The info on the box is not that reliable IMO. A Champion 3100 successfully powers a 14.8k BTU Whirlpool window a/c unit in my garage--even in 108 deg heat.
There are no guarantees, but I would be surprised if your Champion 3100 did not power your a/c. A Champion 3100 powers my roof-top Dometic 13.5k BTU a/c (which does not have start cap) just fine.
FWIW, if your Champion 3100 is operating properly, and is unable to start your a/c, then a pair of paralleled Honda EU2000i's or EU3000iS have even *less* of a chance of doing so. The Champion 3100 is capable of producing more inrush current then both of these Honda configurations.
