About half a year ago I bought a used UPS. It didn’t have enough output to power my main PC, but it’s perfect for my home server and network.
Starting on Christmas eve and continuing even today, my neighbourhood has been getting intermittent brownouts. It’s only affecting one phase (house is on a three-phase 240V connection), which happens to be the one powering my network (also all of the light fixtures, stupid Soviet house), and the UPS works beautifully. I didn’t lose any of my services even once. Without it, I would probably be reinstalling Proxmox and praying to the RAID gods to restore my hard drives.
“It pays for itself as soon as it is needed” is proven true once again.
I have all the expensive and/or critical (e.g. boiler) devices behind double conversion UPSes - those are the safest ones and also help with brownouts. They are cheap if you get them second hand and buy new batteries. 2000-3000VA units can be found for as little as 150 euro + batteries.