Most of my stuff lives on a cheap hetzner vps so that power is someone else’s problem lol. at home it’s a raspberry pi that’s always on (a few watts) and a bitaxe miner doing about 19W, that’s around 14 kWh a month, like 3 euros here. the gaming pc is the only hungry thing and it stays off, the pi wakes it with wake-on-lan when I actually need it. took me a while to get the bios settings right (erp off, power on by pci-e) but it was worth it.
I’d add backup age and size, not just status, like alert if the newest dump is older than ~26h or smaller than 1MB, a job can say success and still leave you a useless file. and disk fill with a threshold, not only the graph. learned that one the hard way, a table on my vps was getting a row every minute with no cleanup and one day the disk hit 100% and postgres just died for like 40 min, obviously nobody was looking at the dashboard right then lol. now 80% warns and 90% sends me an email, and uptime kuma checks the cert expiry from outside. I guess the dashboard is nice to look at but the stuff that matters should ping you
What I do for that is turn it around, instead of checking for a failure I alert on the absence of a success. backrest has hooks, so on snapshot success it pings a push monitor in uptime kuma (healthchecks.io works the same), and if no ping arrives in ~26h it alerts. That way it catches the backup that never ran, which is the one that scares me the most I guess