Rooftop Wind Speed Estimator
Honest wind-at-roof-height numbers for urban small-wind dreams — suburban shear correction.
Rooftop turbines mostly disappoint, and this calculator shows why before you spend: urban shear (α≈0.30) means a 10 m airport reading of 4 m/s is barely 3.4 m/s at a 6 m roof — and cube-law power makes that a rounding error. If the result here is under 4.5 m/s, solar wins. Every time.
The power-law profile is why hub heights keep growing: raising hub height from 80 to 120 m over cropland (α≈0.2) adds ~8% wind speed — but ~27% more power. Measure α on site from two anemometer heights when possible; tabulated values mislead in complex terrain.
Engineering estimate from published standards and typical equipment data. Site conditions, equipment datasheets and measured data govern the real result — confirm with a qualified engineer.
Use the free Rooftop Wind Speed Estimator online — Honest wind-at-roof-height numbers for urban small-wind dreams — suburban shear correction. Runs instantly in your browser: no signup, no upload, mobile-friendly.
About Rooftop Wind Speed Estimator
Rooftop turbines mostly disappoint, and this calculator shows why before you spend: urban shear (α≈0.30) means a 10 m airport reading of 4 m/s is barely 3.4 m/s at a 6 m roof — and cube-law power makes that a rounding error. If the result here is under 4.5 m/s, solar wins. Every time.
How to use Rooftop Wind Speed Estimator
- 1Enter a measured wind speed and its measurement height.
- 2Set the target (hub) height and the terrain exponent.
- 3Read the extrapolated speed and the power-density multiple.
Why use Rooftop Wind Speed Estimator?
- ✓Hellmann power-law with terrain-correct exponents
- ✓Cube-law power impact shown alongside the speed change
- ✓Terrain presets from open sea to city suburbs
- ✓Explains tall towers in one calculation
Frequently asked questions
How does wind speed change with height?+
By the power law v₂ = v₁(h₂/h₁)^α, with α from ~0.10 offshore to ~0.30 over suburbs. Going 10 m → 100 m over farmland (α=0.2) multiplies speed ×1.58 — and power ×3.9, because power cubes the speed. Height is the cheapest wind upgrade there is.
What shear exponent should I use?+
Open sea 0.10, open plains 0.14 (the classic 1/7th law), cropland with hedges 0.20, forest/suburb 0.25–0.30. Best practice: derive α from two measurement heights on site — tabulated values mislead in complex terrain, where the power law itself degrades.
Can I use airport wind data for my site?+
As a starting estimate: airports measure at 10 m in open terrain. Extrapolate to your hub height with the right α — then remember your terrain differs from the airport's. For investment decisions, nothing replaces on-site measurement; for screening, this is the honest first pass.
Why are wind turbine towers getting taller?+
The shear math: each terrain has more speed higher up, and the cube law triples small speed gains into big energy gains. Over forested or built terrain (high α), a 140 m tower can harvest economic wind where an 80 m tower can't — towers are buying α^cubed.
Embed Rooftop Wind Speed Estimator on your website
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