"There are two plausible explanations for the observed decline in average load factors as wind farms age. The first is that the turbines become less efficient o

"There are two plausible explanations for the observed decline in average load factors as wind farms age. The first is that the turbines become less efficient over time as a result of mechanical wear and tear, erosion of the turbine blades and related factors. The second is that the turbines experience more frequent breakdowns and their operators take more time to bring them back into service because they are less concerned about the performance of older plants. Both reasons may be relevant in different circumstances and it is not possible to identify a primary explanation from the data. "