This is a pretty awesome project, and is very well done! I’d love to see more pictures!
It looks like custom PCBs for the blades and the backplane? More details on that would be very interesting.
What all are you running on this system so far, and what software do you have plans to add? Are they running independently or as a cluster?
Summoning u/geerlingguy here, I’m sure he’ll love this project!
Wifi is fine for some things, but it’s power hungry, it requires an IP address for each device, and is subject to interference from other wifi devices. If you want to block all of the devices from accessing the internet, it adds some extra complexity. If you have a battery powered wifi device, it will power itself off until activated, then have to connect to your wireless network (DHCP, etc) before it can transmit, which takes a second or three.
ZigBee, ZWave, and BLE are low power protocols, and are fairly statically configured. They use less power and can have much better battery life on much smaller batteries. When activated, they connect back to their respective networks immediately, so things like smart buttons and motion sensors are very fast.
What about using a Shelly relay with power monitoring, and installing it inside the outlet?
I have a few Shelly 1PM Pluses that I do this with, but Shelly is starting to make ZigBee and ZWave devices too. I haven’t looked to see if they have a ZigBee one with power monitoring, but I’d bet they do.
Another option is something like using an Emporia Vue 2 or a system from Circuit Setup to monitor power from your breaker panel. Both can be flashed with ESPHome and record directly to HA. Not sure how well they work in the EU, but I’m planning on getting an Emporia Vue 2 here in the US.
I voted DIY - No regrets. Myself (and a lot of others here) run used/surplus enterprise hardware that’s cheap/free. You’re kind of missing an option for that.
My primary NAS is a PowerEdge T620 with 13x 8TB HDDs (8 in the built in drive cages, 5 more in a caddy that fits in the 3x 5.25" bays). The server and the drives were free/surplus, but I bought an upgraded pair of CPUs (E5-2695 v2’s) , 128GB of RAM, and the drive caddy, for probably $200 total. It’s getting a little long in the tooth and I’ll be keeping my eye out for something newer (and less power hungry) during the next round of decommissioning.
This scratches my ‘play with enterprise hardware’ itch and is easier on the wallet upfront, but the power cost is probably more in the long run.
Also, you’ll likely get very different answers in the polls here vs in r/synology or similar. You’re asking homelabbers here, so you’re going to get homelab answers. But that’s okay, because it sounds like you fit in just fine here!