A method of controlling power delivered to one or more loads in an inductive power transfer (IPT) system includes varying a frequency of a current in a primary conductive path (109), detecting the frequency in a pick-up inductively coupled with the primary conductive path (109), and controlling the power supplied to a load (207) associated with the pickup dependent on the detected frequency of the current in the primary conductive path (109). The frequency of the current is determined by is determined by either or both the load on a power supply (104) of the IPT system or the load on an electricity supply network supplying the power supply (104).