The study, commissioned by the European Environmental Agency (EEA), finds that Europe’s wind-energy potential will be equivalent to 20 times its total energy demand in 2020. But a series of environmental, social and economic constraints mean that realistically the figure will be closer to three times total demand.

In December 2008, the European Parliament and Council approved a green-energy directive mandating that 20% of the bloc’s total energy supply comes from renewable sources. The European Commission separately set a goal of 12% for wind energy, which is the largest renewable generator outside hydropower.

Many inside and outside the renewables industry claim that such a target is unrealistically high, and could ultimately serve to undermine the rapidly growing wind sector. At the end of 2008, the EU 27 countries had 65 gigawatts of installed wind capacity, enough to meet 4.2% of total electricity demand.

The European Wind Energy Association predicts that there will be 80GW in place by 2010, and 180GW by 2020 – likely to be equivalent to between 11.6%-14.3% of total electricity demand.

While the EEA says that the amount of realistically accessed wind-energy potential in Europe is encouragingly high, it also states that the potential in many countries is practically non-existent. The UK and Ireland together have more than 5,000 terrawatt hours of 'competitive' wind resources that could potentially be on line by 2020. In contrast, six countries – including Switzerland, the Czech Republic, Hungary, Slovenia, Slovakia and Luxembourg – have none.

Reasons for the disparity range from natural factors -- including the amount of mountains, which are expensive to build wind farms on -- to infrastructure-related issues, such as the state of the existing electrical grids in various countries.

The UK has an unusually massive potential due to its offshore sites, which are wind dense and in shallow enough waters to keep down the cost of installation. Some countries, such as the Netherlands, have prohibited the construction of offshore wind farms within 22km of the coastline due to concerns about the visual impact they would have.