Hello erky,

When sizing an A/C for a grow room or grow area; a good rule of thumb is to treat the heat from a HID bulb (MH or HPS) as an electric heater.

1/KW per hr is equal to 3,414 BTUs. So 8 lights at 600w each is equal to 4,800watts or 4.8 kw. That gives you 16,387 BTUs to deal with, so a 24,000BTU a/c would be a nice size for your room. It should have enough capacity to cycle on/off and not have to run continuous.

Hope this helps, and good luck growing. :thumbsup: