Global Solar Crosses 3 Terawatts — And Hits a Wall

By the end of 2025, the IEA Photovoltaic Power Systems Programme estimated global cumulative capacity at approximately 2,974 GW, with about 698 GW installed that year alone . Solar now supplies approximately 9% of global electricity generation .

China's dominant but infrastructure-constrained role

China remains the engine of global solar expansion, building more wind and solar capacity than the rest of the world combined . Its utility-scale solar pipeline alone reached 664 GW . However, the grid is not keeping pace. Severe transmission bottlenecks — especially between remote renewable megabases in the north and west and population centers in the east — have led to soaring curtailment rates, with large volumes of clean power simply wasted .

Solar curtailment in resource-rich provinces like Qinghai, Xinjiang, and Gansu has risen to between 10% and 17% due to grid congestion and limited electricity market flexibility . Nationally, curtailment rates surged to 9.2% for solar and 8.5% for wind in early 2026 .

The bottleneck has become a brake on new builds. Solar installations in China plunged 56% year-on-year in March 2026 and 79% in April . China's solar market is now heading for its first annual contraction since 2019 . Grid operators invested ¥167.5 billion ($24.5 billion) in Q1 2026 alone to try to catch up, but rigid market rules and coal-linked transmission arrangements remain obstacles . The inflexible management of coal plants and power grids — not a lack of generation capacity — is the primary cause of this wasted output . Carbon Brief found that China's CO₂ emissions actually climbed 2% in early 2026 partly because wasted wind and solar forced continued coal burning . Wind and solar account for only about 20% of the electricity flowing through ultra-high-voltage lines, whereas coal power supplies 42% .

The rooftop solar boom in developing countries

While China's utility-scale growth stalls, a rooftop solar surge is transforming markets across the global south:

Pakistan saw an "unprecedented" surge in solar adoption, with solar electricity production reaching more than three times the global average . Rooftop solar output was expected to exceed grid demand during daytime hours in several key industrial hubs . Pakistan briefly became China's No. 2 solar export market before being overtaken by the Philippines . By early 2026, Pakistan had avoided more than USD 12 billion in oil and gas imports that would otherwise have been needed to meet domestic energy demand .

The Philippines has been the world's fastest-growing solar market in 2026, driven by soaring electricity prices and frequent outages . Rooftop solar capacity nearly doubled from 721 MW in early 2025 to around 1,300 MW by early 2026 . Payback periods fell to just three years for residential systems, 2.3 years for commercial, and 3.1 years for industrial . China exported more than 3,000 MW of solar panels to the Philippines in March and April 2026 alone . In the first three months through May 2026, panel imports reached $407 million, a 145% increase .

Nigeria has also seen an extraordinary increase in rooftop installations, alongside smaller markets like Cuba and Lebanon . Africa recorded its fastest year of solar growth in 2025, with installations rising 54% year-on-year, led by South Africa (1.6 GW) and Nigeria (803 MW) . The number of countries with at least 1 GW of solar installed has grown to as many as 74, up from 42 in 2020 .

The critical need for battery storage

The solar surge has created a growing "midday glut" problem. In China, the sheer volume of solar generation has severely outpaced grid integration capabilities, leading to elevated curtailment and wasted output . More than 150 regions in China have been classified as "red zones" where the local power grid can no longer accommodate additional photovoltaic power generation .

Battery storage is the key to shifting midday solar oversupply into evening peak hours, preventing negative or zero electricity prices, displacing fossil peaker plants, and improving the economics of existing solar farms. A PNAS study on China's decarbonization route concluded that terawatt-level energy storage deployment is needed to absorb surplus generation . SolarPower Europe's Global Solar Market Outlook 2026-2030 notes that the sector is shifting from rapid deployment to integration challenges, as high penetration rates drive curtailment, storage demand, grid constraints, and evolving policy and market designs . Without rapid storage deployment, the value of new solar capacity diminishes sharply, and the grid-level waste problem will intensify as additional terawatts come online.

Outlook

The global solar market appears on course for its first market contraction in over 20 years. SolarPower Europe forecasts a temporary decline in global installations in 2026, with its medium scenario anticipating an 8% year-on-year drop to 612 GW, before growth resumes in 2027 . This anticipated contraction is attributed largely to solar market restructuring in China .

The next phase of the solar transition is no longer about manufacturing and installing panels; it is a system-integration test centered on transmission infrastructure and energy storage. As Global Energy Monitor noted, China's wind and solar deployment has "moved from an installation race to a system-integration test" . The question is no longer whether the world can build solar capacity at scale, but whether it can use that capacity effectively.