Climate change is making output from renewable energy projects harder to predict.

Fitch Ratings reported in March that a comparison of actual production numbers from solar projects that Fitch rated against the P50 forecasts found that 73% of such projects were performing within 5% or better of the original forecasts. Six percent were significantly below the forecasts. However, only 24% of wind projects were within 5% or better than the original forecasts. Nearly a third were more than 15% below.

A separate survey by kWh Analytics last fall found slightly different numbers for solar. kWh Analytics reported after reviewing 30% of the US solar fleet owned by 10 of the top 15 project owners that utility-scale solar projects were underperforming P50 output forecasts by 6.3% on average. (For more detail, see “Overestimation of solar output” in the October 2020 NewsWire.)