What does a rating of 3.67 (or 4.76, or 2.9) mean?

What does a rating of 3.67 (or 4.76, or 2.9) mean?

The EER of an air conditioner is the ratio derived from dividing the cooling output of a unit (expressed in British thermal units or Btu) with the energy input to the unit in watts.

The higher the rating is, the more efficient the air conditioning unit is. However, a higher rating is usually accompanied by a higher purchase price.