I use the same a/c as the rest of my house! Just blocked off the bathroom vents and sent them to the grow room! now even with 4 1k watt lights in there the room and the rest of the house stay at 70-73 all year long! A lot of people have different day and night temps, not me 70-73 day or night! I know it is bad to go to hot and bad to go to cold but i havent seen proof that the minor temp swing people give them actually helps! (not talking about humidity change just temp)