This assessment aims to analyze, illustrate, and examine the complexity and confidence problem associated with monitoring dynamic energy systems and managing them through model coupling and reduction. The confidence problem, which is related to the proximity of models to reality, can be reduced in general by considering neglected secondary domains by coupling their models to that of the main domain. Moreover, the complexity must be properly accounted for in the system models without decreasing the monitoring efficiency, which can be done through appropriate numerical model reduction techniques. In the article, after having posed the problem to be solved, we discussed and analyzed the automated procedures involved in energy systems. The notions of complexity and confidence in these systems are then illustrated and analyzed. In this framework, a complete coupled physical model reducing the confidence problem is then discussed and demonstrated. Model reduction strategies needed to optimize matching in automated procedures are then reviewed and analyzed. Finally, the pairing behavior of digital twins involving complex procedures is discussed and assessed, using a literature review. At the end of the paper, the case of electric and intelligent vehicles is discussed as an example of energy systems.