Provide those "studies" including specific properties with and without solar to the appraiser and he'll tell you if theres a difference in market value or not.
What about properties with 'purified' water even in the toilet? should those sell for more than those without purified water?
This study shows that Homes with solar sold 20% faster and at 17% more than comparable homes without solar in California.
http://cleantechnica.com/2010/10/23/solar-homes-sold-20-faster-and-for-17-more-nrel-study-finds/
A purified water system does not really compare because it provides no payback to the consumer. It may be something some people want, but solar can put money back in your pocket right away.
Simply; They look ugly.
So you're saying your figures are accurate for all different systems, panels, inverters, installation providers and areas of the country?
Sorry, but I have a local solar company giving me entirely different reliability and performance numbers and nowhere near as optimistic as yours.
Spartacus,
There may also be some obsolescence issues inherent as the technology is still evolving and advancing and the typical buyer for this system wants something cutting edge and is not concerned in buying the 5 year old system. I will also tell you that if it were really and truly beneficial and that the total upfront costs were greatly outweighed by the potential savings, everyone would have one.