I'm in the process of getting my Home Assistant environment up and running, and decided to run a test: it turns out that my gaming PC (custom 5800X3D/7900XTX build) uses more power just sitting idle, than both of my storage freezers combined.
Background: In addition to some other things, I bought two "Eightree" brand Zigbee-compatible plugs to see how they fare. One is monitoring the power usage of both freezers on a power strip (don't worry, it's a heavy duty strip meant for this), and the other is measuring the usage of my entire desktop setup (including monitors and the HA server itself, a Lenovo M710q).
After monitoring these for a couple days, I decided that I will shut off my PC unless I'm actively using it. It's not a server, but it does have WOL capability, so if I absolutely need to get into it remotely, it won't be an issue.
Pretty fascinating stuff, and now my wife is completely on board as well; she wants to put a plug on her iMac to see what it draws, as she uses it to hold her cross-stitch files and other things.
7 months later update:
I've expanded HA quite a bit and have a decent grasp on where my electricity is being used. Suspending my desktop has saved a shitload of power: under Linux, when suspended, it draws ~10W of power at any given time vs ~100W when idle. Also, I put smart plugs on the server cluster; the total usage of the entire cluster - 4 mini PCs, 1 SFF, and 5x HDDs (NAS) - over the last 7 months so far is currently at a whopping 465 kWh. That's ~66 kWh a month. Barely 5% of my monthly electrical usage.
What brand are those power strips? Last time I went shopping for power strips, they were all the rage and I could hardly find one WITHOUT that feature. Today, several years later, I can’t find any. Except, perhaps, some Chinese ones without safety approvals. I need one for my tv.
The brand seems to be "Tricklestar" (I have to admit I've never even heard of the brand, but it's been working for years now).