China, already the global leader in renewable energy generation capacity, is racing ahead in building new wind and solar farms, but progress is slower on its showcase wind and solar 'mega' bases, a think tank said on Thursday.

China had installed 365 gigawatts (GW) of wind power capacity and 392 GW of solar capacity by the end of last year, about a third of the world's total.

It looks set to reach a total of 1,200 GW of wind and solar energy by 2025, five years ahead of a government target, U.S.-based think thank Global Energy Monitor (GEM) said in a report, thanks to generous subsidies and a low-cost supply chain.

GEM's outlook is in line with the International Energy Agency's view.

However, GEM said progress is slower on Beijing's most ambitious projects, dubbed 'mega' bases, or gigawatt-scale wind and solar energy parks located in remote regions, which are technically more challenging and face stricter requirements.

China's state planner, the National Reform and Development Commission (NDRC), announced plans in 2021 to build 97 GW of large-scale solar and wind projects in sparsely-populated northwestern regions such as Inner Mongolia and Xinjiang to be completed between 2022 and 2023.

In 2022, the NDRC announced a second target to build a further 200 GW of capacity at even larger bases by 2025.

While the first round of smaller projects are likely to be completed on time, the second batch will be more challenging to finish on schedule, GEM said.

Among four main desert energy bases with a combined planned capacity of 119 GW by 2025, only 1 GW of solar components appear to be under construction, with the remainder of the projects still in the feasibility study or permitting stages, GEM said.

"The application requirements for the second batch have become noticeably more stringent," said GEM project manager Dorothy Mei.

Alongside delays in planning and approval and construction of transmission lines, the new bases are also required to manage peak loads and integrate with the grid, said Mei, which requires use of energy storage technologies.

However, the government is likely to intervene to expedite the process, she added.

(Reporting by Andrew Hayley; Editing by Sonali Paul)