I have ordered one to try as an experiment. It will be able to power the PC + screen, router and modem, but not an old laser printer (too many watts) that is connected via Ethernet to the router. I will try it powering just the modem and router first. The printer is powered off unless in use and could be disconnected most days.
Recalling neutral experiments reported here with batteries, I am not optimistic, but printer aside it can power all directly or indirectly connected devices. My hope is that the odd burst errors that I get about every other day or so and come with about 10 ses may be reduced.
I have found that the v old florescent tubes in my garage which flicker a lot to get started can and do produce such spikes so there is an obvious test with them as a test source of noise. Of course the interference may not be coming through the mains.