First, determine how much you are able to spend. If your budget is unlimited, then this decision is going to be far easier because there are many AC functions that are currently available and a vast range of qualities in different AC options. So create your budget before getting started and then use this as the basis of your research.
You should next consider the size of the area that you wish to cool down. If you plan on cooling down a larger space, then you are going to need a more expensive and powerful air conditioner than if you were simply trying to keep a small space cool. The size of your room is a vital factor so think about where you will be placing the unit before choosing an option to buy.
Think about Humidity and Heat
You also want to think about the humidity and temperature levels in your area. There are some climates that are quite mild and this make them easy to cool down in with a good AC. Other areas, however, tend to be very sticky and hot and this means that you are going to need a portable air conditioner that is a bit larger and more costly.
Before you start researching different options, make sure to determine you needs as this will help you in your purchasing decision. You should not spend more than necessary, but you should be willing to spend enough to get a model that will do the job right.