Half the problem with home-generation is a cutoff/sync device that synchronizes the frequency of your local generation with the grid, and kills power going back into the grid from your home generator when there is an outage, so line workers can do their jobs safely. And unless there is a more expensive/complicated device that can 'smear' the frequencys between the two systems slowly so they match after a disconnect/reconnect, most of these systems will shutdown local generation if there is no reference frequency from the main power feed.
I think it's a neat product, a UPS that doesn't look like a computer peripheral, that has large enough capacity to be useful for important appliances like fridges, that can be integrated into common spaces, and with some kind of management utility that can ensure the battery health is monitored.
If you backfeed during an outage, and then the grid reconnects, you're fighting the grid. If you backfeed during an outage and an electrician is trying to fix lines near you, you can hurt them.
Why does the OP say it "disconnects in 20 ms of detecting an outage"? If it's a UPS, it doesn't need to disconnect - It's just no longer fed by the grid. If it's back-feeding, the point would be to _start_ the connection when you detect an outage. But backfeeding is an extremely bad idea.
Yes, plus an auto-transfer-switch
Yes, exactly.
> is that what the tesla "Wall" is?
You mean the Powerwall. It's more like a standby generator than a UPS, because they either backup the whole house, or a subpanel. There is an automatic transfer switch, just like a standby generator.
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The big differences between a Powerwall and a standby generator are:
The Powerwall needs no maintenance. (Standby generators need annual maintenance, oil changes, new spark plugs...)
The Powerwall needs no external fuel source. (No tank of diesel or propane, no need to have a natural gas service to the house.)
The Powerwall can be configured to only charge from solar. This allows owners to take advantage of renewable energy incentives.
The Powerwall can join Tesla's virtual power plant, and feed back into the grid, thus generating revenue. (Basically, charge from solar when demand for electricity is low, and feed back into the grid when demand for electricity is high.) Tesla paid me over $1000 for 2024.
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(In case you didn't know, a standby generator is the kind that automatically starts and powers your house in a blackout. A portable generator is, well, portable. If you have one, you have to manually start it, and either trip over extension cords, or wire in a manual transfer switch to your house.)