Hi Almot,
"The MSH-M Series combines the energy from both the AC input and the batteries to power the inverter loads. This feature gives the inverter the ability to recharge the battery when there is surplus power, or to deliver more power to the loads if they require more than the AC input can supply by itself."
Since the OP is in a truck camper he:
A. is forced into at most a four battery set up
B. has limited roof real estate for solar
C. this inverter will play well with a smaller generator, allowing a 2000 watt unit to run the air conditioner.
Almot wrote:
Don, those are interesting hybrid inverters by Magnum. I only think that they supplement from the battery bank not necessarily during high demand, but rather when there is AC power failure, i.e. "blackout", or AC voltage drops too low. Could be during high demand (i.e. from all the users) on the grid, yes. If you wish to switch to the bank, for example, when you're not running airconditioner and there is no 120V failure or blackout, you have to switch it manually.