Keeping tradition with doing things backwards, I’ve finally got a UPS for the rack (mounted in the bottom of the stack). Got a PowerWalker VI 2200R. Its a 2U unit which is all the space I’ve got left in the rack. Decent price and decent I/O with USB, serial and a slot-in for network expansion + 4 IEC outputs. Its powering everything in the rack and connected via USB to my main server which runs a NUT server that other machines can connect to. A calibration run (100-80%) puts the runtime at about 20 min. Long enough that I’m comfortable setting things to shut down when 20% capacity remains. Summary, I sleep better now.
Actually there are also simple “surge protectors” that do not have batteries, but will prevent most damage to electric equippment. However these will not prevent data-loss from unexpected shut-downs.
Most UPS also have an surge-protector built in though.