Hubby has a CPAP also. His is a Resmed brand and he purchased the optional 12 inverter. The machine actually uses 20V DC (same as computers). We are not yet using it as we just got the boat as well and have to wire a 12V plug for it. At home we have one of the portable batteries that are made for running power tools for power outages. It gives him 7 hours of machine time.