It's the same problem when people propose building giant solar arrays in the desert. Unfortunately, our large population centres tend to be concentrated in coastal areas, and transmission infrastructure isn't free (it's actually super expensive).
EDIT: Just to be clear, I have nothing against renewable energy (I suspect I'm coming off as a little negative here). I just hope that people aren't misled when costs aren't properly factored in (or overstated, in other cases). I actually think there's something rather special about solar PV: it's one of the few forms of electricity generation that isn't just another method of making heat to spin a turbine. Hell, despite its sophistication, fission is just a fancy way of boiling water...
They claim that their solar roof costs less than a traditional roof, and lasts longer. And produces sufficient power for the house.
This approach nicely works around a lot of the very real problems associated with the traditional, more centralized solar generation methodologies.
This to me is one of the biggest issue with solar (and wind) is you need huge amounts of land if you want to really try to replace what is being generated by fossil fuels. Sunlight just doesn't provide all that much energy per square foot. When we stand in the sun on a clear day, we feel comfortable warmth not searing heat.
Do all the cost estimates showing Solar is competitive include the land acquisition costs?