[en] The German market has seen a plunge in wholesale electricity prices from 2007 until 2014, with base futures prices dropping by more than 40%. This is frequently attributed to the unexpected high increase in renewable power generation. Using a parsimonious fundamental model, we determine the respective impact of supply and demand shocks on electricity futures prices. The used methodology is based on a piecewise linear approximation of the supply stack and time-varying price-inelastic demand. This parsimonious model is able to replicate electricity futures prices and discover non-linear dependencies in futures price formation. We show that emission prices have a higher impact on power prices than renewable penetration. Changes in renewables, demand and installed capacities turn out to be similarly important for explaining the decrease in operation margins of conventional power plants. We thus argue for the establishment of an independent authority to stabilize emission prices. - Highlights: •We build a parsimonious fundamental model based on a piecewise linear bid stack. •We use the model to investigate impact factors for the plunge in German futures prices. •Largest impact by CO_2 price developments followed by demand and renewable feed-in. •Power plant operating profits strongly affected by demand and renewables. •We argue that stabilizing CO_2 emission prices could provide better market signals.