Offshore wind is normally argued about as an environmental, economic or energy question. Supporters point to renewable electricity and reduced dependence upon fossil fuels; opponents point to cost, intermittency, transmission infrastructure, marine impacts and the industrialisation of coastlines. There is another question that receives considerably less public attention: what happens when hundreds of enormous moving structures are placed precisely where a modern state needs its sensors to see?
The answer is sufficiently serious that the British Ministry of Defence and the United States Department of Defense have spent years trying to solve the problem. Wind turbines can interfere with radar. This is not speculation from opponents of renewable energy. The U.S. Department of Energy states explicitly that land-based and offshore turbines within radar line of sight can impede radar systems used for air traffic control, weather forecasting, homeland security and national defence. The towers and rotating blades reflect electromagnetic radiation, producing clutter, reducing detection sensitivity and complicating the identification and tracking of genuine airborne targets.
Britain has been even more explicit about the defence implications. The Ministry of Defence has acknowledged that offshore wind farms can adversely affect the long-range Primary Surveillance Radars forming the backbone of British air defence. Degradation of those radars can reduce the range and time available to identify and respond to a potential aggressor. The MOD's own assessment described such degradation as unacceptable for national security.
That immediately disposes of the simplistic answer that concern about offshore wind and defence is merely another anti-renewables scare story. There is a real problem. The more difficult question is whether it is a manageable engineering problem or a strategic reason to restrict offshore wind development.
Radar works by transmitting electromagnetic energy and analysing what comes back. A wind turbine is hardly an inconspicuous object. Modern offshore turbines can be immense, with blades sweeping through a large area at considerable speed. Radar therefore encounters both a substantial stationary structure and rapidly moving components. The resulting returns can resemble movement, create clutter and make the radar's task of separating genuine aircraft from environmental background more difficult. The problem can become particularly important when many turbines are concentrated together in large offshore arrays.
This matters because the sea is not merely empty space conveniently available for electricity generation. For an island such as Britain, it is part of the country's defensive approaches. For continental countries with long coastlines, including Australia, maritime approaches are similarly important for surveillance. Aircraft, missiles, drones, ships and submarines do not politely approach through locations chosen to make the defender's sensors effective.
The radar problem also illustrates an important asymmetry between civilian planning and military planning. Civilian infrastructure is normally designed around expected conditions. Defence must worry about an adversary deliberately exploiting weaknesses. A radar anomaly that is merely inconvenient during peacetime becomes much more significant if an enemy knows exactly where the interference occurs and plans accordingly.
This does not mean that a wind farm creates some magical invisible corridor through which hostile aircraft can fly undetected. That would exaggerate what the evidence establishes. Radar interference varies according to the radar, turbine design, geography, distance, atmospheric conditions and layout of the wind farm, and governments can employ multiple sensors and mitigation technologies. The correct defence question is therefore not whether turbines make aircraft invisible, but whether they degrade detection sufficiently to create operational vulnerabilities.
The seriousness with which Britain has treated the issue is instructive. The MOD established programmes with the offshore wind industry specifically to find technologies capable of maintaining air-defence surveillance as increasingly large turbines and wind farms were constructed. Its 2022 assessment said the detrimental impact upon air-defence radar was already well documented and could worsen with the increased size and scale of future developments.
Britain has now gone considerably further. In March 2026 the government announced the purchase of specially designed air-defence radars intended to mitigate the anomalies created by offshore wind farms and thereby permit another 10 GW of offshore wind development. The new systems are expected to begin installation from 2029. The British government presents this as a coexistence solution: retain offshore wind while upgrading the radar network sufficiently to preserve air-defence capability.
That solution is not free. In July 2026 the British government disclosed that it had signed a £95 million contract with BAE Systems for the advanced radar system needed to secure coexistence between offshore wind and air defence. The expenditure itself is revealing. Governments do not spend £95 million replacing military radar to solve an imaginary problem.
The American response is similar. The U.S. Department of Defense, Department of Energy, Department of Homeland Security, Federal Aviation Administration, NOAA and other agencies have cooperated on wind-turbine radar interference for years. Their 2023 strategy acknowledges that as wind development expands, conflicts with critical radar missions are likely to increase and potentially become more severe. The response is improved assessment, hardware and software mitigation, and development of future radar systems more resistant to turbine interference.
This gives the issue a rather different complexion from the usual political argument. The serious position is neither that offshore wind presents no defence problem nor that every offshore turbine constitutes a threat to national security. Defence agencies themselves occupy the ground between those positions: the interference is real, but engineering, careful siting and improved radar may permit coexistence.
Australia should pay particular attention because surveillance is central to Australian defence strategy. Geography gives Australia enormous strategic depth, but that advantage depends upon knowing what is approaching across that geography. Australia's Jindalee Operational Radar Network is sufficiently important that the government describes its over-the-horizon radar technology as world-leading and in June 2026 signed a $2.5 billion agreement to supply related technology to Canada.
Australian Defence has also been involved directly in consultation over proposed offshore renewable areas. Documents concerning the Illawarra offshore renewable zone show Defence assessing the proposal and requiring continued involvement with individual wind-farm projects and the technologies employed. Parts of the released Defence assessment were withheld on national-security and other statutory grounds, which itself demonstrates why public debate cannot expect every operational concern to be disclosed in detail.
