If that wikipedia article is right, then balcony solar is not legal where I live (in the US). Here, we require a hard-wired, permanently installed automatic transfer switch that disconnects the solar generation from the grid when the mains power goes out. This is to protect line workers when working on downed lines.

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hamdingers 4 hours ago | parent | next [-]

It's probably coming soon for you, 30 states have bills announced or introduced legalizing plug-in solar and one (Utah) has already passed. They should be fairly uncontroversial.

Also, there's no need for a transfer switch in any grid-tied system, whether plug-in or hard-wired. Grid-tied inverters shut off automatically if there's no grid frequency to sync to.

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jacquesm 2 hours ago | parent [-]

That simply is a transfer switch that is built in.

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hamdingers an hour ago | parent [-]

What would it be transferring the load to?

"Transfer switch" refers to a specific kind of switch that transfers load between two sources. There is only one source (the panels) and one load (the grid) on a grid-tied inverter, so what you're saying does not make sense.

There are more complicated solar setups that do involve transfer switches, but they are not applicable to the balcony solar use case and remain uncommon even for hardwired rooftop solar.

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jacquesm an hour ago | parent [-]

In grid tied inverters with batteries the transfer switch can be built in to the inverter or it can be an external switch that the inverter talks to. Similar to how you would use one with a generator setup.

And indeed these are uncommon, mostly because they tend to be more serious devices. Victron and formerly Xantrex make nice ones, but the inverter alone probably costs more than a complete balcony solar installation.

For the solar balcony and more common rooftop solar setups there is only a simple disconnect, but both a transfer switch and a disconnect are the same thing: a (usually beefy) relay, but the transfer switch variety switches your house between the inverter and the grid whereas the disconnect just physically disconnects the inverters output. The downside of that setup is that if there is no grid but you do have solar that you still have no power.

Most of these wouldn't be able to power anything but the smallest installations anyway (300 W or so, typically), and don't have a battery to store any excess (as if there would be any...).

As soon as you add a battery it makes good sense to use the transfer switch: you can disconnect from the grid but the inverter can keep running to power your house and if you're lucky the solar will replenish it fast enough during the day that you can hold over for a while.

The big rooftop inverter that I have has a built in transfer switch but I'm not using it right now simply because I don't have a good way to route the wiring to and from the inverter. It is stuck in my garage with the main distribution panel on the other side of the house. In my old house in Canada that was all designed from scratch and there we had the house entirely off-grid with the transfer switch hooked to a genset if the power was out for longer than the battery could sustain us (48 KWh so that usually was good for a couple of days).

	▲	hamdingers 42 minutes ago \| parent [-]
		A disconnect and a transfer switch are not a same thing, "transfer switch" refers to a specific type of switch in a specific role as I have described. Conflating the two is incorrect and benefits nobody.

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jacquesm 2 hours ago | parent | prev [-]

99.9% of all inverters currently being sold has this functionality built in. That 0.1% remaining you will find in the second hand market and the bargain bin of Amazon.