I can't remember what the payback was - but it is massive - far far more than 4 or 7 years that has been talked about.
He says it is a crock at present.
I thought the 4 - 7 years was rubbish, but can't prove it. In the 70's I was working on a project using PV cells to power remote radio stations. The engineer remarked that they would NEVER pay back the cost of manufacture if there was an alternative energy source.
