The performance of building-mounted wind turbines “is 5%-10% of manufacturer claims”, according to a study by the independent consultant Encraft

The world’s first year-long customer field trial looked at 26 grid-connected micro wind turbines from five manufacturers on sites across the UK between October 2007 and November 2008.

Encraft said the research suggested that a turbine’s performance would make a significant contribution to a building’s energy and carbon saving “only on the most exposed sites and tallest buildings”.

Other findings include:

  • the average energy generated per turbine per day is 214Wh, sufficient to power four 9W low energy lamps for five hours a day
  • the value of average power consumption produced per site per year, at a typical electricity cost of £0.1452 per kWh, is £33.39
  • the best performing turbine produced electricity worth £126.18
  • on the poorest site the electricity generated was less than the energy required to run the electronics of the turbine.

The report emphasises how much a turbine’s performance is linked to its location: turbines on high-rise sites generated as much energy in one month as other turbines in the trial did in one year.

Encraft specialises in microgeneration, on-site renewables and low carbon buildings. The trial was funded by Pilkington Energy Efficiency Trust, Warwick district council, BRE Trust and homeowners. It was supported by the Department of Enterprise, Trade and Investment, the British Wind Energy Association, Warwickshire county council, Action 21 and the Micropower Council.