If you are not the original owner (and maybe even if you are) you probably don't have the window sticker from your car. If you are curious as to what they looked like, here is one. This is from a car that I spotted being auctioned online. The seller posted an image of the sticker so I grabbed it. Unfortunately, the image was of a photocopy. What is most interesting about this is that it seems to indicate that the A/C was dealer installed.
The second one is a better quality example from an automatic this time.