High-voltage direct current (HVDC) transmission has become the backbone of long-distance power transfer, enabling efficient delivery of renewable energy from offshore wind farms and remote generation sites to demand centers. Submarine interconnectors like NordLink and the North Sea Link exemplify how cross-border grids are being tied together, while cable specialists such as Prysmian, Nexans, and NKT secure multi-billion-euro order books. This article explores the world’s longest HVDC projects, cost dynamics, and the key listed companies driving the expansion.
TL;DR
- HVDC transmission lines enable long-distance, low-loss electricity transfer.
- Submarine interconnectors link offshore wind and cross-border grids.
- Longest projects include Itaipu (Brazil), Xiangjiaba–Shanghai (China), and NordLink (Norway–Germany).
- Key listed cable suppliers: Prysmian (BIT: PRY), Nexans (EPA: NEX), NKT (CPH: NKT).
- Submarine HVDC cables typically cost €2–5m per km, depending on depth and complexity.
Why HVDC Transmission Lines Matter
As electricity demand rises and renewable generation moves offshore or into remote areas, HVDC lines are increasingly used:
- Overhead lines: Transfer bulk power across continents.
- Submarine cables: Connect offshore wind farms and cross-border grids.
- Hybrid solutions: Combine overhead and subsea for flexibility.
HVDC is more efficient than AC when distances exceed ~600 km overhead or ~50 km subsea.
The Longest HVDC Transmission Lines (2025)
| Project / Line | Capacity (MW) | Length (km) | Region | Notes |
|---|---|---|---|---|
| Xiangjiaba–Shanghai | 6,400 | 2,071 | China | World’s longest HVDC line |
| Itaipu HVDC | 6,300 | 800 | Brazil–Paraguay | Landmark bi-national project |
| Ultranet (Germany) | 2,000 | 340 | Germany | Under construction |
| SunZia (US Southwest) | 3,000 | ~885 | US | Unlocks renewable capacity |
| Pugalur–Trichur | 2,000 | 165 | India | Commissioned 2021 |
The Longest HVDC Submarine Cables (2025)
| Interconnector | Capacity (MW) | Length (km) | Region | Companies Involved |
|---|---|---|---|---|
| North Sea Link | 1,400 | 720 | Norway–UK | Prysmian, Siemens Energy |
| NordLink | 1,400 | 623 | Norway–Germany | Nexans, ABB/Hitachi |
| Greenlink | 500 | 190 | UK–Ireland | Nexans, Siemens Energy |
| IFA2 | 1,000 | 200 | UK–France | Nexans, GE Vernova |
| ADNOC Offshore HVDC | 3,200 | 140 | UAE | Hitachi, KEPCO |
Cost of HVDC Submarine Cables
- Typical cost range: €2–5 million per km, depending on seabed geology, installation depth, and protection requirements.
- Converter stations: Add another €300–600 million per terminal.
- Project scale: A 500 km, 1 GW interconnector can exceed €2–3 billion in total cost.
Costs are trending higher due to supply chain bottlenecks, rising copper prices, and offshore construction inflation.
Key Listed Cable Companies
Prysmian (BIT: PRY)
- Market leader in submarine HVDC cables.
- Key projects: North Sea Link, Soo Green HVDC Link.
- Strong orderbook visibility through 2030.
Nexans (EPA: NEX)
- French cable manufacturer with deep subsea expertise.
- Active in NordLink, Greenlink, IFA2.
- Positioning in offshore wind HVDC hubs.
NKT (CPH: NKT)
- Denmark-based, specialist in HVDC cables.
- Benefiting from European interconnector expansion.
Investor Note: Cable makers are capacity-constrained; orderbook growth provides strong earnings visibility but execution risks remain.
FAQ
Q: What is the longest HVDC transmission line in the world?
China’s Xiangjiaba–Shanghai project at over 2,000 km is the longest HVDC line globally.
Q: Which is the longest HVDC submarine cable?
The North Sea Link between Norway and the UK (720 km) is the world’s longest subsea HVDC interconnector.
Q: How much does an HVDC submarine cable cost per km?
Typical installation costs range from €2–5 million per km, depending on conditions.
Q: Which companies dominate HVDC cable manufacturing?
Prysmian, Nexans, and NKT are the top listed players, with Prysmian holding the largest global market share.