The paper analyzes the energy efficiency and spectral efficiency of very large multiuser MIMO systems, where a base station (BS) with a large number of antennas serves multiple single-antenna users. The BS uses imperfect channel-state information (CSI) derived from transmitted pilots to separate individual data streams. The paper derives lower bounds on the achievable rates for maximum-ratio combining (MRC), zero-forcing (ZF), and minimum mean-square error (MMSE) receivers under both perfect and imperfect CSI. It shows that with perfect CSI, the transmitted power can be reduced proportionally to \(1/M\) if the number of BS antennas \(M\) grows without bound, while with imperfect CSI, the power can be reduced proportionally to \(1/\sqrt{M}\). The paper also quantifies the tradeoff between energy efficiency and spectral efficiency, demonstrating that in the low transmit power regime, both can be simultaneously increased. Additionally, it shows that very high spectral efficiency can be achieved with simple MRC processing, even with imperfect CSI, and that this can be achieved with orders of magnitude reduction in transmitted power. The analysis is extended to multicell systems, where the power-scaling law holds and residual inter-cell interference remains.The paper analyzes the energy efficiency and spectral efficiency of very large multiuser MIMO systems, where a base station (BS) with a large number of antennas serves multiple single-antenna users. The BS uses imperfect channel-state information (CSI) derived from transmitted pilots to separate individual data streams. The paper derives lower bounds on the achievable rates for maximum-ratio combining (MRC), zero-forcing (ZF), and minimum mean-square error (MMSE) receivers under both perfect and imperfect CSI. It shows that with perfect CSI, the transmitted power can be reduced proportionally to \(1/M\) if the number of BS antennas \(M\) grows without bound, while with imperfect CSI, the power can be reduced proportionally to \(1/\sqrt{M}\). The paper also quantifies the tradeoff between energy efficiency and spectral efficiency, demonstrating that in the low transmit power regime, both can be simultaneously increased. Additionally, it shows that very high spectral efficiency can be achieved with simple MRC processing, even with imperfect CSI, and that this can be achieved with orders of magnitude reduction in transmitted power. The analysis is extended to multicell systems, where the power-scaling law holds and residual inter-cell interference remains.