I have been using an old PC as NAS and running docker containers (Immich, Nextcloud, paperless-ngx etc.). I got 5 3.5" HDD disks and a Nvme. Even on idle, I am consuming 50-60w. A friend of mine is selling a Qnap NAS which is a dedicated machine and probably consumes less power, although I don’t know if it’s worth it.
Easiest way is to use a tasmota based power plug. They need to calibrated once,but then are pretty reliable and can be found for 15 bucks.
Nous A1T (or similar nous,but watch out for the T at the end, Z is zigbee) is popular in central europe. They are well built and cheap as fuck. But again,they need to be calibrated once which you need a steady user (e.g an old incandescent light bulb ) and a multimeter for… It’s easy and only needs to be done once.
Another option are the Inter-Tech PDUs, they costs around a 100 Bucks, are fully IP, can switch channels but only measure the consumption of the whole strip. If you have a more advanced USV they often have a total power consumption measurement.
If you want to go all in you need to look for “switched and metered” PDUs, but they are fucking expensive. The Cyberpower PDU81005 is the cheapest “good” one and is over 400 bucks here . So… Most people won’t do that,even in a professional setting.