Global Underground Transmission Systems Market Outlook, 2031

Underground transmission systems carry high-voltage electricity through insulated cables buried in trenches, ducts or tunnels instead of on overhead towers. They are used in cities, densely populated areas, environmentally sensitive landscapes, river and road crossings, and increasingly for long-distance HVDC corridors where overhead lines face public opposition. The main components are high-voltage cables, most commonly with cross-linked polyethylene insulation, joints and terminations, cable sealing ends, duct banks, tunnels, cooling systems, monitoring systems and associated substations or converter stations. Underground AC cables are typically used at 66 to 400 kilovolts, with some at 500 kilovolts, while extruded HVDC cables have reached 525 kilovolts and higher for land and subsea links. Costs are typically several times higher than overhead lines per kilometre, but underground systems have a much smaller visual footprint and are less exposed to weather and wildfire. Major suppliers include Prysmian, Nexans, NKT, LS Cable and System, Sumitomo Electric, Furukawa Electric, Southwire, Taihan, ZTT, Hengtong and Brugg Cables. Manufacturing capacity and installation expertise determine competitiveness.

Demand is driven by urban grid reinforcement, connection of offshore wind landing points, interconnectors, wildfire risk reduction and public acceptance requirements. Between 2024 and 2026, the sector saw strong order intake and capacity expansion: Prysmian completed its acquisition of United States wire maker Encore Wire in July 2024, Germany's SuedLink HVDC corridor, which runs mostly underground, received further planning approvals in May 2025, and New York's 1,250 megawatt Champlain Hudson Power Express, the longest fully buried transmission line in North America at 339 miles, was completed in June 2026. Policy in Europe and the United Kingdom, including the European Grids Package and RIIO-3, supports continued grid investment. However, long manufacturing lead times, limited installation capacity, high costs and complex repair procedures remain challenges. Through 2031, key variables are cable factory expansions, HVDC adoption, urban load growth, wildfire mitigation policy and cost reduction in installation methods. Suppliers with secured capacity and strong project execution are expected to hold an advantage.

Drivers •Urban Load Growth and Space Constraints in Cities Growing electricity demand in cities from data centres, electric vehicle charging, heat pumps and new developments requires new high-voltage supply points, and overhead lines are rarely feasible in dense urban areas. Underground cables allow utilities to reinforce city networks, connect new substations and replace ageing oil-filled cables. Data centre clusters near metropolitan areas often need dedicated underground connections. Urban redevelopment projects also require relocation of existing lines underground. Demand is strong.

•Public Acceptance, Environmental Protection and Resilience Underground cables reduce visual impact, protect landscapes and are less exposed to storms, ice, lightning and wildfire. Several countries, including Germany for its major HVDC corridors, have given priority to underground solutions to overcome opposition and speed approvals. Utilities in wildfire-prone regions are undergrounding lines in high-risk areas. Underground routes along roads, railways and existing corridors can simplify land access. Policy support is growing. Growth is solid.

Challenges •High Capital Cost and Complex Installation Underground transmission costs several times more than overhead lines per kilometre because of cable costs, civil works, trenching, horizontal drilling, tunnels and joint bays. AC cables also need reactive compensation over longer distances, which adds equipment cost. Installation is slow in urban areas because of traffic management, existing utilities and permitting for road works. Cost allocation to customers can be controversial when undergrounding is chosen for visual reasons. Budgets are tight. Regulators scrutinise costs.



•Manufacturing Bottlenecks, Long Lead Times and Repair Challenges Demand for high-voltage cables from offshore wind, interconnectors and onshore projects has filled factory order books for several years, and new extrusion lines and testing facilities take years to build. Specialised jointing technicians are scarce. When faults occur, locating and repairing underground cables can take weeks, which affects reliability planning and requires redundancy. Supply of raw materials such as copper, aluminium, lead and insulation compounds can be volatile. Delivery slots are limited. Schedules can slip.

Trends •Growth of Extruded HVDC Cable Systems for Long Land Corridors Extruded HVDC cables at 320 to 525 kilovolts are increasingly used for long onshore corridors and combined land and subsea links because they can carry several gigawatts with no reactive power limits. Germany's SuedLink and other corridors, as well as North American projects such as Champlain Hudson Power Express, demonstrate the approach. Manufacturers are developing higher voltage ratings and qualification for 525 kilovolt and above. Standardisation of HVDC cable designs is being discussed to speed procurement. Adoption is rising.

•Capacity Expansion, Digital Monitoring and Lower-Carbon Cables Cable makers are expanding factories in Europe, North America and Asia and signing long-term reservation agreements with system operators. Distributed temperature sensing, partial discharge monitoring and digital twins are being used to optimise cable loading and detect faults early. Producers are increasing recycled content, reducing lead use and offering low-carbon aluminium and copper. Trenchless installation methods and improved jointing techniques help cut installation time. Customers increasingly request carbon footprint data. Interest is growing.

