What are people’s opinions on covering their A/C units during the winter? I’ve noticed about 25% of my neighbors have covers over their A/C units. I’m talking about the external big metal box sitting on a conrete slab in the back or side of you house type of a unit. An HVAC professional I asked said the covers were a bad idea because the units are constructed to withstand winter conditions and the cover will keep moisture in and cause premature rusting.