NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Cost of Wind Energy in the 

United States: Trends from 

2007 to 2012

M. Maureen Hand, Ph.D.

January 14, 2015

3rd Wind Energy Systems Engineering Workshop

Boulder, Colorado, USA

PR-6A20-63502
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Disclaimer

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This work was supported by the U.S. Department of Energy under Contract No. DE-AC36-08-GO28308 with the National Renewable Energy Laboratory.
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Outline

• Cost of energy trends in the United States

• U.S. technology trends from 2007 to 2012

o Project, turbine, rotor, hub height, specific power, and 

International Electrotechnical Commission (IEC) class

o Annual average wind speed and energy production

• System analysis considerations

o The impact of physical characteristics on cost of 

energy

o European technology trends from 2007 to 2012

o Taller towers for the southeastern United States.
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U.S. Cost of Wind Energy Trending Downward

4

$0

$20

$40

$60

$80

$100

$120

Jan-96Jan-97Jan-98Jan-99Jan-00Jan-01Jan-02Jan-03Jan-04Jan-05Jan-06Jan-07Jan-08Jan-09Jan-10Jan-11Jan-12Jan-13Jan-14

PPA Execution Date

 Interior (18,178 MW, 192 contracts)

 West (7,124 MW, 72 contracts)

 Great Lakes (3,044 MW, 42 contracts)

 Northeast (1,018 MW, 25 contracts)

 Southeast (268 MW, 6 contracts)

Levelized PPA Price (2013 $/MWh)

75 MW

150 MW 50 MW

After a brief period of increasing 

costs coupled with increasing 

annual deployment, the 

downward cost of energy 

trajectory returns and is 

expected to continue in 2014.

Power purchase agreements 

(PPAs) reflect long-term prices 

for electricity after accounting 

for incentives, such as the 

production tax credit, whereas 

cost of energy represents an 

expected investment to bring a 

plant to commercial operation.

Source: Bolinger and Wiser 2014

Source: Wiser and Bolinger 2014
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Project and Turbine Size

• U.S. project size remained relatively similar from 2007 to 2012 with a wide 

range.

• Turbine size increased from 2007 to 2012 on average and the range 

increased as well.

Source: LBNL Wind Project Database
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Rotor Diameter and Hub Height

• Average rotor diameter increased 25% between 2007 and 2012 and the range of 

options was greater in 2012.

• The majority of hub heights were at 80 meters (m) over the entire period, with some 

upward trend in 2012. 

Source: LBNL Wind Project Database
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Specific Power and IEC Class

• Since 2007, specific power has decreased such that the 25th‒75th percentile in 2012 was 

lower than the 25th percentile in 2008. The range has grown because of a variety of rotor 

options and an increased average machine rating. In 2013, the average specific power was 

255 watts (W)/m2.

• Since 2007, there has been a trend toward using Class 2–3 turbines; in 2013, almost all 

turbines were Class 2/3–3.

• In general Class 3 turbines are designed for lower wind speed sites and have lower specific 

power.

Source: LBNL Wind Project Database
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Average Annual Wind Speed and Energy Production

• Average annual wind speed for projects installed in 2012 was lower than projects 

installed in 2007. Full load hours in 2012 were slightly higher than 2007, but 

generally similar. 

• Energy gains anticipated from the decrease in specific power are largely offset by the 

decrease in average wind speed. 

• A few projects built in 2013/2014 used low specific power rotors in higher wind 

speed sites with expectations of capacity factors near 50%.

0%

10%

20%

30%

40%

50%

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

2007 2008 2009 2010 2011 2012

Capacity Factor

Full Load Hours

Year

generation-weighted average, not index weighted

generation-weighted average, wind index weighted

Source: LBNL Wind Project Database
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Cost of Energy is Impacted by Physical Characteristics

Parameters Reference 

Project

Taller 

Tower Larger Rotor

Taller Tower 

and Larger 

Rotor

Higher 

Wind 

Speed

Combination

Nameplate 

(megawatts [MW]) 1.9 1.9 1.9 1.9 1.9 1.9

Rotor diameter (m) 96.9 96.9 110 110 96.9 110

Hub height (HH) (m) 82.7 100 82.7 100 82.7 100

Avg. speed at 50 m 

(m/s) 

