Narrowband Internet of Things (NB-IoT) has been proposed to support deep coverage (in building) and extended geographic coverage of IoT. In this paper, a power control scheme for maximizing energy efficiency (EE) of narrowband physical uplink shared channel (NPUSCH) with the guard band is proposed. First, we form the optimization problem based on the signal model with the interferences of narrowband physical random access channel (NPRACH) which are caused by the non-orthogonality of NPUSCH and NPRACH. Then, a method of reserving guard bands is proposed to reduce these interferences. Based on it, an efficient iterative power control algorithm is derived to solve the optimization problem, which adopts fractional programming. Numerical simulation results show that NPUSCH with the guard band has better performance in EE than that without the guard band.