Optimization tools for long-term network planning, capable of incorporating flexible resources, require aggregated flexibility models that are not overly computationally expensive or complex. However, they should capture the operational benefits of flexibility sufficiently accurately for planning purposes. This paper examines the completeness of an aggregated flexibility model for planning tools by comparing it with a detailed flexibility model.

Two different constraint formulations, based on recovery period and temporal proximity, were tested to account for post-activation dynamics of flexibility resources. The results indicate that the recovery period-based formulation leads to an excessive reduction in demand. Conversely, the temporal proximity constraint formulation results in a realistic activation of flexibility resources, representing an improvement over the baseline formulation without constraints for post-activation dynamics. The findings demonstrate how an overly simplistic model of demand flexibility behavior can overstate its benefits as an alternative or supplement to network investments.