Each air conditioner's overall score is made up of cooling performance (40%), energy efficiency (30%) and ease of use (30%).

Our test is performed by an accredited laboratory. Portable air conditioners are tested in a 4.5m x 4m room with a 2.4m insulated ceiling.

Based on power used vs the temperature drop achieved in our test. Portable air conditioners don't currently have energy star-rating labels and can't be compared to split systems. The higher the score, the more energy efficient the air conditioner is compared with others on test.

Testers look at stability, portability, installing the window kit, removing and refitting the air filter, water drainage, controls (including remote controls) and instruction manuals.

This is is the average power consumed in one hour during the cooling tests.

These results are comparative only and measured in dBA raw figures with a descriptive; what you actually hear depends on the environment.

We recommend currently available models scoring 70% or above.

Recommended or typical retail, as of October 2018.

Approximate cost of operating the unit at maximum capacity for four hours per day for three months in hot weather, based on 30c/kWh.

Not all systems have a heating function.

These units are not designed to be carried. They come with wheels for transporting from room to room.

The power cord should be long enough to let the unit reach the window. Extension cables are not recommended as they may overload.

The hose that directs air from the unit to the window.

The maximum length of the filler panel that attaches to the window.

Automatic or "smart" mode means they can be set for a target temperature and will switch to cooling mode (or heating for reverse-cycle models) as required.

In this mode, the air conditioner temperature may increase one or two degrees to aid comfort.

Models with automatically swinging vents, whether horizontal or vertical, may help aid dispersing air around a room.