definetly it is possible to be off grid, a system built up with 3 x 5 kW or 3 x 10 kW would be sufficient enough to keep loads on a "happy state".
It has to be a combination with a Generator either fuel/diesel or pellet driven system, as in wintertime and in some weeks theres not sufficient sunshine.
A underfloorheating is a "must" to keep a really low temperature heating curve ( easily achievable with 28-35 degrees C only ) by that you have enough energy with a Thermovoltaic and a Photovoltaic system.
Depending on your "Pocketmoney" you either have a bigger batterybank or a bigger Photovoltaic system on your roof.
Also the generator backup can be bigger , once he starts running , heating water and running "Electricity " for free at the same time either batteries get frequently "popped up" or the energy is used to "drive loads" like washing machines or dishwashers.
Of course everything depends on your loads, how effective the system and the costs you have to purchase for.
A normal household will cost roughly 50 000 Euros but can be way less if lights are fitted with Energy saving bulbs and direktly driven via DC / battery supply either 12 or 24 VDC.
So without loads it s difficult to "assume" costs, way cheaper is to run machines with hotwater already supplied.
A combination with a windturbine (if possible) makes also sense. ( I used Marlec from Yachts -very silent and worx with low wind speed already)
ps have fun with this exciting project