(Avg. speed at HH)

7.25 

(7.79)

7.25 

(8.0)

7.25 

(7.79)

7.25 

(8.0)

8.0 

(8.6)

8.0

(8.8)

Annual energy 

production (AEP) 

(MWh/MW/yr)

3,410 3,536 3,796 3,918 3,866 4,345

Capacity factor 38.5% 40.4% 43.3% 44.7% 44.1% 49.6%

Levelized cost of 

energy (LCOE)* 

($/MWh)

66 64 60 58 59 52

*CapEx = $1728/kW; OpEx = $50/kW; Fixed charge rate (FCR; real, after tax) = 10.2%; 

 LCOE = ((FCR*CapEx) + OpEx)/AEP

• Adjusting physical characteristics that affect annual energy production (AEP) in isolation of 

impact on capital and operating costs illustrate the relative impact on the levelized cost of 

energy (LCOE). 

• Full system analysis is needed to represent the cost and performance trade-off that is required 

to precisely determine cost-of-energy impacts.

Source: NREL Analysis Using Cost and Scaling Model from Fingersh et al. 2006
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Reduced Cost of Energy Observed in Europe, But 

Technology Trends Differ from the United States

Source: European Commission-Joint Research Centre Wind Project Database

• Specific power was largely constant from 2007 to 2012 while tower height increased. 

In the United States, specific power declined while tower height remained constant.

• System analysis is required to investigate the motivations behind these different trends. 

Questions for this analysis include: 

• To what extent do land-use constraints incentivize one pathway over another?

• How are capital investments affected by increasing turbine rotor options versus 

tower options?

• Will operation and maintenance costs be impacted differently by taller towers or 

siting low specific power turbines in a variety of wind resource conditions?
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Continued Turbine Scaling in the United States Limited 

by Transportation and Logistics Restrictions

• Tower diameter, tip height, blade length and chord width, and nacelle weight are approaching limits 

that strain transport, installation, and regulatory systems and prevent continued turbine scaling.

• Addressing these transportation and logistics challenges is expected to enable the deployment of 

larger wind turbines on taller towers, which could greatly enhance the deployment of wind energy 

into low- and moderate-wind-speed regions of the United States. 

• System analysis is required to investigate these trade-offs both regionally and nationally.

Source: Cotrell et al. 2014. 
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Conclusions

• Technology trends that increase energy capture 

such as lower specific power, taller towers, and 

higher wind speed sites all lead to lower cost of 

wind energy.

• Understanding the trade-offs between the cost 

and performance behind recent trends in the 

United States and Europe or in anticipation of 

future trends requires system analysis.

• System analysis is needed to explore 

implications on land-use constraints, capital 

investment, and operating costs, as well as 

energy capture.
Thank you!

M. Maureen Hand, Ph.D.

maureen.hand@nrel.gov
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References

• Bolinger, M.; Wiser, R. (February 10, 2014). Internal memorandum. Lawrence Berkeley 

National Laboratory.

• Cotrell, J.; Stehly, T.; Johnson, J.; Roberts, J.O.; Parker, Z.; Scott, G.; Heimiller, D. (2014). 

Analysis of Transportation and Logistics Challenges Affecting the Deployment of Larger Wind 

Turbines: Summary of Results. TP-5000-61063. Golden, CO: National Renewable Energy 

Laboratory. Accessed January 10, 2015: http://www.nrel.gov/docs/fy14osti/61063.pdf.

• European Commission-Joint Research Centre Wind Project Database. (2015). Graphics 

produced by Roberto Lacal-Arantegui.

• Fingersh, L.; Hand, M.; Laxson, A. (2006). Wind Turbine Design Cost and Scaling Model. TP500-40566. Golden, CO: National Renewable Energy Laboratory. Accessed January 10, 2015: 

http://www.nrel.gov/docs/fy07osti/40566.pdf.

• Bolinger, M.; Wiser, R; (February 10, 2014). Internal memorandum. Lawrence Berkeley 

National Laboratory.

• LBNL Wind Project Database. (2014). Graphics produced by Ryan Wiser.

• Wiser, R.H.; Bolinger, M. (2014). 2013 Wind Technologies Market Report, Lawrence Berkeley 

National Laboratory.