The energy efficiency (EE) of an uplink massive multiple-input multiple-output system depends strongly on the number of antennas at base stations (BSs) and the receiver architecture. The existing research has focused on linear receivers, such as those based on zero forcing (ZF) or linear minimum mean squared error detectors. In this letter, we investigate the EE when nonlinear successive-interference cancellation (SIC) receivers are employed at the BSs and provide an asymptotic analysis of the total transmit power with ZF-SIC. We show that to achieve the same spectrum efficiency, the SIC receivers require fewer antennas at BSs, but only moderate increase of the receiver complexity. As a result, the EE with the SIC receivers can be significantly higher than that with linear receivers, as demonstrated by the numerical results.