I'd recommend that you don't bother, they're a lot noiser than you might think and they cost a packet to run so expect a decent spike in your electricity bills if you do go for one.
You also need to keep all your windows closed when it's running or you'll end up cooling the street.
My skinflint tip is to buy a desk fan and put a bowl of ice (you can put the whole bowl in the freezer to re-freeze once it melts) in front of it so it blows over the ice. It's surprisingly effective if you get the angle of blow correct…..
it's also a lot cheaper and much quieter…