Current solar energy systems design methods mainly rely on experts developing designs on 2D flat screens using outdated CAD models. Immersive 3D design methods may democratise the design process such that systems can be designed quickly and accurately. We measure user engagement or stress levels in both a 2D and 3D immersive virtual reality environment during a solar energy systems design task. User engagement was measured by estimating a user’s vital signs using a non-invasive FMCW radar. In our pilot study, four participants tried a 2D and 3D interface while their vital signs were being monitored.