How many hours of sun per day do swimming pool solar panels need?

That depends on how clean your water is now. Most people run their filter around about 8 hours, however if your water is satisfactorily clean and you are having no particular trouble maintaining free chlorine levels you may be able to reduce it. If you have a salt water pool there is a minimum amount of time that the pool needs to be run in order to produce enough chlorine this depends on the size chlorinator an or pool.