> I just set up a test server with a J1900 (10W TDP.) With 8GB RAM and running from an SSD it uses 25W.

Did you use a regular desktop power supply? PC power supplies can consume 10-15W or more at idle. To build a low power system you need to find a good low power, high efficiency power supply.

Does anyone know a good supplier for such supplies?

For 10 years my home server used a Corsair VS350; it was fantastic, and very efficient at low power draw. Recently the fan failed. The PSU seems discontinued. The _fan_ seems discontinued. I'm going to try replacing the fan but I don't know much about electronics. As a temporary measure, I got a regular "gaming PC" PSU and it has 10% more power draw, it's not efficient at all.

I've been looking for a replacement PSU, and I can only really find very high power ones - minimum about 550W - for reasonable prices. While you can run a low wattage PC on such PSUs, none of them make very much in the way of efficiency promises; only the highest certification, 80 Plus Titanium, makes efficiency promises for 10% load, e.g. it'll be 90% efficient for a 55W load on a 550W supply. Lower certifications only promise to be e.g. 80% efficient for a 110W load on a 550W supply, and make no promises at all about a 55W or 30W load.

So, how does one buy a good low power, high efficiency PSU, without it costing a fortune?

> I'm going to try replacing the fan but I don't know much about electronics.

Just in case: opening PSUs is dangerous without precautions. The capacitors may retain enough charge to kill.

Besides the immediate risk to yourself, a PSU can also pose a fire hazard during operation, e.g. if improperly cooled.

This was measured with an old school Kill-a-Watt. When idle, the HDDs spin down. Keep in mind these are 2.5” likely 5400rpm or less (WD Passport 2TB).

2.5" hard disks actually use way less power than the 3.5" drives, but if you spin down the bigger drives they get down to about 1watt.

My server at home I actually use a 2.5" drive for the torrent scratch disk since I don't really need speed there I just need something that is always spun up with a moderate amount of space that doesn't use much power.

Running powertop --auto-tune and TLP makes a lot of difference on my server (60->30W). You can further tune CPU, disks and GPU to preserve energy. I suggest starting with a laptop or a phone (~postmarketos)instea d,as those are already tuned for low-energy modes, and you won't have, say, a BIOS preventing PCI devices from sleeping (looks at server).

UPS’ also have this feature and it’s interesting to see the idle vs load wattage.

I like the idea of making compute, storage into appliances if possible locally.

It’s best to use ssds in the machines.

If you want spinning drives put them in a dedicated nas for storage.