Are you using NUT-server and reading it to Grafana? Would be interested to know the workflow here.

This is my sloppy garage homelab.
A lot of this is hand-me-down, free, or very cheap ex-office equipment.
Top to bottom:
* Router is an office salvage Lenovo ThinkCenter M710 i5-7500 with 8gb RAM and a cheap Intel NIC running PfSense.
* The switch is a HP 1920-8G
* The Raspberry Pi 4 is running Network UPS Tool server, and reading the two UPS (we’ll get to those later). In the future I’d like to have it work as a Serial Server and control the drive boxes.
* The main server is an office salvage Lenovo ThinkCenter P310 with an i5-6500, 64gb ram, an added HBA and SFP NIC to connect to the switch. Running Proxmox, with a few VMs, notably a LXC with my Cosmos-Server and most of my web apps, and a TrueNAS VM. There’s 4TB of cheap used samsung drives in ZFS Raid 10 (not sure the proper naming) where the LXC and VM live.
* This is all sitting on a CP PR1000 that came for free from a VFX studio shutting down.
* The two drive boxes were free from the same studio. 36 of 48 bays are populated with 4TB drives ranging in running age between 1 and 5 years. The TrueNAS VM has direct connection to the HBA and runs these, however I haven’t really used them because they are a) very loud and b) idle at ~300W each. I don’t feel like the space gain justifies these yet, so I’m still working through my use case and figuring out the best application. Long term I would like one to be located off-site.
* To the right is my first real home server, which is a hand-me-down gaming PC. It’s a Ryzen 1600 with 32gb RAM and 2x8TB drives + 2x12TB drives (two VDEVs, one pool). This hosts my actual TrueNAS and Plex server, but I aim to migrate Plex to the ThinkCentre because I do not like TrueNAS charts.
* Beside that is a CP1500 UPS, also from the VFX studio.
All of this is stacked moderately haphazardly on my LACKRACK.
My house is painfully 90s, so all my networking runs over MoCA 2.5, which works pretty okay, but comes with some limitations, mostly the number of mocha adapters scattered around the house.
This is all very much an ‘in progress’ build, and I have been using building out the ProxMox server as a real education, as this is all hobby, not career related in the slightest.

I think if you look at your local used listings and ebay you should be able to get something that fits the bill. If cost up-front is a concern, then operating cost is also a concern, so you should be considering power draw of the system as well.

I used this spreadsheet to help me choose a recent Lenovo M710 SFF (i5-7500) build I did for pfsense. It’s not perfect, not all mobo pairings are included, but it gives a starting point for power consumption.