In a method for performing a balance check with an elevator, a power model of the elevator is established, including the motor power fed to the motor (PM) and power parameters of the motor and the moved components in the hoistway (PK, PP, PFr, PCu, PFe), a test run of the elevator is made, mid motor power values for the up and down direction are determined, i.e. the power fed to the motor at the instant when the car is moving through the middle of the travelling path of the elevator in up and down direction with constant velocity, the difference between the mid power value in up and down direction is determined, the balancing weight difference is obtained from said mid power value difference. This method allows an easy determination of the elevator balance preferably in course of modernizations of an elevator system with a new elevator motor.