The invention relates to an expansion unit for installation in a refrigerant circuit, including an expansion system having an subcooling unit for subcooling a mass flow of a refrigerant that is supplied to the expansion unit, having an expansion/compression unit including an expander stage and a compressor stage, having a branching point that splits off a subcooling mass flow from a total mass flow supplied to the expansion unit and that is connected to a supply conduit that guides the subcooling mass flow to an inlet of the subcooling unit, having an expansion member that expands the subcooling mass flow to a subcooling pressure, having a connection conduit that supplies the subcooling mass flow exiting from the subcooling unit to the compression stage, which for its part compresses the subcooling mass flow to a return high pressure, and having an electrically operated controller that detects an ambient temperature and/or a temperature of the mass flow of refrigerant that is supplied to the expansion unit and/or the expander stage, and in accordance with this temperature adjusts an inlet pressure of the expansion unit or the expansion/compression unit by controlling the subcooling mass flow using the expansion member that is electrically controlled by the controller.