Annual energy production
The total energy a turbine or site delivers over a year, and the figure almost every commercial decision in wind is ultimately measured against.
Annual energy production, universally shortened to AEP, is the megawatt-hours a machine or a site delivers across a full year. It is the number in the financial model, the number a power purchase agreement is sized against, and the number an operator is judged on. Everything else in performance analysis is a means of explaining a change in it.
A full year is the shortest honest measurement period, because wind resource has a strong seasonal shape. Comparing one quarter against the previous quarter mostly measures the weather. This is also why an assessment built on a single year of history should be read with care: one year is one winter, and an unusually calm or unusually stormy season is inside the record rather than averaged out of it.
AEP is estimated before a site is built and measured afterwards, and the two rarely agree exactly. Pre-construction estimates are expressed as exceedance probabilities such as P50 and P90; measured production reflects what actually happened, including curtailment, outages, and the accumulated effect of losses that no alarm ever reported.
The reason performance work matters commercially is that recovered AEP is the cheapest energy available to an operator. A megawatt-hour recovered from an existing machine requires no new turbine, no new interconnection, and no capital project, which is why a few percent of underperformance across a fleet is worth more than it sounds.
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