Installing a wind turbine is a multi-stage construction project that can take anywhere from a few months for a single onshore turbine to over two years for a large offshore wind farm. The process involves building a foundation, transporting massive components to the site, assembling the tower and rotor, wiring everything into the electrical grid, and running extensive tests before the turbine generates its first commercial kilowatt.
Building the Foundation
Every wind turbine starts with a foundation engineered for the specific site conditions. Onshore turbines typically sit on reinforced concrete foundations poured into excavated pits. These foundations can be 15 to 20 meters across and several meters deep, with steel rebar cages and anchor bolts set into the concrete to receive the base of the tower. Once poured, the concrete needs several weeks to cure before it can support the structure above.
Offshore installations are more complex and use different foundation types depending on water depth. In shallow waters up to about 30 meters, monopile foundations are the most common. These are single steel cylinders, sometimes 8 meters in diameter, driven directly into the seabed by hydraulic hammers. Gravity-base foundations, also used in shallow water, are massive steel or concrete structures heavy enough to sit on the seabed without being anchored. For transitional depths of 20 to 80 meters, jacket foundations provide more stability through a lattice framework with three or four anchoring points driven into the seafloor, similar to the structures used in oil and gas platforms.
Transporting the Components
Modern wind turbine components are enormous, and moving them from the factory to the installation site is a logistical challenge in itself. A mid-range turbine like the Vestas V90 has a nacelle (the housing that sits atop the tower containing the generator and gearbox) weighing 75 tons, three blades measuring 62 meters each at 40 tons apiece, and tower sections totaling 152 tons. The entire structure adds up to roughly 267 tons. Larger turbines dwarf even those numbers. Siemens has developed offshore models rated at 15 megawatts with rotor diameters reaching 222 meters, meaning each blade stretches longer than a football field.
Getting these parts to the site requires specialized transport. Blades travel on extendable trailers that can stretch beyond 70 meters, often requiring escort vehicles, road closures, and careful route planning to navigate turns, bridges, and overpasses. Nacelles are so large that transporting them on public roads requires special permits and custom-engineered vehicles. Tower sections, typically shipped in two or three cylindrical segments, travel on heavy-haul flatbed trucks. For offshore projects, components are loaded onto purpose-built installation vessels equipped with cranes capable of lifting hundreds of tons at height.
Assembling the Tower and Rotor
Once components arrive on site, assembly follows a bottom-up sequence. Crawler cranes (onshore) or jack-up vessels (offshore) handle the heavy lifting. The first tower section is bolted to the foundation’s anchor ring, followed by the second and sometimes third section stacked on top. Each connection point is torqued to precise specifications.
The nacelle goes up next, hoisted to the top of the completed tower and secured in place. This is one of the most delicate lifts of the entire project because the nacelle contains the generator, gearbox, control systems, and yaw mechanism that allows the turbine to rotate and face the wind. Weather windows matter enormously here. High winds, which ironically are common at good turbine sites, can halt crane operations entirely. Crews often work in the early morning hours when winds tend to be calmest.
Blade installation is the final and most weather-sensitive step. Each blade is either lifted individually and bolted to the rotor hub already mounted on the nacelle, or all three blades are pre-assembled into a full rotor on the ground and hoisted as a single unit. Individual blade lifts are more common because they require smaller cranes and are easier to control in light wind. The blade’s aerodynamic shape makes it act like a sail during the lift, so even moderate gusts can make positioning dangerous.
Connecting to the Electrical Grid
A turbine generates electricity at a relatively low voltage, typically around 690 volts. A transformer at the base of each tower steps that up to 25 to 40 kilovolts for the collection system, which is the internal cable network linking all the turbines in a wind farm together. These medium-voltage cables, buried underground onshore or laid along the seabed offshore, carry power from each turbine to a central substation.
At the substation, larger transformers step the voltage up again, usually to 132 to 150 kilovolts, for transmission to the main power grid. Offshore wind farms require an offshore substation platform, which is essentially a small industrial building on stilts in the ocean, connected to shore by high-voltage submarine cables. The entire electrical path includes power electronic converters that condition the variable-frequency output of the turbine’s generator into the stable frequency the grid requires.
Commissioning and Performance Testing
Before a turbine enters commercial service, it goes through a rigorous commissioning process. Individual turbine tests begin with a six-hour run while connected to the grid, during which crews verify that vibration levels stay within acceptable limits, the yaw drives (which point the turbine into the wind) function correctly, and the power measurement system reads accurately. Safety-critical functions are tested explicitly: what happens during a sudden grid loss while generating, whether the overspeed trip shuts the turbine down if the rotor spins too fast, and whether all electrical protection relays are set correctly.
After passing those initial checks, each turbine must run continuously for 240 hours, with at least 150 of those hours actively producing power to the grid. During that window, no more than three faults caused by the turbine itself are allowed, and no faults at all are permitted in the final 100 hours. This extended test catches intermittent problems that a short run might miss.
The entire wind farm then undergoes its own 200-hour completion test, requiring at least 150 hours of active generation and a minimum 85% availability across all turbines. Transformer temperatures are measured under high load to confirm the electrical infrastructure can handle peak output. Foundation conductivity tests verify that the grounding system works properly, ensuring both equipment protection and crew safety. Only after all of these milestones are met does the wind farm begin commercial operations.
What It Costs
The total installed cost for a land-based wind project runs about $1,200 to $1,800 per kilowatt of capacity, according to U.S. Department of Energy market reports. That means a typical 3-megawatt onshore turbine costs roughly $3.6 to $5.4 million fully installed, covering everything from the foundation to grid connection. Offshore wind is significantly more expensive at $3,500 to $4,000 per kilowatt, driven by the cost of marine foundations, specialized installation vessels, and submarine cabling. A 500-megawatt offshore wind farm can easily exceed $2 billion in total capital expenditure.
The installation phase itself, distinct from manufacturing the components, represents a meaningful share of these costs. Crane rental, specialized vessels, skilled labor, and the sheer logistical complexity of coordinating oversized transport all add up. Offshore projects face additional cost pressure from weather delays, since jack-up vessels and crew transfer boats can only operate in certain sea states, and every day a vessel sits idle costs tens of thousands of dollars.