I have a 8.775kW array and have been using it for about two years now. I have 39 SunPower SP225 panels and my system averages about 50kWh/day in the July and August and is down to about 25kWh/day in December and January. Both figures are for nice sunny days. I'm not 100% sure how so use the efficiency rate because there's obviously something amiss in the calculations.
Here is a link to view my solar production in real time. You can also look at past production. As I said, I have 39 panels that are 225 watt each (39 x 225 = 8.775).
I'm driving an ActiveE now and running it on sunshine!
https://www.sunpowermonitor.com/resi...7&type=address