Abstract Energy models are crucial for helping governments and policymakers plan long-term investments in the energy transition context. One of the most established open-source optimisation models is OSeMOSYS—the Open-Source Energy Modelling System. This paper presents a new interface—clicSAND—for OSeMOSYS, which shortens the learning curve and supports beginner energy modellers to perform long-term investment analyses efficiently. The freely available and open-source clicSAND software consists of a user-friendly Excel interface for entering data, powerful solvers, and a dashboard for visualising results. The results, which extend to 2070, can inform policy decisions and mobilise financial resources for sustainable development measures—for example, ensuring affordable and secure energy supply and mitigating the effects of climate change. This paper describes clicSAND's main benefits, architecture, and functionalities. Furthermore, a South-African case study undertaken by participants of the international capacity-building event—the EMP-A (Energy Modelling Platform for Africa) 2021—shows the results achieved by inexperienced users following a three-week training course. Finally, current applications and future extensions of the software are also presented.