This letter proposes a power-efficient full-duplex (FD) self-backhauling scheme for small base station (SBS) downlink cellular networks. To this end, unlike the access link where the UEs’ downlink packets are forwarded through individual subbands (SBs), the multiple UEs’ packets in the backhaul link are formatted into a single packet having a wide bandwidth. As the access link transmit (TX) power levels differ, SB by SB, each SB in the backhaul link undergoes different power levels of self-interference from the access link. Hence, backhaul link TX powers for multiple SBs are jointly optimized group-wise so total power is minimized while maintaining the same capacity as a conventional UE-wise backhaul scheme. Nominal system parameter settings achieve backhaul link power savings of more than 3 dB, and the power-saving gain even increases as the target SINR decreases or the UE grouping size increases. If additional channel gain factors (such as shadow fading) are considered, the power saving gain is further enhanced.