Koldfront PAC 1401W Ultracool
This may not be the finest portable model on today’s market since it has little brand recognition. However, it is the quietest one I was able to find designed for use in a 500 square foot room or small apartment. The audible hum of the fan is a little more that of the compressor, but it is still just as quiet as any you can find today.
In my opinion, even a light sleeper would find it easy to sleep under the sound of this fan. Within just a little while the low, consistent sound becomes part of the white noise that goes unnoticed in the environment.
Although the hoses on this model are a bit bothersome to affix to the window, the cooling is great. On the negative side, this is a heavy unit which may prevent one from moving it between floors.
Honeywell MF08CESWW – Small But Quiet
This model comes equipped with a smaller BTU, but for room sizes of 150 to 200 sq ft it is the quietest. One would not want to choose this one for rooms any larger than that because of its inefficiency to cool bigger spaces.
A tip was shared by one user that could improve the efficiency deficient of this model. Use insulation wrap and tape to insulate the window adapter and hose. Doing so will prevent heat generated by the unit itself from affecting the already-cooled indoor air. The room in which it is positioned will then cool down more quickly with less wasted energy.
It is important to note that this model is quite small and compact taking up little space. However, there is a drawback to its size. When positioned on the floor little cooling takes place above the knee. The good news is that you can put it on a low table to overcome this issue.