the breaker doesn't stop it and the circuit is overloaded.

If that same solar was installed as a fixed setup on its own circuit with no other loads on it, it would be safe and protected by the 16A breaker in the switchboard. It's the combination with other loads that causes issues.

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My understanding is that is why they are limiting to 800w (~4A) at least in the UK's BS 7671 Amendment, which they consider well within the designed safety margins.

Hopefully nobody thinks "I'll save even more if I get two!" and plugs them both into the same circuit.

Perhaps they could somehow detect each other and shut off.

I think that's the reason why the total allowed panel power is only 800W, any more than that and you have to get it properly installed. At least that's ~ the way it is in Austria, it's also pretty easy to check whether you have ~800 or way more hanging on off your balcony.

Ah yes, the good old "let's eat into the safety margins". This is why our motorways no longer have hard shoulders. OK, so cars break down less now. What justification is there for eating into electrical margins? The wiring in people's houses isn't getting any younger. And we still use the ridiculous ring system even in new builds in 2026.

Estimates suggest they could save U.S. consumers billions of dollars a year in electricity costs, while potentially offsetting thousands of megawatts of demand (https://www.sciencedirect.com/science/article/abs/pii/S09601...)

Plus it increases equity because this primarily opens up solar for those in rented accommodation and apartments/flats who otherwise couldn't access it. Personally that feels well worth pursuing if it's deemed safe.

Great, but electricity is really quite dangerous and eating into the safety margins seems very short sighted. I've seen all kinds of horrors in home wiring. This might seem fine in a world where all wiring is completely up to standard, but in the real world it's done by busy electricians or clueless DIYers. The safety margins are there because in a real installation something will probably be not quite right. It's very common to find wires buried in insulation (the insulation installers don't know or care about electricity), wrong size breakers in use, old/worn out breakers/RCDs, loose connections, the list goes on...

So the danger comes when you plug the solar into a wall socket but there are other devices connected to the same fuse of circuit breaker. So...

Instead of the solar having a plug that goes into a wall socket, why not have a plug on it that screws directly into the fusebox ? Then you know that it is the ONLY device on the circuit.

Then a homeowner can’t install it themselves in 5 seconds for free, take it with them when they move, etc.

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