What metrics are usually used to quantify forecasted power error for weather-dependent renewables?

By | October 24, 2016

What metrics are usually used to quantify forecasted power error for weather-dependent renewables such as wind or PV?

I guess that there are at least two kinds of errors: where the magnitude of the forecast is wrong, and where the timing of the forecast is wrong. Something like a typical root mean squared error (RMSE) would seem to penalise a timing error twice over.

So how is the skill of a forecasting method quantified?