The number of new windpower installations in the US last year was high. This year, as companies chase the as yet unextended production tax credit (PTC), build is ramping up, according to Windpower Intelligence figures for projects with power purchase agreements aiming to complete in 2012.

The 2013-2020 figures below, also from Windpower Intelligence, Windpower Monthly's specialist research division, show projects that are proposed, using data provided by the developer.

As with any data based on predictions, these pipeline figures are more useful as an indication of the state of the industry than as an accurate figure of how much capacity will be added. Many proposed projects will not be built.

Last year, Make Consulting, Bloomberg New Energy Finance and BTM published estimates for 2013 wind installations of 5.9-8GW. Assuming the most optimistic 8GW, and applying that figure yearly until 2020, would see a total build of 64GW, about one third lower than pipeline plans.

Although growth will occur irrespective of the PTC, if the tax credit does lapse at any stage before 2020, installations will dip accordingly, as they have so many times in the past. In this case, even the 64GW figure may prove optimistic.