Cross-border cannibalization: Spillover effects of wind and solar energy on interconnected European electricity markets

The average per-MWh revenue, or market value, of wind and solar energy tends to fall with increasing market share, as is now evident across European electricity markets. At the same time, these markets are becoming more interconnected. In this paper, we empirically study cross-border effects on the value of renewable energy: On one hand, interconnection is a flexibility resource that allows to export energy when it is locally abundant, benefitting renewables. On the other hand, wind and solar patterns are correlated between countries, so neighboring supply adds to the local one to depress domestic prices. We estimate both effects, using spatial panel regression on electricity market data from 2015 to 2023 from 30 European bidding zones. We find that domestic wind and solar value is not only depressed by domestic, but also by neighboring renewables expansion. The better interconnected a market is, the smaller the effect of domestic but the larger the effect of neighboring renewables. While wind value is stabilized by interconnection, the data suggest that solar value is not. These results can be used to estimate the impact of simultaneous domestic and neighboring capacity expansion: If wind market share increases both at home and in neighboring markets by one percentage point, the value factor of wind energy is reduced by just above 1 percentage point. For solar, this number is almost 4 percentage points.