Right, I'd written a whole load out for you then lost it when the post disappeared. I'll start again.
There are two types of current we are familiar with in this country.
DC - what solar panels produce
AC - what we have running through the ring mains in our houses.
AC and DC currents can both be fatal. So far as DC is concerned the likelihood of a fatality when shocked often comes down to where the current enters the body and where it leaves. The most likely to be fatal route through the body is in through one hand and out through the other. This way it's most likely to cause a cardiac arrest. If it enters via a hand and leaves through a foot it's less likely to kill but can still.
To help avoid accidents. If you ever feel a shock whilst cleaning solar panels, stop immediately and don't continue. Tell the owner.
You can wear electrical insulation gloves and boots suitable for working in this sort of environment.
http://www.cablejoints.co.uk/upload/Insulating_Boots.pdfhttp://www.cablejoints.co.uk/sub-product-details/insulating-gloves-boots-lv-hvIf possible, although not always easy considering what we do try to keep the working environment dry, electricity loves damp environments.
Work off rubber mats where possible.
That'll be £195.00 plus VAT.