Kimblbob,  Despite the HBA not being used, it will be utilizing resources. Now granted this is a very miniscule amount, but it does use them irregardless. When the card is installed it will draw power, as well as the host server will spend processes in sending "heartbeat" communications with the card, so that it is prepared to use it.. So while it is a VERY small amount, it does use them. I don't see any issue with you removing it during a maintenance window.  Hope this helps answer your question.
We have a Dell Poweredge R720 server that has an orphaned Qlogic host bus adapter in it. The lights on the HBA are flashing yellow, green, and orange. I am wondering if this orphaned adapter could be using system resources and if it should be removed.
Should fiber channel host bus adapters be removed if not in use?