Small wind / Buyer questions
Energy and economics
What capacity factor must a wind turbine achieve to meet my annual energy target?
The short answer
Divide the required annual energy by rated power multiplied by the hours in the year. The result is the capacity factor the project would need at the stated energy boundary. This calculation tests the requirement; it does not predict whether a turbine can achieve it. Compare that requirement with a site-specific energy assessment before choosing a model.
Work backward from the target
Illustrative arithmetic, not MARSTON performance: a project wants 20,000 kWh/year at the system AC output and is considering a 10 kW rating. In a 365-day year, continuous rated operation would give 10 × 8,760 = 87,600 kWh. The required annual net capacity factor is 20,000 ÷ 87,600 = 22.8%.
The target, rating and period must all use consistent units. If the target is useful energy delivered to a remote load, AC-output generation alone may not be the correct numerator: distribution, storage and surplus energy must also be considered.
Use the answer as a screening test
Suppose a separate assessment predicts 15,000 kWh at the same boundary. Its implied factor is 17.1%, so it does not meet the 20,000 kWh target under those assumptions. Raising the assumed factor in a spreadsheet will not fix the shortfall. Investigate another turbine, a different installation position, lower demand or a wider supply mix.
A result that looks modest is not automatically achievable. Wind-speed distribution, the applicable power curve, tower height, downtime and losses determine the estimate.
Keep generation and load coverage separate
Meeting the annual total does not establish uninterrupted supply or a particular self-consumption percentage. A project can meet its annual kWh target yet need the grid during calm periods and export during windy ones.
Record three separate checks: the required annual net capacity factor, the assessment supporting the expected factor, and the time-based match between wind output and demand. Keep uncertainty visible rather than presenting the reverse calculation as proof of production.
Sources
Examples are illustrative. Confirm product-specific performance, compatibility and supply scope in the applicable documents.