Wind Turbine Calculator: How Much Will a Small Turbine Produce?
Enter the turbine’s rated power and your average wind speed. The calculator scales the rating with the cube of wind speed to estimate watts and daily watt-hours. As a guide, a 400 W turbine rated at 12 m/s makes roughly 15 W at 4 m/s, or about 356 Wh a day in steady wind.
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This calculator estimates how much energy a small wind turbine produces at your average wind speed. Enter the turbine’s rated power and the wind you expect at rotor height. It scales the rating with the cube of wind speed, which is why the result is usually far below the number in the product title.
Estimated average output: 0 W · 0 Wh/day · 0 kWh/year
Formula: average power ≈ rated power × (average wind ÷ rated wind)³ × 1.9, capped at rated power. The 1.9 factor accounts for wind variability (Rayleigh distribution). It is an optimistic estimate: obstacles, mast height and turbulence reduce it.
How does the calculation work?
Output ≈ rated W × (your wind speed ÷ rated wind speed)³. The power in the wind rises with the cube of its speed, so small changes in wind make big changes in output. Multiply by 24 to get Wh per day in steady wind.
Small-turbine ratings are typically reached at around 11-13 m/s. None of the turbine listings in our US catalog publishes a rated wind speed, so we use 12 m/s as a reasonable middle.
Example: a 400 W turbine at a steady 5 m/s gives 400 × (5 ÷ 12)³ ≈ 29 W, or about 694 Wh a day. At 4 m/s, it gives about 15 W, or 356 Wh a day.
How do I read the result?
Compare the daily Wh with your needs and with what solar would give.
| Daily estimate | What it usually means |
|---|---|
| Under 300 Wh | A trickle charge; solar is almost certainly the better buy |
| 300-800 Wh | A useful winter or night-time supplement to solar |
| Over 800 Wh | A strong site; wind can be a real part of an off-grid system |
For comparison, a 200 W solar panel makes about 600 Wh on a day with 4 peak sun hours (200 × 0.75 × 4). See are small wind turbines worth it? for the full comparison.
What makes real output differ from the estimate?
Site, height and equipment.
- Turbulence: trees, roofs and buildings slow and disturb the wind. Mount the turbine high and clear.
- Start-up speed: below it, the turbine makes nothing. Four of the six turbines we list declare 2.5 m/s.
- Controller: an MPPT controller extracts more energy across changing speeds than a basic one.
- Gusts: variable wind carries more energy than its average suggests, which partly offsets the losses above.
What should I do with the result?
If it clears a few hundred Wh a day, compare turbines; if not, look at solar first. Our best small wind turbines ranks the six models in our catalog, and the off-grid cabin picks show how wind pairs with solar. To store the energy, size a battery with the battery calculator.
Frequently asked questions
How do I estimate wind turbine output?
Multiply the rated power by (your wind speed ÷ rated wind speed) cubed, then by 24 hours for a daily figure. If the rated wind speed is not published, 12 m/s is a reasonable assumption for small turbines.
What average wind speed should I enter?
The average at the height where the rotor will be. Ground-level or airport readings can differ a lot from your site, especially near trees and buildings.
Why is the estimate so much lower than the turbine’s rating?
Because power rises with the cube of wind speed. At one third of the rated wind speed, a turbine makes about one twenty-seventh of its rated power.
How accurate is the estimate?
It is an order of magnitude. Gusty wind can add energy, while turbulence, start-up thresholds and controller losses reduce it. Treat it as a planning figure, not a promise.