According to the information compiled by the energy think tank Ember from its latest report on solar energy and battery storage systems, the increasing battery capacity in parallel with the rapid growth in solar energy plays an increasingly important role in transferring the electricity produced during the day to sunless hours.
According to the report, 459 gigawatt-hours of new battery capacity is expected to be commissioned worldwide this year. This amount represents a 50 percent increase compared to the 307 gigawatt-hour capacity added in 2025.
According to Ember's calculation, new batteries installed this year could shift 34 percent of daily solar production to evening hours. This rate was at 18 percent in 2025 and 4 percent in 2021.
The report states that the 34 percent rate is a theoretical upper limit, that in practice not all batteries are used to carry solar electricity to sunless hours and that some systems are not used enough. Better market design and optimization is required to fully exploit the potential of batteries.
The distribution of solar energy production during the day is also effective in the importance of batteries. While the share of solar energy in global electricity production exceeded 10 percent in the first half of the year and reached a record level, global solar production increased from 769 terawatt hours in the first half of 2023 to 1564 terawatt hours in the same period of 2026.
According to Ember's calculation, on an average day in the first half of 2026, solar energy will meet more than 25 percent of global electricity demand during the hours of 11.00-14.00, while the share of direct solar generation approaches zero during the hours of 20.00-05.00. This situation increases the importance of batteries, which allow the production during daylight hours to be stored and used during sunless hours when demand continues.
BATTERY COSTS DECREASED 95 PERCENT IN 15 YEARS
Among the developments that support the acceleration in battery investments, the decrease in storage costs stands out.
According to the report, especially with the developments in lithium iron phosphate technology, the global average installation cost of battery storage systems was 2 thousand 634 dollars per kilowatt-hour in 2010, and decreased to 140 dollars in 2025.
Thus, while costs decreased by 95 percent in 15 years, improvements were also made in the performance, safety and cycle life of the batteries. Ember states that with these developments, battery storage has become an economical and scalable tool that can transport the electricity produced from the sun during the day to sunless hours at a low cost.
Installing solar and battery systems together is also becoming common. Approximately a quarter of the new large-scale solar capacity deployed worldwide in 2025 will be installed with battery systems.
THE SHARE OF SOLAR AND BATTERIES IN EVENING DEMAND IS INCREASING
In some markets where battery capacity is rapidly increasing, the share of solar energy and batteries in evening electricity demand is also increasing.
Bulgaria and Chile have stood out globally by installing enough new battery capacity to shift more than three-quarters of their daily new solar generation to hours when the sun is not shining by 2025. This rate was 77 percent in Bulgaria and 76 percent in Chile, while Australia followed them with 60 percent.
In the US state of California, where solar energy is produced intensively, solar and batteries met more than a quarter of the electricity demand between 19.00 and 21.00 on an average day in the first half of the year.
While the contribution of solar energy in the evening hours in Chile and Bulgaria in the first half of 2023 was almost non-existent, on an average day in the first half of this year, batteries met more than 10 percent of the electricity demand between 19.00-21.00 in Chile and 24 percent in Bulgaria.
The report emphasizes that the increase in battery investments alone is not sufficient, and that market design that will enable storage systems to access different income sources such as energy arbitrage, ancillary services and capacity payments is also important. According to Ember, the next growth phase in solar energy will be determined by how quickly batteries will be deployed and how effectively they will be integrated into electrical systems.