High voltage cables from 66 to 220 kilovolts lead because they make up most urban transmission networks, while extra high voltage and HVDC cables grow fastest through long corridors and interconnectors. High voltage underground cables from 66 to 220 kilovolts are the largest voltage segment because they are widely used for urban transmission, substation connections, renewable project connections and replacement of older oil-filled cables in cities around the world. These cables are produced by many manufacturers and installed by regional contractors. Extra high voltage AC cables at 275 to 500 kilovolts are used for major urban supply points and short critical sections of transmission routes. HVDC cables at 320 to 525 kilovolts are the fastest growing segment because they enable long land corridors and combined land and subsea links that can carry several gigawatts, as seen in Germany, the United Kingdom, North America and Asia. Through 2031, HVDC and extra high voltage cables are expected to grow faster than the total, while 66 to 220 kilovolt cables remain the largest by length.

XLPE-insulated cables lead because they are lighter, easier to install and maintain than older technologies, while gas-insulated lines remain a niche for very high capacity short routes. Cross-linked polyethylene insulated cables are the dominant cable type because they offer good electrical performance, lower maintenance, no fluid leakage risk and simpler jointing than older oil-filled or paper-insulated cables, and they are now used up to 500 kilovolts AC and 525 kilovolts DC. Mass-impregnated paper cables are still used for some HVDC subsea links. Oil-filled and high-pressure fluid-filled cables are being replaced gradually in older urban networks because of leakage risk and maintenance needs, which creates replacement demand. Gas-insulated transmission lines are used for very high capacity short sections, tunnels and substations. Superconducting cables are in demonstration for high-density urban areas. Through 2031, XLPE cables are expected to continue gaining share, while replacement of fluid-filled cables supports demand in North America, Europe and Japan.

Cables lead spending because they are the largest material cost, while civil works and monitoring systems grow as projects become longer and more complex. Cables account for the largest share of spending in underground transmission projects because high-voltage conductors, insulation and metallic sheaths are costly and require specialised production and testing. Accessories, including joints, terminations and sealing ends, are critical for reliability and require skilled installation. Civil works, including trenching, duct banks, horizontal directional drilling and tunnels, form a large share of total cost, especially in cities. Converter stations are required for HVDC links. Monitoring systems, including distributed temperature sensing, partial discharge detection and sheath current monitoring, are the fastest growing component as operators seek to maximise loading and detect faults. Installation and engineering services are essential. Through 2031, monitoring and HVDC-related components are expected to grow faster than the total.

Utility and grid reinforcement projects lead because urban networks need continuous upgrading, while interconnectors and renewable connections grow fastest through offshore wind and cross-border trade. Utility and grid reinforcement projects are the largest application because transmission owners in cities across North America, Europe and Asia are reinforcing supply to growing urban loads, replacing ageing cables and connecting new substations. Interconnectors and long-distance HVDC corridors are the fastest growing application, as countries link grids and build long underground routes where overhead lines are not acceptable. Renewable connections, including onshore cable routes from offshore wind landing points and solar parks, are a large and growing application. Industrial and data centre connections require dedicated cables for large loads. Undergrounding for wildfire mitigation and resilience is an emerging application in parts of the United States. Through 2031, interconnectors and renewable connections are expected to grow faster than utility reinforcement.

Europe leads underground transmission through HVDC corridors, offshore wind connections and urban cable networks, Asia-Pacific grows fastest through dense urban grids and interconnectors, and North America expands through urban reinforcement, buried HVDC lines and wildfire mitigation. North America is a growing region for underground transmission, driven by urban reinforcement in cities such as New York, Chicago, Los Angeles and Toronto, replacement of ageing fluid-filled cables, data centre connections and buried HVDC lines. The Champlain Hudson Power Express, a 339 mile, 1,250 megawatt buried HVDC line bringing Canadian hydropower to New York City, was completed in June 2026. Prysmian's acquisition of Encore Wire in July 2024 strengthened its North American presence, and cable makers are expanding United States production. Utilities in California and other wildfire-prone states are undergrounding some lines in high-risk areas, although cost limits the scale. Regulators review the cost of undergrounding against overhead alternatives. Transmission planning under Order No. 1920 may increase interregional projects that include underground sections. By 2031, growth is expected from urban reinforcement, buried HVDC links, data centre connections and cable replacement programmes.

