The panels produce DC voltage/current. The voltage depends on the panel and how many cells are wired in series. Inverters can be very efficient. Typically around the 96% range. Maintenance on the inverter should be low if designed properly. They have no moving parts other than perhaps a fan and some relays.
http://www.solarelectricalsystems.com/documents/kyocera-kd135gx-lp.pdf
The above panel (a quick Google search) has an area of about 1 meter squared (10.89 square feet) and produces 95W with 800W/m^2 of sunlight. So with 20 8 x 10 panels worth of area (1600 square feet) that would produce just under 14kW with typical direct sun light. To convert that to AC using a 96% efficient inverter the inverter would output about 13.4kW. And yes their are other losses, but you'd have to lose another 10% to get to 12kW AC. You don't need batteries if you don't go off grid.
A typical house can nearly zero out its electricity usage for about $40k of solar equipment. But that's only because of all the subsidies and tax giveaways. Typically those subsidies and tax giveaways amount to about 30% of the cost of the project...
Without those subsidies and tax giveaways the economics of it is very debatable.
Your calculations may seem good to you, but do not reflect reality, IMHO. The panels almost NEVER realize their full capacity, and begin degrading as soon as installed. Dust (and anything else) accumulations also take their toll.
...Example: in 2009, Germany’s actual national PV solar CF was 6,578 GWh/(7,890 MW x 8,760 hr/yr) = 0.095 out of a national theoretical maximum of 0.115. The actual CF indicates the PV solar panels are aging, dusty, partially shaded by trees, partially snow-covered, roofs are not be true-south-facing and the panels are not correctly angled; about 80% of the PV solar systems are roof-mounted. Germany could raise its average CF, if it installed more field-mounted suntracking PV systems that would have CFs of about 0.16 - http://bifuel.net/starter-homes-get-solar-panels-as-standard-equipment/
The rated capacity is at noon, in full sunlight, and that MAY only happen once each day... and anything less....is less! I hope your air conditioning doesn't draw many AMPS!
The biggest fraud currently (other than the pResident) is the guy on TV talking about a "solar generator" for times when your power goes out. "Just hook it up in the middle of the storm..."
http://www.mysolarbackup.com/?gclid=COPIxcjtuagCFQXu7QodA3wqCA
