In this work, we investigate the energy efficiency (EE) of future wireless communications systems. We argue that operating at high bandwidth and a comparatively low signal-to-noise ratio (SNR) is beneficial in terms of EE. Furthermore, we discuss how employing single-carrier modulations combined with 1-bit quantization and temporal oversampling at the receiver enables energy-efficient wideband wireless communications systems. Our main contribution is to compare the EE of such a system to an idealized conventional system under various assumptions on the ADC power consumption. Our numerical results suggest that the EE can be improved significantly by employing 1-bit quantization and oversampling at the receiver at the cost of increased bandwidth.