PV Paybacks are long especially if all costs are considered and not what is spent by the agency (subsidies just take money from other investment opportunities with potentially greater paybacks). With that said, if we are going to do it don't do it on roofs. We have enough problems with roofs and installing PV panels on them will probably make them worse. Also roof replacements become very expensive if PV panels must be temporary removed. It would make more sense to obtain vast areas of open fields and install ground mounted and tie these systems into the grid. Though not specifically tied into a particular building for REC credits these can be pooled and shared across agencies. Currently PV Technology is about to have great improvements above the current 17% efficiencies. This would allow for ground mounted systems to be easily upgraded. The issues of what to do with the current PV panels could be part of a block grant program to home owners thus reducing their upfront costs.