Yeah server hardware isn’t the most efficient if you want to save power. It’s probably better to get a NUC or something.
With that said my old Dell PowerEdge R730 only uses around 84 watt (running around 5 VMs that are doing pretty much nothing) The server runs Proxmox and has 128 GB of ram, two Xeon E5-2667 v4 CPUs, 4 old used 1 TB HDDs I bought for cheap, and 4 old used 128 GB SATA SSDs I also bought for cheap (all storage is 2,5 drives).
All I had to do was change a few BIOS settings to prioritize efficiency over performance. 84 watts is obviously still not great but it’s not that bad.
The only reason that I have measured my server is that it has that feature built into the iDRAC. I have been thinking of buying an external power meter for years but have never bothered to do that.
Luckily I got my server for free from work. It was part of an old SAN so it came with 4 dual 16 Gbit fiber channel cards and 2 dual 10 gigabit ethernet cards. Before I took those out of the server it consumed around 150 watts at idle which is crazy.