A system and method of controlling inductive power transfer in an inductive power transfer system and a method for designing an inductive power transfer system with power accounting. The method of controlling inductive power transfer including measuring a characteristic of input power, a characteristic of power in the tank circuit, and receiving information from a secondary device. Estimating power consumption based on the measured characteristic of tank circuit power and received information and comparing the measured characteristic of input power, the information from the secondary device, and the estimated power consumption to determine there is an unacceptable power loss. The method for designing an inductive power transfer system with power accounting including changing the distance between a primary side and a secondary side and changing a load of the secondary side. For each distance between the primary side and the secondary side and for each load, measuring a circuit parameter on the primary side in the tank circuit and a circuit parameter on the secondary side during the transfer of contactless energy. The method further including selecting a formula to describe power consumption in the system during the transfer of contactless energy based on coefficients and the circuit parameters, and determining the coefficients using the measured circuit parameters.