Sunday's solar sent German prices to -€414/MWh. The solar generation forecast was missed by 10 GW - a fifth of demand.

Some of that became curtailment. But it also means you could've run a 10 GW data center for hours and been paid for the privilege. Or stored the surplus in batteries and earned twice.

Sunday was a rare case, but the forecast mismatch isn't - in France it’s roughly a 1 GW forecast delta nearly every day. Spain, Italy, Poland either have bad data or are sitting on a real opportunity - for storage or for trading, if you’re building better forecasts.