That creates a problem for democratic decision-making. The public may be shown an environmental-impact statement describing whales, seabirds, fisheries, visual amenity and electricity generation while some of the most important defence assessments cannot sensibly be published in full. A potential adversary does not need a government report explaining exactly which sensor performs less effectively from which bearing under which circumstances.
The sensible principle should therefore be that Defence has an effective veto where an offshore development would create an inadequately mitigated degradation of essential surveillance. Britain already operates along these lines. The British government stated in 2026 that an offshore wind farm capable of affecting air-defence radar would only be approved once appropriate safeguards were firmly in place.
There is another defence issue beyond radar: concentration of critical energy infrastructure at sea. A country that becomes increasingly dependent upon offshore electricity generation is placing a growing proportion of its energy system in physically exposed locations. Turbines, offshore substations, undersea cables and grid connections are large pieces of infrastructure whose locations cannot be concealed.
This is not necessarily an argument against offshore wind. Oil platforms, gas pipelines, electricity interconnectors and submarine telecommunications cables are vulnerable too. Modern societies already depend upon exposed infrastructure. It does mean that energy planners should stop treating national security as something separate from energy policy.
The sabotage of the Nord Stream pipelines provided a spectacular reminder that infrastructure sitting on the seabed can become part of geopolitical conflict. Submarine communications cables have similarly become an increasing security concern. An offshore electricity system therefore requires surveillance, redundancy, repair capacity and physical and cyber protection appropriate to infrastructure upon which a modern economy may depend.
Cybersecurity adds another dimension. Modern wind farms are not nineteenth-century windmills mechanically connected to generators. They are digitally monitored industrial systems incorporating sensors, communications equipment, power electronics and remote-management systems. The relevant defence question therefore includes not merely who manufactures the tower and blades, but who supplies the software, communications hardware and control systems and who can access them remotely.
That question becomes particularly uncomfortable when renewable-energy supply chains intersect with strategic dependence upon China. Britain is already debating the national-security implications of Chinese-linked ownership and equipment in its offshore wind sector, including concerns about supply dependence and possible remote technological interference. Those allegations require project-specific evidence rather than general suspicion, but the strategic principle is elementary: critical energy infrastructure should not contain remotely controllable systems whose security cannot be independently verified.
There is also a wartime question rarely raised in the cheerful language of renewable-energy targets. What happens to an offshore wind farm during a serious military conflict?
A large turbine is not difficult to locate. Neither is an offshore substation. Cables eventually converge upon identifiable landing points. An adversary would not necessarily need to destroy hundreds of turbines individually. Depending upon the architecture of the system, disabling substations, transmission connections, control systems or cable routes could potentially remove substantial generating capacity.
Once again, this is not unique to wind. A conventional power station is also an obvious target, while pipelines and LNG terminals present their own vulnerabilities. The relevant comparison is therefore resilience rather than invulnerability. Distributed generation can sometimes improve resilience precisely because it avoids dependence upon a handful of enormous power stations, but offshore systems can simultaneously create new concentrations at substations, export cables and grid connections.
Defence planning consequently needs to be embedded at the design stage rather than added after construction. Where will the turbines sit relative to radar? What mitigation is required? Who pays for replacement radar if a private development necessitates it? How many export cables are there? How rapidly can damaged cables be repaired? Are spare transformers and critical components available domestically? Can the wind farm operate if international communications are interrupted? Who controls its software? Can remote foreign access be physically disabled?
The question of who pays deserves particular attention. Britain is spending £95 million on advanced radar partly because expanding offshore wind would otherwise interfere with existing air-defence surveillance. One can reasonably ask why taxpayers rather than the developments creating the interference should ultimately bear that cost. If construction of a private energy project requires modification of national defence infrastructure, the cost belongs in the economic calculation of the project rather than disappearing into another government department's budget.
This is the same principle that should govern grid connections, transmission lines and other external costs. A technology should compete after its system costs are counted, not after inconvenient costs have been transferred to somebody else's balance sheet.
The mistake is therefore to allow climate or renewable-energy targets to acquire automatic priority over defence considerations. Megawatts are not strategically neutral. Energy infrastructure exists within geography, communications networks, supply chains and military surveillance systems.
The revealing fact is that defence ministries already understand this. Britain has spent years developing radar mitigation and is now buying replacement systems. The United States operates an interagency programme involving defence, homeland security, aviation and energy agencies. Australian Defence participates in offshore renewable planning because it knows that the location and technology of these developments can intersect with defence requirements.
The proper test for an offshore wind farm is consequently broader than how much electricity it generates. Does it degrade radar? If so, can that degradation be completely and independently mitigated? Who pays for the mitigation? Does the project create new vulnerabilities in electricity transmission? Are critical components and software secure? Is foreign ownership strategically acceptable? Can the infrastructure be repaired rapidly after sabotage or military attack? Does Defence retain the ability to object where an unresolved operational risk remains?
The sea surrounding a nation is not vacant industrial real estate. It is an energy resource, an ecological environment, a commercial highway and a defensive approach. Offshore wind may have a legitimate place within it, but electricity policy does not outrank national survival.
https://www.spectator.com.au/2026/09/is-offshore-wind-a-defence-risk/