Vattenfall AB owns wind farms in Denmark, Germany, Sweden, in the UK and in the Netherlands. Installed wind power capacity in the UK is 590 MW (6 wind farms with a total of 180 turbines). Annual electricity generation in wind power farms amounts to 128 GWh onshore and to 1554 GWh offshore, 1.7 TWh in total. The wind power plants operate at wind velocities between 4-25 m/s and generate electricity – generation recalculated to full capacity – in average 33 % of the year. To be able to supply electricity continuously wind power must be integrated in a system with other power technologies such as hydropower or thermal power. Wind power is a low carbon technology; it has an obvious visual impact in the landscape and causes some changes in biodiversity.