I almost certainly don't save any money considering electricity cost. I have a dell r630 for compute and an r730xd that I use as a NAS. Then I have one switch for the rack and a POE switch for the house. Probably 3-5amps total?
If I started over, I would probably choose more efficient gear.
That said, I don't mind paying for the electricity too much. I enjoy the warm fuzzies of knowing my data lives under my roof.
A raspberry pi draws 2+ amps. Your dual Xeon server is drawing a lot more power. That said, typically you’d want to measure in watts because amps is relative. Eg a RPI is 2A at 5V while a computer is probably 5A at 120V - an order of magnitude more total energy consumed.
I have some automation that does a weekly archive of everything important to a ZFS-based NAS. Home directories are also stored there over NFS, with hourly/weekly/monthly snapshots.
Once a month or so, I plug in two separate 5TB external HDDs and run a backup script that rsync's everything to each one (2 is 1 and 1 is none). These are stored outside my home.
I should probably get some kind of cloud-based / encrypted backup thing going as well. I don't claim that my current backup system is very good.
Backing up 100+ gigs of data to Backblaze B2 is PAINFULLY slow. I tried to back up a few terabytes and gave up after a few gigabytes because it was so extremely throttled (paid plan) that a backup would have taken weeks or months to complete. (I have gigabit fiber optic service).
If I started over, I would probably choose more efficient gear.
That said, I don't mind paying for the electricity too much. I enjoy the warm fuzzies of knowing my data lives under my roof.