Solar Energy’s Exponential Model?

So I watched this video by Ray Kurzweil:

http://www.ted.com/talks/ray_kurzweil_announces_singularity_university.html

At 5:38 he shows a graph of Photovoltaic Production. The graph shows an approximate doubling of photovoltaic use every two years.

I thought this was interesting. I’m sure cost was a factor in this behavior. What would happen if you graphed the cost of solar power per kW. Perhaps the cost of solar power is also following some sort of exponential model, and we can see when the cost of solar could rival the cost of coal/oil/other forms of energy.

Does anyone know if this has already been done? Does anyone know where I could find historic prices (like cost of solar/kW)?
Although, I wasn’t able to find the average cost of solar per kW, I did find a site with a lot of solar data. Look under energy at www.swivel.com.

The present selling cost of solar Panel is about 3 US $ per watt.So per KW it is costing 3000 $. This cost of investment is very high in terms of return gain by using the solar energy compared with fuel used electricity. Unless we found some method to reduce the cost of production of solar Panel to one third of present cost it is not an alternative.