Wind Power

A wind turbine turns the kinetic energy of moving air into electricity through a rotor and a generator. Among non-hydro renewables only solar is growing faster. In 2025 wind generated about 2,700 TWh, roughly 8.5% of world electricity, up from around 830 TWh a decade earlier. Global installed capacity passed 1,000 GW in 2023 according to the Global Wind Energy Council, with China accounting for well over a third of it. Most of it is onshore. Offshore wind is smaller but growing fast, with more output per turbine and very different engineering and costs.

How a wind turbine works

A modern utility-scale turbine is a three-bladed, upwind, horizontal-axis machine. Wind flowing over the aerofoil-shaped blades creates lift, which turns the rotor at a relatively slow 5–15 revolutions per minute. The rotor drives a generator either through a gearbox (stepping speed up to around 1,000–1,500 rpm for a doubly fed induction generator) or directly, in the case of direct-drive machines with large permanent-magnet generators. Power electronics convert the variable-frequency output to grid frequency.

Three control systems keep the machine within safe limits. The yaw system rotates the nacelle to face the wind. Pitch control twists each blade about its long axis to regulate power above rated wind speed and to feather the blades in storms. In light winds, the generator torque controller holds the rotor at the best tip-speed ratio.

The power equation

The power in the wind rises with the cube of wind speed. That is why the choice of site matters more than anything else in wind economics:

Double the wind speed and you get eight times the power, so a site averaging 8 m/s yields roughly twice the energy of one averaging 6.3 m/s. Double the rotor diameter and the swept area quadruples. Hence the steady move to larger rotors and taller towers. Wind speed increases with height (wind shear), so a higher hub reaches stronger, steadier air.

The Betz limit exists because a rotor cannot stop the air completely: it must leave the downstream flow with enough velocity to clear the rotor plane. In theory, the best a rotor can do is slow the wind behind it to one third of its upstream speed. In practice the turbine follows a power curve: it starts generating at a cut-in speed of about 3 m/s, reaches nameplate output at a rated speed of roughly 11–13 m/s, and shuts down at a cut-out speed of about 25 m/s (some modern designs ramp down gradually up to 30 m/s instead of tripping).

Types and main variants

Onshore wind

New onshore turbines installed in the mid-2020s are typically 4–7 MW with rotor diameters of 140–175 m and hub heights of 100–160 m. “Low wind speed” models with very large rotors relative to generator size (a low specific power, in W per m² of swept area) have made inland sites in Germany, India and the US Midwest pay that didn’t a decade ago. Owners of older, smaller turbines on the best sites are repowering them: replacing, for example, ten 1 MW machines with three 5 MW machines often doubles or triples energy yield on the same land.

Fixed-bottom offshore wind

Winds at sea are stronger and less turbulent than over land, and road transport limits on blade length don’t apply, so offshore turbines are bigger. Commercial offshore machines are 12–15 MW with rotors of 220–240 m (for example, the Siemens Gamesa SG 14-222 DD and Vestas V236-15.0 MW); Chinese manufacturers have installed 16–20 MW units and announced prototypes above 20 MW. Foundations depend on water depth and seabed: monopiles (single large steel tubes, the dominant type in water up to about 40 m), jacket lattices for deeper or harder seabeds, and concrete gravity bases. Power is collected through array cables to an offshore substation and exported to shore, increasingly over HVDC links for projects far from the coast.

Floating offshore wind

Beyond 50–60 m of water, fixed foundations stop making economic sense. Floating offshore wind mounts a standard turbine on a buoyant platform held by mooring lines: spar buoys (deep ballasted cylinders, used at Equinor’s 30 MW Hywind Scotland, the first floating farm, in 2017), semi-submersibles (used at the 25 MW WindFloat Atlantic off Portugal) and tension-leg platforms. Equinor’s 88 MW Hywind Tampen, which supplies offshore oil and gas platforms in the Norwegian North Sea, was the largest floating farm when completed in 2023. According to the IEA’s Offshore Wind Outlook, the technical offshore wind resource is many times total world electricity demand, with much of it in deep water off Japan, the US West Coast, Korea and the Mediterranean.

Small and distributed wind

Turbines below about 100 kW serve farms, remote sites and microgrids. They make far less economic sense than utility-scale machines. Hubs sit low, and the cube law punishes the weaker wind near the ground. Most building-mounted micro turbines produce very little energy.

Efficiency and capacity factor

Peak aerodynamic efficiency tells you little about annual output. The number that counts is the capacity factor: actual annual energy divided by what the turbine would produce running at nameplate power for all 8,760 hours.

Capacity factor rises with average wind speed, hub height and lower specific power, and falls with wake effects inside large arrays (typically 5–15% energy loss for big offshore clusters), grid curtailment and downtime. Offshore availability is lower than onshore because weather limits access for repairs. Output follows the weather, which makes wind a variable renewable. How much it is worth to the grid depends on geographic spread, interconnection, storage and flexible demand. To estimate the yield of a specific turbine at a specific wind regime, use the wind turbine calculator, and for an array including wake losses, the wind farm calculator. The wind potential map shows mean wind speeds worldwide.

Costs

Between 2010 and 2020 wind costs fell sharply thanks to larger rotors, higher capacity factors and cheaper finance. According to IRENA’s Renewable Power Generation Costs in 2023 (published 2024), the global weighted-average LCOE of newly commissioned onshore wind fell to about USD 0.033/kWh in 2023, with total installed costs averaging around USD 1,160/kW. Offshore wind averaged about USD 0.075/kWh, with installed costs around USD 2,800/kW, though both figures vary widely between China (lowest) and Europe and the US.

