If you are spooling up the A/C be sure it is the only appliance you are running during start up depending on you genny's inrush wattage.
Look on the rating plate of outdoor unit. Find RLA rating...(run loaded amps) and see what that comes to in wattage. Amps X volts = watts. That will give you the running requirements. Remember, this can be higher X's 2 on start up. Have the furnace blower running before you bring the A/C up.
Just remember your A/C can be one of or the highest currant draw in your home.
The "AC" is from the geo unit (Waterfurnace). No separate outside unit.