>> What's interesting is they describe it working on forecasts (for wind and sun) instead of instantaneous renewable production. I wonder what the rationale for that was? Basing the algorithm on instantaneous information should be more accurate and thus give better savings

The article says they are “shifting the timing of our compute tasks”, so if they think that there will be cheap electricity later in the day (because it’s going to be especially windy or something) it would make sense for them to schedule some of their heavy compute tasks at that time, rather than right now.