Small wind / Buyer questions
Energy and economics
Can a lower-rated wind turbine generate more annual energy than a higher-rated one?
The short answer
Yes, it is possible, but the actual comparison must use model-specific performance evidence at the same site. Rated power is one point or operating rating, while annual energy adds output across the wind conditions experienced over time. A turbine that performs better during frequent conditions can offset a disadvantage during less frequent conditions. Rotor dimensions and the complete power curve deserve attention alongside kW.
Follow the hours that matter
Do not compare only the rated wind speed or the largest output number. Divide the relevant wind record into consistent intervals or wind-speed bins, apply each turbine’s applicable output, and sum the resulting energy. Use consistent air-density assumptions, electrical boundaries and losses.
A wider rotor may capture more wind energy under some conditions, but rotor size alone does not prove an annual-energy advantage. Control behavior, conversion, operating limits and the tested performance information must remain part of the comparison.
See a deliberately invented comparison
Arithmetic illustration only: two hypothetical options have the following average outputs in three groups of hours. These are invented figures, not turbine power curves or MARSTON results.
| Hours | Option A output | Option B output |
|---|---|---|
| 4,000 | 0.8 kW | 0.4 kW |
| 3,000 | 2.5 kW | 2.0 kW |
| 1,000 | 5.0 kW | 8.0 kW |
With zero in the remaining 760 hours, A totals 15,700 kWh and B totals 15,600 kWh. B has the higher output in the strongest group, but A narrowly leads the year.
Ask for an auditable comparison
The example demonstrates a calculation principle, not which real model to buy. Ask for the underlying power curves, the common wind record and the loss ledger. Confirm whether the difference between estimates is larger than the uncertainty.
If both annual yields are close, installation, serviceability, electrical suitability and total project cost may decide the shortlist. Do not replace those checks with a blanket claim that either the lower or higher kW rating is always preferable.
Sources
- DOE Small Wind Guidebook: general assessment background
- DOE Small Community Wind Handbook: project planning background
Examples are illustrative. Confirm product-specific performance, compatibility and supply scope in the applicable documents.