Power consumption in current communication networks including the access networks is increasing rapidly; energy efficiency is therefore one of the key design considerations in the next generation passive optical networks (PONs). In this paper, we investigate how a wavelength relocation mechanism can reduce power consumption and deployment cost of transceivers in time and wavelength division multiplexed PONs (TWDM-PONs), in which wavelengths and transceivers can be shared among multiple PONs. We analyze how the percentage of deployed wavelengths and transceivers will impact the average available bandwidth and cause extra delay for the working optical network units (ONUs). We show through simulation that under typical ONU online profiles, the percentage of wavelength and transceivers that need to be deployed can be reduced to as low as 30% as compared to conventional PONs, with no resource sharing and wavelength relocation.