I use one for my house. That way I don't have to worry about grid interconnect - use a growatt 12k off grid inverter, batteries, and solar. It's out in an outbuilding, though, with only one 60A set of wires, and one 20A set of wires going from the house to the outbuilding - otherwise I'd use the inverter's built in transfer switch, which is what I expect most people do.
Instead I have the inverter fed by the 20A from the utility power so I can do arbitrage if desired, and the output goes to a breaker that goes to the 60A lines to the house. At the house I have a 4 pole 100A ATS - one step up from the one you've listed. I used the one you show at first, but it eventually broke, leaving me missing one leg of my split phase. I had a transformer on the house side of the circuit (to balance the legs since too large a discrepancy would trip the older 6k inverter I previously used), so nothing broke, and we didn't even notice the leg had gone except some weirdness when on solar.
The failure of the ATS was weird - mechanical on one pole, the bar that moved and made contact had broken out of its holder, so was no longer making contact - so when I replaced it I used a 100A, and used a four pole - doubling the poles so each leg had two contacts. This not only spreads the load, but it increases the redundancy if another similar mechanical failure occurs.
The only problem with the larger 100A 4 pole ATS, though, is it switches more slowly, so while we had no devices that would reboot with the older two pole ATS, we have at least one TV which is reset during the larger 100A ATS switchover. If I cared I could put a UPS on it, but it's not important. Turning the balancing transformer back on would probably solve this as well, but with the new inverter we don't need it and it does consume power.
Notably, these cheap ATS devices are not UL compliant. I mounted mine in the top of the breaker panel above the main breaker, with utility coming on one side from the old breaker panel, and solar coming in from the right. It mounts on a DIN rail and I have additional 63A DIN breakers on each input to the ATS. It then feeds the main breaker of the new panel. It's inaccessible, though if I desired I could elevate it and provide access to the handle, or add a handle to the panel that attaches to this handle.
One thing about these ATS units, though, is you see the black cover over the switching area - these are vented, and when switching under load they vent live sparks out of the ATS. It was something to behold the first time I saw it, and the few times I let it flip back and forth dozens of times a second it was like a shower of sparks, and the vents started to deform due to the heat. It's what prevented me from cutting a hole in the front panel to allow access to the switch. Ain't nobody got time for live sparks thrown out into the basement. They still get thrown, but now behind the panel, inside the breaker box.
Issues with these:
- Not UL rated.
- They throw sparks out the vent when switched under load.
- There is no hysteresis. If you have them set to automatically switch (this is configured using wires to the solenoid control) you can make them switch back and forth dozens of times a second if you put a heavy load on the output, and the preferred input turns off under that load, then turns back on when the load is removed.
- They don't allow wire to be attached directly, but require a fork or ring terminal
But if you want a cheap ATS, and account for these issues they work well, and since the solenoid is a low current device connecting a wifi or other external controller (and adding hysteresis or other logic) is an easy way to switch heavy loads without using a power-hungry contactor.
Of course, a UL certified 100A or 200A generator ATS would be better in many ways, but they are not cheap, they take more space, and they are not as easily controlled externally without getting even more expensive.