We study energy-efficient power allocation for the sensing-based spectrum sharing (SBSS) of the cognitive users operating in an uplink multiuser MIMO mode. Different from the existing energy-efficient designs that consider system-wise energy efficiency, we consider user-wise energy efficiencies and optimize them in a Pareto sense. However, due to the non-convexity of the formulated problem, finding the optimal solution is a challenging problem. To resolve the non-convexity of the problem, we propose to reduce the feasible set by including additional power constraints. Also, we show that the feasible set reduction technique preserves the optimality of the original problem. Simulation results show that the proposed scheme significantly enhances the energy efficiency of the cognitive users compared with the existing spectral-efficient designs.