Conventional wisdom holds that below $1/W installed cost, it becomes cheaper to do a solar installation than a new fossil fuel installation.
Solyndra have been bragging about breaking the $1/W barrier, but that's $1/W cost to manufacture the panels, on their newest process, for which they're still expanding capacity. That does not position them to sell cells for anywhere near $1/W, though.
What Is Solyndra?s Cost per Watt? -- Seeking Alpha
I haven't seen anything *for sale* for less than about $2.50/W blemished, or $3/W new, by the $10000 pallet.