In Germany’s power market, electricity prices have traditionally risen in lockstep with gas because a combined‑cycle gas turbine (CCGT) usually sits on the margin. The short‑run marginal cost is calculated as TTF gas × 1.8 plus CO₂ allowances × 0.35, reflecting a plant that burns 1.8 MWh of gas and emits 0.35 t CO₂ per MWh generated. This formula sets a floor below which CCGT units rarely bid.

Decoupling occurs when renewable output—wind and solar—displaces gas from the marginal position enough that the annual average electricity price drifts below the gas‑implied level. Analysts flag a year as decoupled once actual prices sit more than 20% under that calculated benchmark. Either the current or most recent completed year meeting this gap triggers a “YES” verdict. The threshold accounts for occasional gas‑driven pricing while still signalling a meaningful shift.

The study draws day‑ahead auction data from Fraunhofer ISE, TTF gas averages from ICE/IEA, and EU ETS allowance prices from EEX. Volume‑weighting gives prominence to low‑price hours, meaning the decoupling signal reflects periods when renewables dominate dispatch. With Germany edging past the 20% gap, policymakers can argue that the power system is less vulnerable to gas market shocks. Stakeholders cite the metric to assess the effectiveness of Germany’s renewable subsidy scheme and grid integration plans.