I want to purchase one for my Grey but not sure what size to get. I know what the suggestions are but what would be best if you don't cover the cage at night. My grey can't stand anything covering the front of his cage. I do cover the back and sides. Should I purchase a bigger panel for that reason? We do turn our central heat down at night so I was thinking it may be better to get a large one. My grey is in a cage that is 38.3 L X 38.3 W X 65 H IN
I have a double flight cage and the largest size panel. For that cage (maybe twice your size?), uncovered, the only benefit is if the bird is sitting right by the panel - the heat disappates pretty quickly. I imagine yours would be the same. Covered at night is moderately better, but it isn't going to warm a cage as large as mine. So don't think of it as something that'll necessarily undo turning your central heat down. However, if I attach it to a small travel cage as a 'hospital' cage and partially cover it? It gets nice and toasty in there. Your best bet is probably to get a large one and have it somewhere in the cage that does get covered, since it's partially covered at night - probably near wherever your grey sleeps. That'll give you the best bang for your buck re: heating power and your grey can still sleep near the uncovered part of the cage if it prefers.
All that said, even with an uncovered huge cage, sitting by that panel was my elderly GCC's favorite spot and the younger one break into her hospital cage to sit by it after I removed it from the flight cage. So even if its effects are somewhat limited due to your cage size, your grey will probably still love it.