A hybrid inverter generator , comprising: a housing including an outlet through which an AC load can be coupled to the hybrid inverter generator ; fuel cells including a DC power output; an inverter including a DC inverter input coupled to the DC power output, wherein the inverter is arranged to invert DC power received via the DC inverter input to AC power for supply to the AC load when the AC load is coupled to the hybrid inverter generator through the outlet; electrical terminals configured to be coupled with one or more batteries , wherein the electrical terminals are arranged in parallel with the DC power output and the DC inverter input; a controller operable to control the hybrid inverter generator to operate in: a battery-only mode in which the fuel cells does not provide DC power along the DC power output and the one or more batteries provide DC power to the DC inverter input, a battery charging mode in which the one or more batteries receive DC power from the DC power output and the DC inverter input receives DC power from the DC power output, and a boost mode in which the DC inverter input receives DC power from both the one or more batteries and the DC power output; and characterised in that the hybrid inverter generator further comprises one or more battery receptacles for selectively receiving one or more batteries to enable quick insertion and removal of the one or more batteries and wherein the battery receptacles and the one or more batteries have electrical contacts that are coupled when the battery is inserted into the receptacle. a housing including an outlet through which an AC load can be coupled to the hybrid inverter generator ; fuel cells including a DC power output; an inverter including a DC inverter input coupled to the DC power output, wherein the inverter is arranged to invert DC power received via the DC inverter input to AC power for supply to the AC load when the AC load is coupled to the hybrid inverter generator through the outlet; electrical terminals configured to be coupled with one or more batteries , wherein the electrical terminals are arranged in parallel with the DC power output and the DC inverter input; a controller operable to control the hybrid inverter generator to operate in: a battery-only mode in which the fuel cells does not provide DC power along the DC power output and the one or more batteries provide DC power to the DC inverter input, a battery charging mode in which the one or more batteries receive DC power from the DC power output and the DC inverter input receives DC power from the DC power output, and a boost mode in which the DC inverter input receives DC power from both the one or more batteries and the DC power output; and characterised in that the hybrid inverter generator further comprises one or more battery receptacles for selectively receiving one or more batteries to enable quick insertion and removal of the one or more batteries and wherein the battery receptacles and the one or more batteries have electrical contacts that are coupled when the battery is inserted into the receptacle. a battery-only mode in which the fuel cells does not provide DC power along the DC power output and the one or more batteries provide DC power to the DC inverter input, a battery charging mode in which the one or more batteries receive DC power from the DC power output and the DC inverter input receives DC power from the DC power output, and a boost mode in which the DC inverter input receives DC power from both the one or more batteries and the DC power output; and characterised in that the hybrid inverter generator further comprises one or more battery receptacles for selectively receiving one or more batteries to enable quick insertion and removal of the one or more batteries and wherein the battery receptacles and the one or more batteries have electrical contacts that are coupled when the battery is inserted into the receptacle. <EOS>