Europe is the leading region for underground transmission, supported by strong policy for underground HVDC corridors, offshore wind connections and dense urban networks. Germany decided to build major north-south HVDC corridors such as SuedLink mostly underground, and the regulator approved further sections in May 2025. The Netherlands, Denmark, Belgium and the United Kingdom are building onshore cable routes from offshore wind landing points and interconnectors. The United Kingdom's RIIO-3 settlement, published in December 2025, and the European Grids Package of December 2025 support continued investment. European cable makers Prysmian, Nexans and NKT have expanded factories and signed capacity reservation agreements with system operators. Urban networks in London, Paris, Berlin and other cities continue to replace older cables. By 2031, growth is expected from HVDC corridors, offshore connections and urban reinforcement, though cable supply and installation capacity remain bottlenecks.

Asia-Pacific is the fastest growing region. Japan, South Korea, Singapore, Hong Kong and major Chinese cities have dense underground transmission networks and continue to add cables to serve urban growth. China is building underground and subsea cables for city networks and offshore wind, supported by large domestic manufacturers. South Korea is planning HVDC links, including underground sections, to carry power from coastal plants and offshore wind to the capital region. India is increasing underground cabling in large cities such as Delhi, Mumbai and Bengaluru, where overhead corridors are not available. Australia is assessing undergrounding for some new transmission routes in response to community concerns. Singapore has built deep cable tunnels for its transmission network. By 2031, the region is expected to account for a large share of new underground cable length, with local manufacturers increasing high-voltage capability.

Latin America is a smaller region for underground transmission, with demand concentrated in large cities such as São Paulo, Rio de Janeiro, Mexico City, Santiago, Bogotá and Buenos Aires, where utilities need to reinforce urban networks and connect new substations. Most long-distance transmission remains overhead because of lower costs and long distances. Brazil's transmission auctions include some underground urban sections, and Chile and Colombia are investing in urban cable projects. Offshore wind and interconnection projects are at early stages. Barriers include high costs, limited local manufacturing of high-voltage cables, financing and currency risk. Cable supply comes mainly from European and Asian manufacturers. By 2031, growth is expected from urban reinforcement and data centre connections, with some underground sections in new corridors through sensitive areas.

The Middle East and Africa are developing regions for underground transmission, with demand concentrated in large Gulf cities, new urban developments and industrial zones. The United Arab Emirates, Saudi Arabia, Qatar and Kuwait use underground cables widely in urban networks, and Saudi giga-projects and new cities include extensive underground infrastructure. Gulf countries are also developing subsea interconnections. Egypt is reinforcing urban networks in Cairo and new administrative areas. South Africa uses underground cables in major cities, and other African countries are adding cables mainly in capital cities. Barriers include high costs, extreme heat that affects cable rating, limited local manufacturing and financing constraints in parts of Africa. By 2031, growth is expected from Gulf urban development, giga-projects and interconnectors, with local cable production expanding in the region.

June 2026 – Champlain Hudson Power Express completed in New York: The 339 mile, 1,250 megawatt HVDC line, buried underground and underwater, became the longest fully buried transmission line in North America.

December 2025 – European Commission publishes the European Grids Package: The package proposes faster permitting and more coordinated EU-wide network planning, supporting investment in cable corridors and interconnectors.

December 2025 – Ofgem publishes RIIO-3 final determinations: The regulator approved an initial 10.3 billion pounds for electricity transmission for its new five-year price control period, supporting continued underground and onshore cable projects in Great Britain.

May 2025 – Germany approves further SuedLink sections: The Federal Network Agency completed planning approval for additional sections of the mostly underground HVDC corridor, allowing transmission operators to proceed with construction.

July 2024 – Prysmian completes acquisition of Encore Wire: Prysmian acquired the United States wire and cable maker for 290 dollars per share in cash, strengthening its North American manufacturing base for power cables.


Considered in this report
• Historic Year: 2020
• Base Year: 2025
• Estimated Year: 2026
• Forecast Year: 2031

Aspects covered in this report
• Global Underground Transmission Systems Market with its segments and regional outlook
• Various drivers and challenges
• Ongoing trends and developments
• Key developments and regulatory milestones

By Voltage Level
• •66 to 220 kilovolt
• •275 to 500 kilovolt AC
• •HVDC (320 to 525 kilovolt)

By Cable Type
• •XLPE cables
• •Mass-impregnated cables
• •Oil-filled and fluid-filled cables
• •Gas-insulated lines

By Component
• •Cables
• •Joints and terminations
• •Civil works and tunnels
• •Monitoring systems
• •Installation and engineering services

By Application
• •Utility and urban grid reinforcement
• •Interconnectors and HVDC corridors
• •Renewable energy connections
• •Industrial and data centre connections
• •Wildfire mitigation and resilience