This is self-hosting, it is inherently inefficient.

Consolidating servers, storage, power, cooling, networking is always more efficient.

From your example: one full bus is more efficient than any configuration of even the most efficient cars.

I do this for a bunch of reasons, including being a hobby. Hobbies aren't meant to be efficient; first and foremost they are meant to be fun 😊

Dude, chill. This isn't how that works.

I'm pretty chill. I'm not sure attacking someone's efficiency based on their power consumption for an unspecified rack/workload is very chill...

A single Xeon in an R630 with 256GB RAM and redundant PSUs idles around 100W, and that is with no storage controller or other add-in cards, no SSDs or HDDs. Stick some storage, add-in cards and actual load and you could easily see 300W+

Add in a UPS with some conversion losses and some switches, maybe a couple PoE injectors... 600W isn't so far away

Yes we are looking at 2-3 generation old servers, but what do you expect for a home lab? It would be silly to pay a premium for newer equipment solely in the name of efficiency as the costs will far outweigh the energy savings. If you just care about being "green" then your money could do more spent elsewhere.

Sure one can run off old domestic hardware like old laptops/PCs or SBCs like a NUC/RPi but some of us are either trying to replicate a production environment or want/need ECC memory (or both).

Please don't belittle other people's setup just because you might not understand their motivations/constraints or think you might be able to do it "better".

Edit: Not to mention the parent comment said this includes his PC. My PC is a bastion of inefficiency when playing games; have you seen the TDP on current gen CPUs and GPUs?

This is exactly what I do for my personal servers (except with ESXi instead of proxmox).

You will probably want both VMs and containers, there are some things that are not well supported in containers (e.g. gitlab).

I run a couple k8s clusters for work and the complexity is beyond what most people starting out would want, I would imagine.

Unless you need something that has a helm chart but not docker support (e.g. gitlab) or you are really keen on learning, it can be quite a jump...

(For gitlab I still would recommend a VM with the omnibus installer over k8s unless you are big enough to have a separate team managing your k8s clusters. It would suck to have a PV issue and lose all your data.)

I use AMP for hosting Minecraft, Valheim and steam dedicated servers and have been very pleased with it. I did look at Pterodactyl a long time ago but never used it. I think AMP is more advanced, but might be overkill for your needs.