[Sans Peur]

As above only 3 options. Shore power, generator or inverter with a good bank of batteries. You would probably have to put larger alternators on the engines just to keep up with the drain on the battery bank and even then it isn't going to stay ahead of it.

An air conditioner pulls alot of power and with an inverter using house batteries will draw them down quick. Make sure of having separate battery systems for the inverter and engines. Setting at anchor and not being able to power up the engines would suck.