In this paper, the authors consider Orthogonal Frequency Division Multiple Access (OFDMA) systems with simultaneous wireless information and power transfer. They study the resource allocation algorithm design for maximization of the energy efficiency of data transmission (bits/Joule delivered to the receivers). In particular, they focus on power splitting hybrid receivers which are able to split the received signals into two power streams for concurrent information decoding and energy harvesting. Two scenarios are investigated considering different power splitting abilities of the receivers. In that, they assume receivers which can split the received power into a continuous set of power streams with arbitrary power splitting ratios.