Finding
China has built a DC grid; the US has just finished its first long lines in a decade
By late 2025 China had more than 40,000 km of ultra-high-voltage DC lines in service: 23 lines at 800 kV and one at 1,100 kV, the 3,293 km Changji-Guquan link that carries 12 GW from Xinjiang to Anhui. State Grid plans 15 more UHV lines from 2026 to 2030. In the US, two long HVDC lines entered service in 2026: SunZia (about 550 miles, 3 GW, New Mexico wind to Arizona) and Champlain Hudson Power Express (339 miles, 1.25 GW, fully buried, Quebec hydro to New York City).
The difference is not technology; both US lines use the same converter makers China once bought from. It is permitting and cost allocation. Grain Belt Express, an 800-mile, 5 GW line from Kansas to Indiana first proposed in 2010, is still clearing land and grid-operator approvals. HVDC moves power across state lines, and US rules make every state along the route a veto point.
For the rest of electrification, DC matters at both ends. Converter stations use the same IGBT and silicon carbide devices as EV inverters and battery storage, and the same three Western makers - Hitachi Energy, Siemens Energy and GE Vernova - supply both HVDC terminals and the transformers already in short supply.
When DC wins
HVDC vs AC transmission
| Factor | AC | DC |
|---|---|---|
| Distance | Losses grow with reactive current; practical limit ~800 km overhead | Wins above ~600-800 km overhead and ~50-80 km subsea or underground |
| Cable | Charging current limits AC cable to tens of km | No length limit; links routinely exceed 500 km |
| Grids | Both ends must be synchronized | Joins grids at different frequencies or phases |
| Control | Flow follows impedance | Flow set and reversed in milliseconds |
| Footprint | Three conductors | Two conductors for the same power |
| Cost | No converter stations | Converter stations cost hundreds of millions of dollars each |
Converters
Two converter types
| Type | Switch | Strengths | Used for |
|---|---|---|---|
| Line-commutated (LCC) | Thyristors | Up to ~12 GW per bipole; lowest losses at bulk scale | Needs strong AC grids at both ends; most Chinese UHVDC |
| Voltage-source (VSC) | IGBT; SiC in development | ~2-3 GW per bipole; grid-forming, black start, reverses flow | All offshore wind, SunZia, CHPE, meshed DC grids |
Projects
Major HVDC lines
| Project | Where | Capacity | Line | Status |
|---|---|---|---|---|
| Changji-Guquan | China | 12 GW | 3,293 km; 1,100 kV | In service since 2019 |
| SunZia | US (NM-AZ) | 3 GW | ~550 mi; 525 kV VSC | In service 2026 |
| Champlain Hudson Power Express | US (QC-NY) | 1.25 GW | 339 mi, buried | In service June 2026 |
| Grain Belt Express | US (KS-IN) | 5 GW | ~800 mi; 600 kV | Permitting and land acquisition |
| TransWest Express | US (WY-NV) | 3 GW | ~730 mi | Development |
| Southern Spirit | US (TX-MS) | 3 GW | ~320 mi; links ERCOT to the Southeast | Development |
| Dogger Bank | UK offshore | 3.6 GW | 320 kV VSC export | Phased; final phase under construction |
| North Sea offshore grid | EU and UK | Tens of GW planned | Multi-terminal VSC | Several links under construction |
Suppliers
Who builds converter stations
Converter transformers and HV cable are the long-lead items; see the Grid Equipment Supply Chain.
| Company | Origin | Scope |
|---|---|---|
| Hitachi Energy | Switzerland / Japan | LCC and VSC (HVDC Light); SunZia, CHPE |
| Siemens Energy | Germany | LCC and VSC (HVDC Plus); North Sea links |
| GE Vernova | USA / France | LCC and VSC; offshore wind links |
| NR Electric (NARI) | China | VSC and LCC for State Grid |
| XD Group | China | Converter valves and transformers for UHVDC |
| XJ Electric and TBEA | China | Valves, converter transformers |
MVDC
Medium-voltage DC at the site
Medium-voltage DC (roughly 1-35 kV) carries the same idea to the site: fewer AC-DC conversions between solar, batteries, chargers and DC loads.
- Data centers: 800 V DC rack power is moving from pilot to deployment; MVDC with solid-state transformers would feed it from the substation - see DatacentersX.
- Truck depots: megawatt chargers and on-site batteries share a DC bus behind one grid connection.
- Solar and storage plants: DC-coupled batteries skip an inverter stage.
- Ships, ports and mines: DC shipboard grids are already common.
Sources
Sources and scope
- Scope
- HVDC and MVDC transmission and distribution: technology, projects and suppliers
- Sources
- China National Energy Administration (via Hunan provincial government, November 2025); State Grid; WECC SunZia progress report 2026; project and press reporting
- Updated
- October 2026