Lazard’s LCOE+ 2024 gives an unsubsidised range of roughly USD 27–73/MWh for US onshore wind and USD 74–139/MWh for offshore. NREL’s Annual Technology Baseline provides US projections by wind resource class, showing onshore LCOE varying by more than a factor of two between the windiest and least windy sites. Then steel prices, interest rates and supply-chain bottlenecks pushed costs up between 2021 and 2023. Offshore took the worst of it: several US East Coast and UK contracts were cancelled or renegotiated because their fixed strike prices no longer covered costs. Floating wind still costs roughly two to three times as much as fixed-bottom. The industry expects steep declines once projects reach gigawatt scale.

Wind’s costs are mostly CAPEX. There is no fuel bill, and operating costs are typically 20–30% of LCOE onshore, more offshore. As a result wind LCOE reacts strongly to the discount rate: a rise in WACC from 5% to 8% raises LCOE by roughly a quarter. You can test these sensitivities in the LCOE calculator.

Land, water and materials

A wind farm covers a large area but physically occupies very little of it. NREL’s land-use survey of US wind projects found a total project area averaging about 34 hectares per MW (with wide variation) but a direct, disturbed footprint for foundations, roads and substations of well under 1 hectare per MW. The rest stays in farming or grazing. Offshore, the main spatial issues are shipping lanes, fishing grounds, military radar and seabed habitats.

Wind turbines use almost no water while running, a real advantage over thermal plants in drought-prone regions.

Per unit of capacity, wind needs more material than fossil plants. A turbine is mostly steel (tower and nacelle), concrete (onshore foundations), copper (generator and cables), cast iron and composites. Offshore installations need substantially more steel per MW because of monopiles and jackets. Direct-drive and many offshore turbines use permanent-magnet generators containing neodymium, praseodymium and dysprosium, and most of their mining and refining happens in China. Gearbox designs with induction or electrically excited generators avoid most rare earths.

Lifecycle CO2 emissions

Almost all of a wind turbine’s lifecycle emissions come from manufacturing steel, concrete and composites. The IPCC AR5 WGIII Annex III (2014) reports a median of about 11 gCO2e/kWh for onshore wind (range roughly 7–56) and 12 gCO2e/kWh for offshore (range roughly 8–35). UNECE’s 2021 life cycle assessment found values in a similar low range of roughly 8–23 gCO2e/kWh across onshore and offshore configurations, with floating designs at the top of the range because of their heavier structures. For comparison, gas combined-cycle plants emit around 400–500 gCO2e/kWh and coal 750–1,100. The energy payback time of a modern turbine is typically under one year of a 25–30-year life.

Safety and environmental impacts

Human safety. Per unit of electricity, wind is among the safest energy sources. Our World in Data, drawing on Markandya & Wilkinson (2007) and later studies, puts the death rate at a few hundredths of a death per TWh, mostly workers hurt during construction and maintenance. Blade failures and ice throw are rare, and setbacks and icing detection handle them.

Birds. Turbines do kill birds, but far fewer than other human causes. Studies for the United States estimate roughly 140,000–500,000 bird deaths per year at turbines, against an estimated 365–988 million from building collisions and over a billion from cats. The problem is concentrated at specific sites: raptors at Altamont Pass in California and Smøla in Norway, where one study found painting one blade black reduced bird fatalities by about 70%. The main fixes are siting turbines away from migration corridors and shutting them down when radar detects birds.

Bats. Bats are more vulnerable than birds. Collisions and pressure changes near the blades kill them, especially migratory tree bats on calm late-summer nights. Raising the cut-in speed by 1.5–3 m/s during high-risk periods typically cuts bat fatalities by half or more for an energy loss of around 1% or less.

Noise and visual impact. A modern turbine produces roughly 35–45 dB(A) at 300–500 m, comparable to a quiet room or rural background at night. Most jurisdictions set minimum setbacks or noise limits. Shadow flicker is controlled by automatic shutdown at critical sun angles. What drives most local opposition and permitting delays is how turbines change the view.

Marine impacts. Offshore pile driving produces intense underwater noise that can harm porpoises and seals; bubble curtains and seasonal restrictions reduce it. Foundations act as artificial reefs, and fishing exclusion can benefit fish stocks, though some fisheries lose access.

End-of-life and blade recycling. Steel, iron and copper are recycled at high rates. Blades are harder: a widely cited estimate (Liu & Barlow, 2017) projects about 43 million tonnes of blade waste globally by 2050. Current routes include cement-kiln co-processing (where glass fibre replaces raw materials), mechanical grinding and reuse in bridges or shelters. Siemens Gamesa launched a recyclable blade using a resin that can be dissolved to recover fibres in 2021, and Vestas and others are commercialising chemical recycling for existing epoxy blades. Germany, the Netherlands, Austria and Finland restrict blade landfilling.

Outlook

The IEA’s net-zero pathways require wind generation to grow several-fold by 2050, with offshore wind becoming a backbone of supply in Europe, China and East Asia. Turbines keep getting bigger, though Western manufacturers have slowed the race to ever-larger models to stabilise supply chains and margins. The hard problems are permitting times (often 5–10 years in Europe), grid connection queues, offshore port and vessel capacity, and maintaining profitability after the 2022–2023 cost shock. Floating wind, hybrid wind-plus-storage plants, grid-forming inverters that supply synthetic inertia, and wind-powered green hydrogen are where development is heading. For how wind compares with other sources on cost, emissions and land use, see the technology comparison and the solar power overview.