if it was 40 panels we would charge £100.00 maybe add a little as its so green say another £20.00
you'll be surprised how you can clean off with just pure water, a sil brush and giving it a bloody good soak.Matt
I have found that £5.00 a full-size panel is a good guide. Whenever I have priced less than this I always regret it. Ultimately we should be earning more than we can earn on window cleaning, otherwise it is pointless taking on the work.