http://thefraserdomain.typepad.com/energy/2007/04/new_engine_desi.html#comment-65446216

Yep if 15 cents per kwh could be reached by solar roof top application, it would take off. Especially with 10 cents in subsidies per kwh.

I think it's feasible in a turnkey installation with mass production and installation. But the design would need to be trough concentrating PV (at least 10 suns, 39% efficient)with heating/cooling capacity cogeneration. But the heating/cooling savings would need to be taken into account.

It would need to be installable like metal roofing with plugin features to standard electrical home/grid technology and standard water and home heating/cooling technology.

It would be cheaper in sunnier climes. But that average of 15 cents per kwh would do it. It might cost 5 cents per kwh in the desert (where standard air conditioning costs are astronomical)and 20 cents per kwh or more in very cloudy, temperate regions, like Seattle.