Developing quantum-dot cellular automata (QCA) digital circuits reversibly leads to substantial reductions in energy dissipation. However, this is usually accompanied by time delays and accompanying increases in the circuit cost metric. In this study, an innovative, partially reversible design method is presented to address the latency and circuit cost limitations of reversible design methods. The proposed partially reversible design method serves as a middle ground between fully reversible and conventional irreversible design methodologies. Compared with irreversible design methods, the partially reversible design method still optimises energy efficiency. Moreover, the partially reversible design method improves the speed and decreases the circuit cost in comparison with fully reversible design techniques. The key ingredient of the proposed partially reversible design methodology is the introduction of a partially reversible majority gate element building block. To validate the effectiveness of the proposed partially reversible design approach, a novel partially reversible half-adder circuit is designed and simulated using the QCADesigner-E 2.2 simulation tool. This tool provides numerical results for the circuit input/output response and heat dissipation at the physical level, within a microscopic quantum mechanical model.