It bears repeating.
Never buy a house because it contains a solar panel on the roof. It is DEGRADED.
I’m not talking about residential solar but rather big utility scale solar. If you fly over the southwest you can see these gleaming circles of reflected sunlight dotting the landscape these days.
US subsidized utility scale solar in the desert southwest runs about .04@kwh —as of 2015.
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NV Energy recently reported signing a PPA for the 100 MW output of First Solars Playa Solar 2 installation at $0.0387/kWh after paying at $0.046/kWh for the output of SunPowers 100 MW Boulder Solar installation last year. The utility bought utility-scale solar power for an average of $0.1377 per kWh for solar generation over the course of 2014.
Austin Energy recently received record low bids below $0.04/kWh in response to its 2015 request for proposals (RFP). Those bids were 20% lower than the contract it signed with Recurrent Energy in 2014 for $0.045/kWh and only 25% of the $0.16/kWh it paid for the 30 MW Webberville project, the utility’s first large installation.
You seem to be laboring under the idea that said solar panels are not outputting power. A quick check online shows that the degradation of panels is from 100% to 75% over twenty-five years, not to zero watts.