Make sure the genset matches the power needs, which might grow beyond the existing A/C.
Most C's have 3.6/4.0 KW MicroQuiet or Generac equivalent, as in your example. In a B, you will more likely find the 2.4/2.8 KW Onan, because B's usually get smaller air coditioners with lower starting loads, and have fewer 120V circuits and convenience outlets.
For permanent installations my prefence would be the LPG model, since you already buy and store the gas, which does not have the stale fuel problems that come with having more gasoline than one uses in a short period of time. Larger quantities, more frequent turnover help reduce getting stale, but with modern motor fuel formulations this is always something on my mind.
