The invention relates to energy saving in vacuum systems by means of a method and a controller enabling to consider the fluctuation in system-pressure of a system by determining a maximum system-pressure S2H and a minimum system-pressure S2h for each working cycle WC based on a determined target system-pressure pn− and a pre-set system-pressure p0− for the current working cycle WCn (n=1, 2, 3, . . . ). The method is especially adapted to fluctuations in system-pressure level of a vacuum system comprising a vacuum gripper tool.