Solar costs and availability

I recently read an interesting article in IEEE Spectrum, covering the payback time for production costs of solar technology (http://tinyurl.com/2rcpy8). Interesting (and natural when you think about is) is the payback varies by energy intensity. For the Knoxville area, we have (according to the article) 3.0 - 3.9 kwh/sq.m/day. With an estimated 33% efficiency (very high, I know, but do not flame me - it made the math easier), there is 1 - 1.3 kwh/sq.m/day available from a solar system.

I do not have cost data, but wonder if the Nanosolar and other technologies can approach solar cost effectivity for those areas outside California/Arizona/Texas. Some cost analysis is called for (to come).