Just been to price a solar thermal system the customer already has solar PV usal story high pressure sales spiel, he calculated how much they would produce, what they would earn with fits etc he didn't even look at the roof and assumed it was south facing when the installation team arrived it turns out the roof is east facing with shading issues they installed 3 extra panels at no cost but how can they sell a system and estimate its output without checking the roof ffs!.