I would highly suggest a UPS. I use random external hard drives without RAID as part of my media setup. The electric went out overnight last year. I knew it had happened as my oven was flashing. The server restarted itself so thought everything was fine.

Then some things were glitchy and it took me a few days to release one of the drives was not mounting. Luckily I did not lose the data but it still took a while to fix. It takes even longer to restore a backup.

To mainly save myself time and effort, I bought a basic UPS with 2 plugs. It keeps the server and main router on for 15 minutes but I’ve set it up to send a command to shut down asap just in case. My server seems to automatically switch on when power comes back so not had any issues since.