I just added one to my cabinet and got it for less than $100 from home depot. It was a 5000 btu. I set it on low and about 2 for my cabinet to stay at 74 with 400W HPS. I do seem to have a humidity spike when it shuts off. I use a heavy duty timer (like for a pool pump, which are $40) and I wired to that so I can run 12/12 with my light. I added a dehumidfier, though it is probably not needed, but I wanted to keep the humd on the money if possible. I had to dump a 50L container after about 3 weeks, so it is doing something.