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Yield & Yield Assessment

The expected annual energy production (AEP) is the key figure in any wind farm financing. Bankable yield assessments follow the FGW Technical Guideline 6 (TR6) and quantify uncertainties as P50/P75/P90 exceedance probabilities. We explain the methodology, measurement procedures, wake losses and new optimization approaches (AI / wake steering).

Sources: FGW e.V., TÜV Nord, DNV.

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Yield Assessment (FGW TR6)
Structure, requirements, accredited providers — what the bank wants to see.
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Wind Measurement (MEASNET)
LiDAR vs. met mast, 12-month campaign, long-term correction, IEC 61400-12.
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P50 / P75 / P90 explained
Exceedance probabilities, uncertainty budget, what investors and banks expect.
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Wake Losses & Array Efficiency
Up to 30% loss with an unfavorable layout — modeling, benchmarks, countermeasures.
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Layout Optimization
Iterative algorithms for turbine positions under minimum spacing, topography and prevailing wind direction.
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AI Yield Optimization
Wake steering, yaw/TSR control, predictive maintenance — potential and limits (YMYL caveat).
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Yield Estimation
From the preliminary estimate (wind atlas) to the bankable assessment — stages, accuracy, costs.
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Full-Load Hours (cross-reference)
Typical ranges in Germany by region, dependence on hub height and site quality.
Yield assessment methodology chain per FGW TR6: 5 steps wind measurement, long-term correction, flow model, power curve, P50/P75/P90. Normal distribution with P50 (median), P75, P90 marked. Uncertainty budget: wind measurement 3-5%, long-term correction 2-4%, flow model 2-6%, power curve 1-3%, availability 1-2%, total 8-12% RSS. P90 = bankable reference value, DSCR greater-than-or-equal 1.20

Yield assessment — methodology chain, uncertainty budget and P-values (FGW TR6)

Looking for a yield assessment or layout optimization?

Do you need a bankable yield assessment per FGW TR6, a wind measurement or a layout optimization for your wind farm project? We connect you with accredited assessors and specialized planning offices.

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Methodology & YMYL note

Yield assessments are the basis for multi-million-euro investment decisions. We provide no yield forecasts of our own; instead, we explain the methodology. All figures on these pages come from publicly available, citable sources (FGW, DNV, TÜV, Fraunhofer IWES). Caution: frequently cited AI additional-yield figures (12–17%) are best-case values under laboratory conditions — the annual AEP uplift of a real wind farm is considerably lower. Details under AI Yield Optimization.

Key terms

TermMeaning
FGW TR6Technical Guideline 6 of the Fördergesellschaft Windenergie (German wind energy promotion association) — the standard for yield assessments in Germany
MEASNETInternational association for wind-measurement quality assurance
P50Energy yield exceeded with a 50% probability (median expectation)
P90Energy yield exceeded with a 90% probability (conservative, used by banks)
Wake lossesYield reduction caused by wake turbulence from upstream turbines
Array efficiencyRatio of actual wind farm yield to the sum of individual turbine yields without interaction
Wake steeringDeliberate yaw movement of the upstream turbine to deflect its wake