I thought this guide would be of use to anyone purchasing a portable air conditioning unit for use in the home as I have experienced many different models and types.
There are basically two types of portable units - the single unit (which has a vent hose to outside like a tumble dryer pipe) and the split type (two units connected by a thick cable). Both of these are refrigerated units which produce cold and dehumidified air.
The single unit type is very easy to install, you simply position the unit and put the hose out through an open window or door, or alternatively through a vent fitted through a wall. These are ideal for temporary use and easy to move but in my experience are too noisy to use in a bedroom. On some models you need to empty the condensation water from a tank inside, this limits how long it can be used for before it stops with a full tank. The quietest models are DeLonghi, Carrier and Toshiba.
The split type of unit has two units (indoor and outdoor) connected by a refrigerant line. These are normally more powerful and suitable for larger rooms but being in two parts and larger are less portable. On most units the connecting cables/pipes can be undone to allow the pipe to pass through a small hole in a wall etc. before being reconnected, this is fitted with special Aeroquip connectors so that the refrigerant does not leak out when undone. The outdoor unit can be fitted on a wall or used freestanding. I have installed one of these by cutting a slot in a window frame rather than having a hole through a wall. This type of unit is by far the quietest and most energy efficient of all portable units. Unlike the single units which tend to waste some of the cold air as the hot air going out of the exhaust sucks air out of the room, these recycle room air and so work much better in windy and very humid conditions. They can also run continuously as the condensation water is pumped away to the outdoor unit (no emptying needed). In my experience DeLonghi are the quietest and most reliable.
To effectively cool a room, the unit must have a cooling output (btu) that is enough for the area covered. As a rough guide, take the size of the room in feet, multiply length by width by height times five to give required btu output, then choose a unit with at least this output.
Note that there are also air coolers that work by evaporating water added as the air blows through the unit, these can be useful in large open areas and/or hot dry conditions but are no good for humid weather or use in small rooms.