Electric fans are the most efficient cooling devices. Fans use far less power than air conditioners (see our recent review of the most efficient portable fan). But in hot and humid weather, air conditioning is a great relief. Cooling an entire house uses a lot of energy — it’s much more efficient to only cool the areas where you are sleeping or working, by using a portable air conditioner.

The one of most efficient portable air conditioner we seen is the Newair AC-12000E (pictured above). It has an EER of 14.4. An EER (Energy Efficiency Ratio) of 12 or above is considered very efficient. You can read a detailed explanation of EER ratings here. The Newair AC-12000E is available from Amazon for $389.95

The 7000 BTU Haier HPE07XC6 is one of the least expensive portable air conditioners available.

Reviewers say it does a fine job in very small rooms of about 150-square-feet or less. Since most of the condensed water removed from the air is expelled through the main exhaust hose, you don’t have to empty the water-collection cup too often. The only complaint about this AC unit is that it’s a bit loud, one buyer on Amazon says:

This air conditioner is excellent for the heat of living in the valley near Los Angeles. But it gets really loud, especially when changing over from cool to fan mode ( when it reaches the desired temperature). However, it is not much louder than the multiple fans I had to use before, so I would rate this as excellent.

This air conditioner has an EER of 8.2. It measures just 21″ x 17″ x 34″.

Available from Amazon for $353.