Energy system modeling is highly relevant to support policymakers in defining strategies to achieve the European Green Deal targets towards carbon neutrality in 2050. Therefore, marginal CO₂ abatement cost curves are widely used in climate policy to assess the relationship between total cost changes and CO₂ emission reductions. Various methods exist for deriving abatement cost curves, leading to different results and policy implications. Most model-based methods derive smooth curves that can be transformed into step-wise curves through decomposition analysis, lacking system interactions at high temporal, sectoral, and techno-economic resolution. This paper overcomes these limitations by presenting a linear optimization approach with an hourly resolution to derive step-wise marginal CO₂ abatement cost curves for the German sector-coupled power system in 2030. Next to methodological insights, results indicate that early adoption of vehicle-to-grid ensures faster photovoltaic rooftop integration by reducing CO₂ abatement costs. Further, vehicle-to-grid replaces storage systems and decreases electricity generation costs while having no impact on CO₂ abatement costs of ground-mounted photovoltaic and onshore wind. Additionally, results show a high level of techno-economical detail and the least-cost sequential order of an optimal technology portfolio, allowing policymakers to formulate appropriate measures to achieve decarbonization targets.