China’s network of ultra-high-voltage (UHV) transmission lines is often described as a pillar of the country’s clean-energy transition. With relatively low losses, it can move power thousands of kilometres, from renewable energy megabases in the country’s north and west, to demand hotspots along the populous eastern seaboard.
But much of the electricity it carries still comes from coal. A system widely seen as essential for delivering clean power, now risks locking in fossil fuel.
With China set to invest roughly RMB 5 trillion yuan (over USD 700 billion) in its power grid by 2030, the next five years are a critical window to raise the renewable share on these UHV lines. The technology to do so exists – from storage to more flexible grid configurations – but the outcome will depend on whether policy frameworks in China shift to support its deployment.
Built for distance, not decarbonisation
No country has deployed UHV technology on a comparable scale to China. According to our research at Global Energy Monitor, by the end of 2025, the country had commissioned 45 UHV lines , totalling 52,300 km and with a transmission capacity of about 300 gigawatts (GW). This accounts for over 70% of China’s inter-regional and inter-provincial power-transmission capacity. UHV in more detail UHV transmission refers to alternating current (AC) lines operating at 1,000 kilovolts (kV) or higher and direct current (DC) lines at ±800 kV or above.
UHVDC is typically used for long-distance, point-to-point transmission, while UHVAC is better suited for interconnected networks.
Compared with conventional grids, UHV lines that operate at far higher voltages allow proportionally lower current which can dramatically reduce energy loss along the way. This physical feature enables UHV lines to transmit far larger volumes of power over long distances, especially UHVDC, with higher efficiency and a smaller land footprint.
The huge scale of UHV development reflects China’s geography as much as its climate ambitions. Energy resources are concentrated in the north and west, while electricity demand is highest in the east and south. UHV has therefore become the backbone of China’s long-standing “ west-to-east power transmission ” strategy.
But China’s UHV system was not originally designed for wind and solar. Early projects were built mainly to transmit hydropower, with a small share of coal. Both of these sources offer stable, high-output electricity well suited for transferring large amounts of electricity over long distances.
A major shift came in 2014, when severe air pollution in northern cities prompted the government to plan 12 “ air pollution control transmission corridors ”. The strategy sought to reduce coal-fired power generation in eastern regions by relying on electricity imports from the west.
Nine of these corridors were built as UHV projects and eight of those were designed to transmit coal-fired electricity. According to our Global Coal Plant Tracker , between 2016 and 2019, they were commissioned alongside nearly 50 GW of new supportive coal capacity, more than a quarter of China’s coal additions during that period.
The UHVs did help shift pollution away from cities in the east, but they also locked coal into long-distance power flows. Even today, wind and solar account for only around one-fifth of electricity transmitted through UHV lines – a share that has barely increased since 2021, despite the rapid growth of renewables nationwide. Under China’s 14th Five Year Plan, for 2021-2025, new UHV corridors were required to carry at least 50% renewable electricity. That represented significant progress from the current average of 21%, yet it means new corridors still could remain heavily backed by coal. Planned electricity output is often split evenly between fossil and renewable sources, making it difficult for renewables to dominate the transmitted power.
Policy and market need to accommodate renewables
Long-distance UHV power transmission typically involves sending regions, receiving regions and transmission operators that often belong to more than one power grid. Adding more wind and solar power necessitates increasingly complex coordination, including flexibility on both ends of the grid, “demand-side response” and greater use of power markets to trade electricity across regions and balance supply and demand in real time. What is demand-side response? Encouraging consumers to help balance the power system, through flexible pricing and monetary incentives, to shift their use of electricity to times when it is more plentiful or general demand is lower. This can make the grid more efficient, lower costs and also support greater use of renewable power.
The higher the share of renewables, the more difficult and costly system dispatch, grid management and cross-regional coordination become.
By contrast, transmitting coal power remains a familiar and simple solution, easing grid operators’ accountability burden of operational safety, supply security and price affordability.
The Qing-Yu UHVDC line highlights these complexities. Commissioned in 2020, it was the world’s first UHV corridor designed to transmit 100% renewable electricity, from Qinghai to Henan. Yet it has never delivered more than half of its designed annual transmission volume of 41.2 terawatt-hours.
Pricing in Henan – which is based on subsidised local coal power, including “capacity payments” plus a fixed transmission tariff – systematically disadvantages renewable power delivered through the line. What are capacity payments? These are subsidies given to energy generators in China, such as coal-power plants, gas power plants and storage facilities, for standing idle, ready to produce power if needed to meet peak demand.
Meanwhile, local flexibility resources are dominated by coal units, which struggle to absorb variable renewable output, limiting Qing-Yu’s potential to deliver more.
Technology is not the real constraint
From a technical perspective, this reliance on coal is not inevitable. High shares of renewables can create stability challenges for UHV systems, especially at the sending end, where local grids are weak. But coal is only one way to stabilise volatility and support the grid.
Alternatives such as pumped-storage hydropower, battery storage and concentrated solar power (CSP) with thermal storage can provide flexibility with minimal emissions. CSP plants usually use molten salt to store heat from concentrated sunlight, can ramp output faster than coal and provide stable generation after sunset.
The Lu-Gu UHVDC line linking eastern Inner Mongolia to Shandong shows what is possible by strengthening the AC grid at the sending end. Commissioned in 2017, the line does not rely on dedicated coal plants. Instead, it draws support from the wider north-east grid, allowing the flexible dispatch of thermal, hydro and renewable sources. In 2024, wind and solar supplied nearly 59% of the electricity transmitted, making Lu-Gu the only UHVDC corridor in China that achieves both high transmission volumes and a high share of wind and solar. State Grid Tibet’s Yangbajing high-altitude UHV test base (Image: Cynthia Lee / Alamy) Beyond strengthening local grids, voltage-source converter (VSC) HVDC technology offers another approach. VSC-HVDC can operate without strong AC grid support and respond to power fluctuations in milliseconds. Unlike conventional UHVDC systems, which rely on robust local grid support, VSC-HVDC enables large-scale transmission and high levels of wind and solar integration.
China has already demonstrated this potential. The Zhangbei ±500 VSC project supplied the Beijing 2022 Winter Olympics with 100% renewable electricity. Yet some newer UHV projects with VSC technology – for example, the Gansu–Zhejiang UHV-DC project currently under construction – continue to add large amounts of coal capacity, reflecting planning choices rather than technical necessity.
Unlocking renewable potential in China’s UHV grid
By 2030, China’s wind and solar megabases are expected to reach around 455 GW , equivalent to the total utility-scale wind and solar installation capacity across the Americas as of February 2026. Of this capacity, 315 GW is planned to be transmitted to the east through UHV transmission. Under current planning assumptions, delivering that electricity would require 104 GW of additional coal capacity at the sending end, 8% of China’s current operating coal capacity, effectively making renewables a driver of new coal construction.
On the receiving end, provinces importing large volumes of electricity continue to approve new coal plants to strengthen the regional grid and balance variability associated with imported electricity. An analysis published in November 2025 by Xue Xiaokang, a Green Finance campaigner at Greenpeace East Asia, describes this dynamic as “dual coal lock-in”: coal expansion at both the sending and receiving ends of UHV transmission, driven by risk-averse planning rather than system-wide optimisation.
China plans to add 15 new UHVDC lines, bringing total operating transmission capacity to over 420 GW by 2030. As wind and solar capacity soars, UHV transmission needs to become greener, allowing fewer UHV lines to carry more renewable energy. The technology exists. What’s needed now is a decisive shift in priorities across technology, policy and market. Done right, UHV can help phase out coal rather than lock it in, and play a pivotal role in China’s energy transition and climate goals.
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