I was quoted $.59 on January 11th, 2013 – I” likely see $.50 by year end.

I’d expect to see $.25 in 2017, especially if 1366 Technologies unleashes by then.

In many areas, it's cost competitive today. In other areas, it's not yet there. As GreenPlease says, there are a lot of other costs besides panels, much of them are not parts at all, but permits and so, for example, it costs 2x as much per watt to install residential solar in the U.S. as it does in Germany — using the same equipment!

When the panels are 50 cents/watt, there's a near certainty that solar will compete on a kw/hour basis in the bulk of the world.

Now, that said, solar only makes power a portion of the day, so it can still only solve a part of the power equation for the time being.

First, the article above refers to the cell price. At $0.50/watt for cells, you might be looking at $1.10-1.25 including the balance of system (inverter, wiring, racking, installation). To get the cost per kwh, one calculates the number of hours of sun exposure over the system’s life multiplied by the capacity factor (insolation above/below the standard 1,000w/h/m^2). Divide the resulting number by 1,000 to get total kw/h produced for the system’s life. Divide the cost by this amount.

For example, at $1.25/watt installed, assuming 1,000w/h/m^2, 6hrs/day of sun (I’m adujusting for the distribution of sunlight throughout the day… weak at dawn, strong at noon, weak at dusk…. and approximating), and a 20 year life:

$1.25/[(1x365x20x6)/1,000]= $0.028 or 2.8 cents per kwh.

That’s not entirely accurate as you have to include the costs of financing. Say you pay 5% over 20 years for you financing. Off the top of my head, that $1.25 turns into ~$3.20 so your cost would be ~$0.068 or 6.8 cents per kilowatt hour.