A/C Unit for Small Grow room, Suggestions?

I have a small closet grow room, temps getting pretty high, I'm ok for right now but when it starts to get warmer outside I will deffinetly need to think about either not having this grow room, or somehow cooling it down.
I am on the 6th day of my first veg right now, I am going to wait for my first harvest to make any major changes or purchases, but I would like to know what other ppl use for a small A/C unit in their small grow room. Its 2 feet by 7feet, and about 8 feet high.
I do not have a window in the room, my exhaust fan is in my bedroom window a few feet away from the closet, with duct tubing directing the tube into the room, so I dont have a want to put an AC unit in a window.
Do A/C units cost a lot on my electricity compared to my 600w HPS light?

I have a portable ac unit in my 5x5 grow closet, i cut a hole into the cieling to vent the hot air that comes out of the a/c works great.........but you have a small grow space and a/c like mine cost a min of 300$ but the window units costs less

The money that you spend on electricity should be dwarfed by the amount of herb you are pulling down. Any $100 A/C unit would be good enough to cool a 600w. You'll want about 5,000 - 6,000 Btu for that $100 A/C. If it get's really hot in the summer you'll want to think about an air-cooled reflector.