A method for controlling an uninterruptable power supply arranged between a grid and a variable load, the uninterruptable power supply includes a DC link interconnecting a rectifier connected to the grid via a grid switch, an energy storage and an inverter connected to the load, and a switchable bypass connected between the grid switch and the load and in parallel with the path formed by the rectifier, the DC link and the inverter, the method includes monitoring a power supply of the grid, comparing the power supply to a load requirement of the load, if the power supply meets the load requirement, closing the grid switch, and switching on the bypass, to supply the load with AC current from the grid.