>using an old PC I had and it works great. Don't know why people are so crazy about buying prebuilt NASes.

The problem is the "old pc" is typically a desktop-class cpu which is very power hungry. (~100 watts). And to make things worse, the older cpu has slower performance that doesn't justify the extra watts it consumes.

For 17+ years, I used a 2008 era Intel DX58SO motherboard + Core i7 920 in a full size Silverstone tower case as my NAS. It originally started with 1.5 TB drives and I just kept upgrading the drives all the way up to 16 TB. It worked ok and was reliable so I was never interested in turnkey NAS appliance like Synology, etc. I also wanted to install my own os, plus recycle/reuse/repurpose philosophy, and not be shackled by a proprietary NAS ... yada yada yada. The big problem with re-using my old PC is that at idle, it consumed 125 watts.

Electricity isn't 11 cents per kWh like it was 17 years ago. It's now 21c/kWh -- and will keep going up because of AI, oil prices, etc.

Last month, I did a lot of research to reduce the power usage and ended up buying a UGREEN DXP4800 Pro NAS appliance. UGREEN lets you install your own os and it uses a laptop-class cpu (much better performance specs than Synology) which is much more power efficient. At idle, it consumes just 25 watts. Also, the Intel i3-1315U in the UGREEN has a Geekbench score of 2124 which beats the i7 920 of 450. So 4x the performance while using 1/5th the power usage!

I briefly considered "upgrading" my DX58SO/i7-920 to another old pc (2014 era) X99/i7-5820K. That's slightly more power efficient of ~80 watts idle. However, running ffmpeg to convert videos makes it jump to ~180w! The UGREEN can do the same ffmpeg conversion with better performance and yet it only increases to ~45 watts.

Another unexpected bonus of lower power usage is that my server room temperature is noticeably less warm, and the lower power UGREEN gets 3x the runtime on the APC battery backup when there's a power outage. The UGREEN did cost $700 but the savings on the electricity bill will recover that in about 4 years.

I also like the UGREEN toolless hard drive sleds. The old Silverstone tower hd sleds required screws. I also like the smaller footprint. The NAS appliance was a total quality-of-life improvement.

The only thing I "lost" from the old tower setup was the CD/DVD drive bay. But I don't rip discs anymore so I that doesn't matter. If I really really wanted to, I can hook up a DVD drive to the UGREEN via a SATA-to-USB adapter but I hope to never buy physical media again so I don't expect that will happen.

There's an allure to re-using a "free" old PC as a NAS and there's also the pride of a DIY storage solution. However, that mindset also makes one overlook the negatives of that setup. Sometimes, "free" items actually cost more money.