My heat pump / air handler is about 25 feet from my audio system in an enclosed room that is well sonically insulated. I also have a variable speed air handler and pump so, is if the house is only slightly warm… it is on very low and barely running.it is not at all obvious it is running.
That said, when running at all it increases the ambient background noise from the high 20db range to the mid-thirties… and negatively effects listening. What is amazing is that it does not just effect really quiet passages… it effects all but really loud ones. I am not hearing any electrical effects, just the increase in the background noise level.
My air conditioning system can be remotely controlled on my iPhone. So, I will temporarily turn it off while listening. Or even pre-cool a bit before a listening session.