PoE actually saved me, or at least helped me simplify some things. My router is in one place, while the distribution box where all the cable conduits lead to every room in another place. The distribution box (where also the optical cable originally comes from to the router) has no power plugs. I wanted to have Ethernet plugs in every room (especially for any fixed devices), so I managed to find (quite difficult in Germany) a PoE powered switch for the distribution box with no plugs available, get a PoE injector to power it and from there on to wire and install Ethernet plugs in all rooms.