$/W is the only meaningful measure
The primary limiting factor for high PV uptake is cost per W. As the parent says, so what if it is 10x the size, just tile the roof with the stuff.
Of course PV is in itself only part of the equation, It has already got to the state where the inverters etc cost 50% of the cost of a grid connected system. Bringing down cost of the support electronics is going to be the next major issue.
Even if grid connected PV was to provide 100% of daytime power generation, you'd still need power stations to provide dark time electricity. Battery technology is far too primitive to do the job.