	Introduction

Rising energy prices and concern over greenhouse gas emissions have focused congressional attention on energy alternatives, including wind power. Although wind power currently provides only a small fraction of U.S. energy needs, it is growing more rapidly than any other electricity source. A national RPS requirement has been considered and, to date, rejected by Congress. Costs have declined, making wind more competitive with other power generation options. The Rise of Wind

Wind power is no longer an "alternative" source of energy in many regions of the country. Only the amount of new natural gas-fired generating capacity installed during this period exceeded that of wind. In 2007 the U.S. wind power industry brought over 5,000 megawatts of new generating capacity on-line, the largest annual increase ever by any country. Wind power's growth is driven by a combination of the following:
improvements in wind energy technology, high and volatile fossil fuel prices, the federal wind production tax credit (PTC) incentive, state renewable portfolio standards (RPS), difficulty siting and financing new coal-fired power plants given expectation of a future carbon constraint, and consumer preference for renewable energy. Drawbacks

A key challenge for wind energy is that electricity production depends on when and how consistently winds blow rather than when consumers most need power. This variability can create added expenses and complexity in balancing supply and demand on the grid. Several recent studies note that system integration costs do not become significant ($3 to $5 per megawatt-hour) until wind turbines account for 15-30% of the capacity in a control area. Another concern is that new transmission infrastructure may be required to send the wind-generated power to where it is needed. This can be an expensive and time-consuming effort. There are debates over how construction costs should be allocated among end users and which pricing methodologies are most economically efficient. Many in the industry believe that the on-again, off-again nature of the federal PTC incentives harm rational development of the sector. In summary, wind technology has evolved over the past two decades, resulting in larger, more reliable machines. Wildlife Constraints

The main environmental objection to wind power is concern about bird and bat collisions with wind turbines. Continued expansion of wind power in the United States could be slowed by the current financial crisis, lack of transmission capacity, or expiration of the federal renewable production tax credit on December 31, 2009. The credit is currently available to new wind, geothermal, and several other renewable energy sources.
Rising energy prices and concern over greenhouse gas emissions have focused congressional attention on energy alternatives, including wind power. Although wind power currently provides only about 1% of U.S. electricity needs, it is growing more rapidly than any other energy source. In 2007, over 5,000 megawatts of new wind generating capacity were installed in the United States, second only to new natural gas-fired generating capacity. Wind power has become "mainstream" in many regions of the country, and is no longer considered an "alternative" energy source.
Wind energy has become increasingly competitive with other power generation options, although the impacts of the current financial crisis are uncertain. Wind technology has improved significantly over the past two decades. CRS analysis presented here shows that wind energy still depends on federal tax incentives to compete, but that key uncertainties like climate policy, fossil fuel prices, and technology progress could dominate future cost competitiveness.
A key challenge for wind energy is that electricity production depends on when winds blow rather than when consumers need power. Wind's variability can create added expenses and complexity in balancing supply and demand on the grid. Recent studies imply that these integration costs do not become significant (5%-10% of wholesale prices) until wind turbines account for 15%-30% of the capacity in a given control area. Another concern is that new transmission infrastructure will be required to send the wind-generated power to demand centers. Building new lines can be expensive and time-consuming, and there are debates over how construction costs should be allocated among end-users and which pricing methodologies are best.
Opposition to wind power arises for environmental, aesthetic, or aviation security reasons. New public-private partnerships have been established to address more comprehensively problems with avian (bird and bat) deaths resulting from wind farms. Some stakeholders oppose the construction of wind plants for visual reasons, especially in pristine or highly-valued areas. A debate over the potential for wind turbines to interfere with aviation radar emerged in 2006, but most experts believe any possible problems are economically and technically manageable.
Federal wind power policy has centered primarily on the production tax credit (PTC), a business incentive to operate wind facilities. The PTC is currently set to expire on December 31, 2009. Analysts and wind industry representatives argue that the on-again off-again nature of the PTC is inefficient and leads to higher costs for the industry. A federal renewable portfolio standard—which would mandate wind power levels—was rejected in the Senate in late 2007; its future is uncertain.
If wind is to supply up to 20% of the nation's power by 2030, as suggested by a recent U.S. Department of Energy report, additional federal policies will likely be required to overcome barriers, and ensure development of an efficient wind market.