Yet the domestic sector is not expected to continue growing as fast as it has, according to the 2015 Wind Technologies Market Report, published by the Department of Energy (DOE) in August.
New factories are unlikely to be added in the next five years because of international competition — and low global shipping costs — and because of uncertainty after the PTC expires in the early 2020s.
The US wind sector has more than 500 manufacturing facilities in 43 states, including eight utility-scale blade factories, nine tower plants, and four turbine nacelle assembly facilities.
They have the capability to produce more than 10,000 individual blades and more than 3,100 towers annually.
All the major turbine makers in the US market — GE, Vestas and Siemens — manufacture in the US.
The supply chain sector has in part grown then contracted over the years. There was 1.5GW of nacelle assembly capacity in 2006, and a high of more than 13GW in 2012, compared with 2015's 10.2GW. The sector grew especially rapidly from 2008 to 2010.
Meanwhile, imports of wind components more than tripled from 2013 to $2 billion in 2015, according to the DOE report.
That figure does not include gearboxes, so the trend is somewhat understated, says Dan Shreve, a partner at Make Consulting. Installations — and imports — were also unusually low in 2013 because of the PTC expiration.
According to the DOE report, the outlook for the domestic supply chain is mixed.
The report cites an upswing in the nearto medium-term expected growth, but highlights strong international competition and points out that the PTC that is being phased out.
"Although many manufacturers increased the size of their US workforce in 2015, market expectation for significant supply-chain expansion have become more pessimistic," concludes the report.
Ryan Wiser of the Lawrence Berkeley Laboratory, co-author of the DOE report, puts this down to the international pressure and the loss of tier two and three suppliers from the US market over the past five years.
"Outside of blades, towers and nacelle assembly from the three major OEMs, the other components internal to the nacelle are largely imported," Wiser said. But the domestic US manufacturing has stayed "pretty flat in recent years", mainly due to the strength of towers and blades, he added.
Only one new wind-related manufacturing facility opened in 2015, MM Composite, a parts manufacturer that had previously operated within the Siemens Fort Madison blade facility in Iowa.
Also announced in 2015 was a tower manufacturing plant in Amarillo, Texas, by GRI Renewables. That factory is expected to have up to 300 jobs and make up to 400 towers annually at full production.
Even so, at least three existing wind-turbine or component manufacturing facilities were consolidated, closed, or stopped serving the industry in 2015.
New manufacturing plants are unlikely to be established in the US over the next five years, said John Hensley, manager of industry data and analysis at the American Wind Energy Association.
That is because the outlook for the 2020s is "murky", with uncertain natural gas prices and electricity demand, and President Barack Obama's Clean Power Plan to regulate emissions from coal-fired power plants on hold, according to Hensley.
"We (also) express doubts that more factories for US turbine supply will be newly opened," said Bloomberg New Energy Finance (BNEF) analyst Alex Morgan. "This doesn't mean that within factories, additional production lines or more worker shifts can't be added.
"There is a chance that we see limited imports take some pressure off the domestic supply chain, particularly as we're running into overcapacity in Latin America," she added.
BNEF does not expect any bottlenecks in the supply chain, Morgan said. Indeed, in the US, several manufacturers expanded their workforce in 2015 to meet demand.
LM Wind Power remodelled facilities to meet industry standards, while Vestas and MFG Aberdeen started expanding existing facilities.
Make's Shreve is more sure of the prospect of growing imports. "The trend is consistent," he said. "Gearboxes, generators, bedplates: there are higher levels of offshoring."
He points to imports of nacelles from Spain, gearboxes and blades from China, towers from South Korea, Indonesia, Mexico, Spain and even Canada, and across-the-board imports of power generators and power converters, the latter of which is especially labour-intensive.
The current "extraordinarily" low shipping costs are a major factor, said Shreve. This is the result of an oversupply of cargo vessels for the past few years.
But it is hard to predict whether the imports will continue to expand as much over the next five years, he added. In a buoyant and competitive market, the priority for OEMs and developers is to keep landed costs of components as low as possible.