Dometic Fridge - 12V usage

Hi, can anyone advise. Just bought a motorhome and on reading the information booklet it looks like the fridge can only be connected to either gas or hook up to an electric point for it to work when the vehicle is parked up. I used to have a motorhome in New Zealand which worked off the leisure battery when parked up. Do you know if either you can change the wiring system or would you have to connect a solar panel ?