Wind Turbine Tower Height Wind Speed Boost Calculator
Calculate wind speed boost from raising a turbine tower.
Use the wind shear power law to compare hub-height speeds at 30, 50, 80, or 100 feet up.
Wind Shear Power Law
Wind speed increases with height due to surface friction. The power-law model relates ground-level wind to hub-height wind:
V₂ / V₁ = (H₂ / H₁) ^ α
Where:
- V₁ = reference wind speed at H₁ (typically 10 m / 33 ft)
- V₂ = wind speed at hub height H₂
- α = wind shear exponent (depends on terrain)
Wind shear exponent (α) by terrain:
| Terrain | α (alpha) |
|---|---|
| Open water, smooth | 0.10 |
| Open prairie / smooth grassland | 0.14 |
| Crops, hedgerows | 0.17 |
| Suburban, trees | 0.22 |
| Wooded, complex terrain | 0.28 |
| Urban / built-up | 0.34 |
Why this matters for small wind turbines:
Power output scales with the cube of wind speed: Power ∝ V³
So a 25% increase in wind speed → (1.25)³ = 1.95× the power output, almost double.
Practical examples (10 mph at 33 ft, suburban α = 0.22):
| Hub Height | Wind Speed | Power Multiplier |
|---|---|---|
| 33 ft (10 m) | 10.0 mph | 1.0× (baseline) |
| 50 ft | 11.0 mph | 1.35× |
| 80 ft | 12.2 mph | 1.81× |
| 100 ft | 12.8 mph | 2.10× |
| 140 ft | 13.7 mph | 2.59× |
The “120-foot rule”: For most small-wind installations, every doubling of tower height adds ~30-50% more energy. Going from 60 ft to 120 ft typically improves output 30-45%, despite higher tower cost. Most small-wind experts recommend at least 80 ft of clearance above the highest obstacle within 500 ft.
Cost-benefit at hub height: A 100-ft monopole tower can cost 30-50% of total system cost. Industry rule: tower cost is typically justified if hub-height wind ≥ 11 mph annual average — the “Class 3” threshold.
Site assessment matters more than tower: A poor site with a 100-ft tower beats a great site with a 30-ft tower? Often yes — but not always. Always do a 1-year wind logger study before committing to a tall tower install.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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