Our favorite windowless unit is the Whynter 14,000 BTU Dual Hose Portable Air Conditioner (ARC-14S). You really cannot go wrong with this unit. It comes at fair price and provides excellent cooling. You can even find models of the Whynter that come with heat for year-round use.
The weather can become quite severe during the summer. Some days you might find that you are cold while in the house and need to cut the heater on, while on others, you will be uncomfortably hot and given that you have no AC, there will be nothing that you can do save shedding a few layers of clothing and opening the windows.
This is why a windowless air conditioner unit can be so beneficial. Not only can you use these throughout the daytime, but you can also use them at night when you feel too sticky and hot to get to sleep. Air conditioning units can keep you cool and will make the air around you more comfortable so that you can rest easy.
There are numerous options in windowless AC models and some of these are fairly small in size while others are much larger and require more space. This is definitely something that you should consider.
It can be helpful to have this unit out during the summertime, but what should you do during the winter? You will have a large unit that must be stored. This is one way in which models differ.
It may be possible to get a windowless option that is built on wheels or casters that make it easier for you to move this equipment around and to find a feasible place for storing it.
It is possible, however, to find smaller designs that will save more space when in use and when it is time to store the unit. The attic is one place where you can store these, but attic storage will likely prove problematic if you buy a large, heavy model.
One other thing to consider is the amount of noise that a model produces. If you plan on using this system for nighttime cooling and to help you rest better, you have to consider the level of noise that this equipment is going to produce. Some options are very quiet when operating and you can hardly hear them. Others, which are usually lower in cost, tend to be much louder and thus, even though these can cool you down they may be too noisy for you to get good rest.
Additionally, when these systems require maintenance such as draining, they might make beeping sounds. Should this happen at nighttime it can wake you. Is this what you are looking for? You have to evaluate and test each of the features that a model provides before investing. It is always a good idea to read small windowless air conditioner reviews as well.