Laboratory tasks often focus on mechanical procedures leaving limited time and opportunities for students to build conceptual knowledge. We investigate to what extent introducing simulation tasks to preparation work can enable students to build their conceptual knowledge. We surveyed two cohorts of students taking an electronics module. Laboratory report marks were also analysed across the two cohorts (before and after introducing simulations in the laboratory preparation). No significant difference was found between the cohorts but the maximum marks increased after simulations were introduced. Students perceived that using simulations aided their constructive knowledge and knowledge confidence. Analysis of the free-text responses suggests that students benefitted from the simulation tasks by visualising the theory and concepts, confirming and checking results, and exploring different scenarios before and after the physical laboratory session. These results suggest that laboratory practicals should be supported with simulation software where possible.