It depends if your boat has a power point that is not backed up by the inverter. If you have one, you can plug iSocket to it, and that way you will know that shore power is lost because that power outlet will lose power. If you plug the iSocket into an outlet after the inverter (backup power), you will probably also be notified of both a power outage and a power restoration, depending on how quickly your inverter reacts to a shore power loss (if not faster than 1 sec. then it should be fine to receive both messages). In this way, you will be in control of both shore power failure and inverter operation.