Have had a 6.5 kW DC system for 2 years. 28 x Sharp 235W mono panels, with 14 x Enphase D380 micro-inverters.
Using PG&E E-6, this system covers 85% of the electric bill for my very large house, 4700 sq ft, 4BR, 4.5 BA, with hot tub, sauna, dual central AC. The cost savings is about $4000/year. Remaining costs are about $700/year.
I am having another 12 panels installed, hopefully should be done tomorrow. Those are cheap Talesun 240W poly , with Enphase M190 micro-inverters.
This will bring the total to 9.46 kW DC . With the increased size, it is expected to cover 93% of the usage, and 96% of the bill. The only charges that would remain will be the meter charges and taxes of about $155/year. There would be about a negative $300 "true-up" at the end of the year, ie. a dollar credit that would be lost at the end of the year.
This will leave some room for charging a car about 5.5 kWh / day - more than that and there would be positive some electric charges on the true-up.
I would expect about 11 kWh/day usage if and when I get a leaf. If I charge at work half the time for free, this would mean net "free" charging.