COP is also the Coefficient of performance. It is a unit-less measurement of efficiency that represents the amount of cooling (energy displaced) divided by the amount of energy consumed. A higher COP means that a device is more efficient
Example:
A COP of 3 means that for every kw-hr of electricity consumed, 3 kw-hr's of heat are removed from the building (though we seldom think of kw-hrs in terms of heat).