The AC system on my unit is really good. Was out for 4 days this summer when the temp was 100 F+ (w/ +70% Humidity) and the Dometic Penguin on top did a great job keeping the RV very cool. Driving, the Ford AC system (factory running off the engine) did a good job keeping us cool too, albeit it's not designed to keep the whole RV cool but actually keep the entire vehicle comfortable. About the only thing you have to get use to is the Penguin can seem loud but we got very use to it and didn't bother us. The other thing I would suggest is getting the driver and passenger door windows slightly tinted because with all those big forward windows...the sun will try to roast you on the drive.