In order to keep my eletricity bill for a running system in my apartment to then minimum I researched the specs & prices from the "The Power Consumption Database"[1] and found an intel nuc running on 5watts idle. Thats the same class of power consumption of a raspi 4 8GB, but easier to maintain. Now I'm waiting for my a Coral TPU USB-Accelarator to keep the peak consumption down for some recognition tasks in homeassistant.

[1]http://www.tpcdb.com/list.php?type=13