... our needs will be 4000 watts per day with 6.5 hrs of sun avg..
That
average might bite you.
Take a look at a
solar insolation calculator for where you live. Let's use an example for sunny Centennial Colorado where I used to live with the panels tilted for optimum yearly performance.
Jan | Feb | Mar | Apr | May | Jun |
4.26 | 4.84 | 5.57 | 5.61 | 5.80 | 5.90 |
Jul | Aug | Sep | Oct | Nov | Dec |
5.71 | 5.59 | 5.87 | 5.59 | 4.51 | 4.11 |
"Insolation" is the equivalent amount of 100% power you get on a clear day over the course of a day. Typically you only get 100% power around solar noon for 20 minutes, 80% at 10 am and so on... an insolation number gives you an easy way to figure the maximum amount of power you could get over the course of the day.
In the OP you said you wanted 4 kW over 6.5 hours, or 4x6.5= 24 kWh/day. I saw the other posts where they assumed you were using 4 kWh/d, but a 4 kW generator makes me think you want more and 24 kWh/d isn't much power at all. (A single 60 watt bulb burning all day consumes 1.5 kWh/d).
In December, to get that in Centennial, I would have needed 24 kWh/d / 4.11 h/d = ~6 kW array minimum. That assumes the original 4 kW factored in losses for the battery round trip and inverter losses. The generator is a good idea, but make sure it's power output won't blow the inverter.
If you really only need 4000 wh / day consumption, assuming 90% inverter efficiency and 90% battery round trip that's 4000 / .9 / .9 = 5 kWh, and with an insolation of 4.11 that's 5000 / 4.11 = an array size of 1.2 kW.
What I see on my array is about what the insolation says on average... on rainy days I can see none and on clear days I can see more. So, you'll want to add some buffer to your battery and possibly a couple extra panels.
... prefer to parallel the panels...
On a 6 kW array that won't happen. But, the FAQ has a lot of information for setting up arrays in serial and parallel along with MPPT information.
Hope that helps and good luck!