We have the Truma Aventa rooftop AC and this is the response from Truma direct when I enquired about running it on a Genset...
"You can only change between heating and cooling and so need the 4,2 Amps as maximum current consumption.
Please notice that at the starting of the Aventa there are 20 Amps at the first 150ms needed.
Please use a generator with not less then 2000W and sinus Voltage at the output."
I bought a 2kva Honda at the caravan show last week. Haven't had a chance to test it yet though.
Cheers,
Paul
Edit - Fired up the genie today and it was happily running the rooftop AC and the 150 litre fridge, connected with a 4m 15Amp lead with 2.5mm conductors. One small scare when it ran out of fuel, but I guess they only put a sniff of fuel in them to pre-deliver!