We have an old HP C7000 at work. It pulls 423W empty, 560W with a single blade. Safe to say it’s a bad idea.

But regarding your question: You already have the thing, so measure it for actual use, as your workloads will most likely vary over time. Or to calculate: E(kWh) = P(W) × t(hr) / 1000, so 3833.025(kWh) = 5250(W)x730.1 The number of hours per month is an average over a year.

Network stack: UDM-Pro, USW-Agg, USW-16-PoE, Raspberry Pi for DNS, VPN & monitoring, U-LTE-Pro, USW-Flex, G4-Bullet, 2x UAP-AC-Mesh, 2x UAP-AC-LR, 1x UAP-FlexHD sitting on a 500 VA UPS pulling ~100W.

Homeserver (24/7) is a Ryzen 3700X-system with 13 HDDs usually pulling around 150W on it’s 1000VA UPS.

Power is quite expensive here in Germany, but the cost of small solar-setups is dropping, so I might setup a little PV-installation to offload costs. Would probably allow me to run more servers again^^

Older now, but interest in computers developed at ~11y/o after not having access earlier, at 13 I was running a Minecraft server for my school. Linux at 14, web hosting with 15, went into IT professionally at 16. Bought my first server for home use at 17. Always kinda just spiraled more out of (my parents) control, I guess^^

TL;DR: Gaming, especially Minecraft.