Winter is tough on solar due to low angle and clouds. Cannot say an exact number any more than you can predict the weather. Best shot will be to supplement charging to reduce generator run time.
For travelling I would typically recommend to mount flat on the roof. However for winter in a fixed location a ground set up tilted to the sun is probably best. If you are in a shaded valley or in a bunch of trees it may not even be worth the effort and cost.
Otherwise I recommend 300 to 800 watts and a small 2000w generator. +1 to just start with a utility drop and focus on the project.