Energy system models suggest optimal investment pathways and guide policymakers in implementing the low-carbon energy transition. Although model accuracy greatly improved over the last decade, it is unclear whether the cost of capital (CoC) is well represented, despite the parameter’s strong influence on model outcomes. In this perspective, we review 58 model-based publications that explicitly refer to CoC and observe that simply stating unfounded assumptions remains the most important “method” for determining the CoC. Overall, there appears to be a clear lack of guiding principles for how to appropriately determine CoC for use within models. To close this gap, we identify four barriers to a more accurate CoC reflection and suggest practical steps for overcoming them, including heuristic guidelines to support modelers in determining when differentiated CoC rates ought to be applied. Overall, we believe more rigorous treatment of the CoC will improve the quality of model-based policy advice.

能源系统模型建议最佳投资途径并指导政策制定者实施低碳能源转型。尽管模型准确性在过去十年中大大提高，但尚不清楚资本成本 (CoC) 是否得到很好的体现，尽管该参数对模型结果有很大影响。从这个角度来看，我们回顾了 58 份明确提及 CoC 的基于模型的出版物，并观察到简单地陈述没有根据的假设仍然是确定 CoC 的最重要的“方法”。总的来说，似乎明显缺乏指导原则来指导如何适当地确定在模型中使用的 CoC。为了缩小这一差距，我们确定了更准确的 CoC 反映的四个障碍，并提出了克服这些障碍的实际步骤，包括启发式指南，以支持建模人员确定何时应应用不同的 CoC 费率。总体而言，我们认为对 CoC 的更严格处理将提高基于模型的政策建议的质量。