That is a very good guess for the fuel consumption! We use a Honda Eu10i generator that have a fuel tank size of 2.1 liter.<p>We (I) fill the generator and start it, and let it charge the batteries until it runs out of gas. 
We start the generator every day now to avoid running the batteries too low.<p>Batteries are 6 x 6 V AGM arranged in 6+6||6+6||6+6.<p>We did consider windpower, but it would have been quite a bit more complicated for our tiny budget. And we would have to have a plan for both days with no wind and days with storm.<p>My dream solution would be a bigger battery bank, and a generator that can start automatically when the battery voltage drops under a certain level. 
Add a huge fuel tank and it would have been able to run unvisited for weeks.