HVDC links: Efficiency and losses
Why DC beats AC on long hauls and under the sea
What this tab covers How much energy is lost while it moves and while it waits in storage or transit, and how much energy the transport itself consumes, in per cent.A 2,000 km ±800 kV UHVDC link loses about 7% of its power end to end, roughly 3.5% per 1,000 km including converters. Each converter station accounts for about 0.7 to 1%, so on short links the converters dominate.
Chart: Efficiency ranges
Whole chain Lost in transitLosses by measure
| Measure | Range | Type | What is measured |
|---|---|---|---|
| Whole-link losses, ±800 kV Xiangjiaba to Shanghai | 7%3 | Whole chain | Total losses over about 2,000 km (about 3.5% per 1,000 km, calculated), versus 10% for a conventional ±500 kV DC line |
| Line losses only, same link | 2.7%34 | Lost in transit | Per 1,000 km of line, calculated by subtracting about 0.8% per converter station from the 7% total over 1,980 km of line |
| Converter losses, LCC | 0.7 to 0.8%45 | Lost in transit | Share of power lost in one converter station at rated power |
| Converter losses, VSC (modular multilevel) | 0.8 to 1%45 | Lost in transit | Share of power lost in one converter station; older two-level VSC designs lost about 2 to 3% |
| ±1,100 kV UHVDC versus conventional systems | 40% lower (up to)1 | Lost in transit | Losses of the Changji to Guquan link compared with a conventional transmission system (manufacturer figure) |
Holding periods and inventory
| Measure | Value |
|---|---|
| Time in transit | About 10 milliseconds over 3,000 km (calculated); no stored inventory in the line |
| Economic break-even with AC | About 300 miles (about 480 km) for overhead lines and about 30 miles (about 50 km) for cables (EPRI)4 |
Converter losses are roughly fixed per station, while line losses grow with distance, so HVDC pays off only once the line-loss saving over distance outweighs the two converter stations. That is why HVDC dominates long overhead routes and subsea links but not short land routes.
No fuel is burned to drive HVDC: the energy cost is the losses, which include cooling of the converter valves. Utilisation can be high on dedicated links: Changji to Guquan was designed to deliver about 66 TWh a year, about 63% of its maximum (calculated).
Sources
- The world's most powerful transmission system facilitated by Hitachi ABB Power Grids Hitachi Energy, 2020
- Xiangjiaba - Shanghai (case study) Hitachi Energy, 2024
- Overview of HVDC Technologies and EPRI's HVDC Research (R. Adapa, presentation to ERCOT) EPRI / ERCOT, 2023
- Market Integration of HVDC Lines: Internalizing HVDC Losses in Market Clearing (Tosatto, Weckesser, Chatzivasileiadis) arXiv (Technical University of Denmark), 2018