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Comment by cjrp | Hacker News Reader

The UK previously didn't allow small plug in solar panels (the kind that you just plug in to a mains socket) due to, I believe, safety reasons. This has changed within the last few days https://energysavingtrust.org.uk/solar-roadmap/

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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.

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.

It hasn't changed... yet. The media noise is because the government has announced that they were reviewing current rules with the aim of allowing "balcony solar" by the end of the year.

I believe it’s only legal in Utah so far in the US: they legislated it last year, and apparently half the country is expected to pass a copy-paste version in their next sessions

Current state by state status (not my site): https://pluginsolarusa.com

Plugin solar doesn't make much impact anyway even in Germany because of shades/angles and most of the time- no storage. Rooftop is another discussion

My balcony solar produced an average of 5kWh per day in the last month. That is about as much as I consume.

and did you consume it when it was produced?

I guess I consume most of it. There are 4kWh of batteries connected to the panels. I set my dishwasher and my washing machine to run when production is high.

so you have a ±2k eur battery on top of probably 1.6Kw solar modules costing about 1k eur, attached to balcony and generating about 5kwh/day? And probably with very nice sun conditions because otherwise you'd need more solar.

Now let's take french household prices per kwh of 25ct/kwh. It means at 5kwh/day consumption the bill would be 450eur/y. So a 3k investment in this case would pay for itself in 6-7 years.

For a german household with highest prices in EU payback would be in about 4y assuming 40ct/kwh

But realistically many will not even buy a bess not being able to capture all solar output and many will have worse solar conditions. I'm not sure balcony solar in Germany generates even 1% of total solar production in the country despite streamlined installation process

The batteries where 800€, the panels about 400 and the inverter I think around a hundred (all from Amazon). All the stuff I needed to attach the panels to the balcony and the cables where surprisingly expensive.

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