The study, published by Fraunhofer ISE in November 2024, investigates pathways to achieve climate neutrality in Germany by 2045. Using the regionalised energy‑system model REMod, the authors simulate four future scenarios that differ in technological openness, efficiency measures, persistence of conventional power, and resilience to geopolitical shocks. The model represents Germany as ten regions, allowing detailed analysis of inter‑regional electricity and hydrogen flows and the integration of negative‑emission technologies such as BECCS, DACCS, and bio‑based fuels.

In the “technology‑open” scenario, the system is optimised for cost, resulting in a CO₂ avoidance cost of about €220 per tonne of CO₂. The “efficiency” scenario, which assumes accelerated deployment of renewables and stronger efficiency and sufficiency measures, reduces the CO₂ cost to roughly €90 per tonne. In contrast, the “persistence” scenario, characterised by continued investment in combustion technologies and delayed renewable expansion, yields a much higher CO₂ cost of approximately €320 per tonne. These figures illustrate the economic trade‑offs between different policy pathways and underline the importance of early renewable deployment.

Renewable generation dominates the projected energy mix. By 2045, wind power is expected to supply 60 % of electricity, while photovoltaic installations contribute 30 %. The study highlights that wind resources are strongest in northern states, whereas high electricity demand is concentrated in industrial regions such as North Rhine‑Westphalia, Baden‑Württemberg, and Bavaria. Consequently, the model predicts that inter‑regional electricity exchange will increase three‑ to six‑fold, necessitating substantial upgrades to high‑voltage transmission networks. Hydrogen is projected to be produced mainly in the north and transported to the south, requiring a nationwide hydrogen transmission and distribution grid to guarantee supply security across all states.

Sectoral analysis shows that the electricity, industry, building, and transport sectors are tightly coupled. The model incorporates power‑to‑gas, power‑to‑liquid, and power‑to‑X technologies, enabling flexible use of surplus renewable electricity. Hydrogen and synthetic fuels are positioned as key carriers for decarbonising heavy industry and long‑haul transport, while battery electric vehicles and heat pumps are favoured for the mobility and building sectors. The study also evaluates the role of negative‑emission technologies, estimating that a combination of BECCS, DACCS, and bio‑based fuels is required to meet the stringent 2045 CO₂ budget.

The research was conducted by a team of Fraunhofer ISE scientists—Thelen, Nolte, Kaiser, Jürgens, Müller, Senkpiel, and Kost—who expanded the REMod model to include regional transmission networks and a broader set of hydrogen technologies. The project was carried out within two Fraunhofer research programmes, with support from German federal research funding. The study’s findings provide a detailed, cost‑optimised blueprint for policymakers, highlighting the critical need for accelerated renewable deployment, grid expansion, and the integration of negative‑emission pathways to achieve Germany’s climate‑neutrality target.