Not really. In your case, you probably have a very high quality pure sine wave inverter that's much larger than the individual UPSes, which will make the downst

Not really. In your case, you probably have a very high quality pure sine wave inverter that's much larger than the individual UPSes, which will make the downstream UPSes mostly happy as long as you don't approach max load. Many cheap inverters are not pure sine, and a UPS seeing this waveform may decide it needs to go to battery also. Practically, a UPS also adds to the current draw, and many people may accidentally exceed the circuit limit because they only look at the useful load but not also the UPS charging load after a power failure ends.