Wind Turbine Calculator

A well-sited 5 kW domestic wind turbine in a good location (mean wind speed 6+ m/s) can generate 8,000-15,000 kWh per year. In a poor location (urban, sheltered, mean speed below 4 m/s), the same turbine might generate only 1,000-3,000 kWh. Wind speed is the critical factor — energy increases with the cube of wind speed.

Wind speed increases with height due to reduced surface friction. The relationship follows a power law: V(h) = V(10) x (h/10)^alpha, where alpha depends on terrain roughness. In urban areas (alpha 0.35), increasing from 10m to 20m hub height increases wind speed by about 27%, and energy by about 105%.

Capacity factor is the actual energy produced as a percentage of the theoretical maximum (if running at rated power 24/7). Small UK wind turbines typically achieve 10-25% capacity factor. A 5 kW turbine at 20% CF generates 8,760 kWh/year. Capacity factor depends primarily on wind speed at the site.

In England, a domestic wind turbine can be permitted development (no planning application) if it meets the limits in GPDO 2015 Schedule 2 Part 14. Class H covers a turbine mounted on or attached to a building: no more than 3m above the highest part of the roof, or 15m overall, whichever is lower, and at least 5m from any boundary. Class I covers a standalone turbine: overall height no more than 11.1m, and it must be set back from any point on the curtilage boundary by at least its overall height (including blades) plus 10% of that height — roughly 12.2m for a maximum-height turbine, not the 5m that applies to Class H. Both classes also require the lowest blade tip to be at least 5m above ground, a swept blade area of no more than 3.8 m², compliance with the MCS Planning Standards, and only one turbine per curtilage. Listed buildings, scheduled monuments and Article 2(3) land are excluded — Class H excludes conservation areas, AONBs, National Parks and World Heritage Sites, while Class I excludes the same except conservation areas (a standalone turbine can be permitted development in a conservation area). Any turbine that exceeds these limits needs full planning permission. Scotland, Wales and Northern Ireland have separate permitted development regimes — confirm with your local planning authority. All MCS-certified installations must also meet the MCS 020 Planning Standard 42 dB(A) noise limit at the nearest window.

The NOABL wind speed database (available at RenewableUK) gives estimated mean wind speeds at 10m, 25m, and 45m heights for any UK location. More accurate data requires an anemometer installed at hub height for at least 12 months. Urban locations are typically much windier at height than ground level suggests.