Solar Power Cuts Coal Use; But Issue Does Not End Here

August 13, 2026

India’s rapid solar expansion has reduced fossil fuelbased electricity generation in the middle of the day by 10 gigawatts (GW), equivalent to the output of around 15 modern coal power units, according to a new analysis. But fossil generation after sunset has risen by 22 GW, the analysis by global energy think tank Ember found, highlighting India’s growing need for battery storage and other sources of flexibility in the power system. On an average day in the first half of 2026, fossil generation fell to around 125 GW at 1 pm, compared with 135 GW at the same time in the first half of 2023. But between 5 pm and 7 am, fossil generation averaged 168 GW, up 22 GW from three years earlier, according to Ember. The analysis showed that coal plants are ramping down during solar-rich hours before increasing output sharply to meet evening demand. The average gap between fossil generation at the 1pm low of 125 GW and the 7pm peak of 174 GW was nearly 50 GW in the first half of 2026, equivalent to more than 70 modern coal power units. On the sunniest days, coal generation is already reaching a technical minimum, leading to wind and solar curtailment to keep coal plants online during the day, Ember said. The growing pressure on India’s grid has also been reflected in disturbances recorded in renewable energy complexes. The disturbances were mainly in renewable energy complexes in Rajasthan and Gujarat and were linked to non-compliance by some generators with low-voltage ride-through and high-voltage ride-through requirements. Battery storage can help address the mismatch by capturing surplus solar generation during the day and releasing it in the evening, when electricity demand remains high and coal generation is at its greatest. India has shown how quickly solar can reduce coal generation during daylight hours. The next step is extending those benefits beyond sunset. Battery storage allows cheap daytime solar to meet evening demand, reducing pressure on coal-fired generation while making better use of renewable electricity that would otherwise go unused. Battery storage can also help limit renewable energy curtailment, improve the use of existing solar capacity and provide greater flexibility to the electricity system. The economics of battery storage have changed significantly in recent years. Ember said the emergence of lithium iron phosphate batteries had helped transform storage economics, with global average installed costs falling 95 per cent from $2,634 per kilowatt hour in 2010 to $140 per kilowatt hour in 2025. Performance, safety and cycle life have also improved. The India findings form part of Ember’s broader analysis of how battery storage is changing the role of solar power globally. Solar generated just over 10 per cent of global electricity in the first half of 2026, up from 8.9 per cent in the same period of 2025 and 5.6 per cent in the first half of 2023. Solar generation increased from 769 terawatt hours in the first half of 2023 to 1,564 terawatt hours in the first half of 2026. Total power generation increased by 12 per cent over the same period. On an average day in the first half of 2026, solar met more than 25 per cent of global electricity demand between 11 am and 2 pm. But its contribution fell to near zero between 8 pm and 5 am. In markets where solar supplied more than 20 per cent of electricity, it met more than half of midday demand before again falling to near zero after sunset. This creates a growing challenge for power systems with high solar penetration. As solar generation rises during daylight hours, fossil generation remains more entrenched after sunset. Some mature markets are also beginning to face negative prices, curtailment and slower solar deployment during periods of high midday generation. It is estimated that global battery additions could reach 459 gigawatt hours (GWh) in 2026, up 50 per cent from 307 GWh in 2025. If all the batteries were used to shift solar generation, they could theoretically move 34 per cent of new daily solar generation into non-sunny hours, compared with 18 per cent in 2025 and 4 per cent in 2021. It may be cautioned that this is a theoretical ceiling because batteries are not always used for solar shifting and many remain underutilised. Around a quarter of new utility-scale solar capacity deployed globally in 2025 was co-located with batteries, according to the report. Battery deployment had moved from a niche technology to a mainstream solution in less than five years. The ability of batteries to shift solar varies substantially between markets. Bulgaria and Chile added enough battery capacity in 2025 to shift 77 per cent and 76 per cent, respectively, of their new daily solar generation into non-sunny hours, followed by Australia at 60 per cent. Battery deployment is changing evening electricity supply in several markets. In California, solar combined with batteries met more than a quarter of electricity demand during the evening peak between 7 pm and 9 pm on an average day in the first half of 2026, compared with 6.8 per cent in the same period of 2023. In Chile, batteries helped solar meet more than 10 per cent of electricity demand during the evening and into midnight in the first half of 2026. In Bulgaria, solar combined with batteries met nearly a quarter, or 24 per cent, of electricity demand during the evening peak between 7 pm and 9 pm, and averaged 10 per cent of demand between 7 pm and 7 am. Battery storage is not sufficient to address longer periods of low solar generation. A balanced clean power system would also require complementary resources, including wind, hydropower, nuclear power and long-duration energy storage. Long-duration storage technologies, including newer battery technologies, thermal storage, gravity-based storage and compressed air storage, could potentially store electricity for several weeks, although most remain at early stages of research and demonstration. Simply installing batteries would not be enough. Market rules need to allow storage systems to access multiple revenue streams and participate in energy, ancillary service and capacity markets. The report cited China as an example of the utilisation challenge. Standalone batteries in China cycled an average of 299 times in 2025, up from 146 cycles in 2022, but still below international best practice of around 350 cycles a year. Co-located batteries cycled even less, averaging 199 times in 2025. The analysis concludes that the next phase of solar growth will depend increasingly on how effectively power systems can integrate and use flexibility, rather than simply on adding more solar capacity. For India, Ember said this means the benefits already visible from solar during the daytime will increasingly depend on the country’s ability to shift renewable electricity into the evening, when demand is high and coal generation remains dominan