My search-fu must be weak today because I couldn't find an answer to this question that I'm sure has been asked hundreds of times; what is the best time of day to run ones SWG and pump?

I've been running after sun goes down here around 8:30 p.m., per manufactures instructions I run the SWG for 2 hours and my pump for 4 hours.

Thanks for any help. I've also tagged this for future searches.