Battery storage opens evening electricity markets to solar: Ember

Battery storage is pushing solar power beyond daylight hours and into electricity markets long dominated by fossil fuels, according to a report from energy think tank Ember.

The analysis, published August 12, finds solar and batteries already supplied roughly a quarter of evening electricity demand in California and Bulgaria during the first half of 2026.

Globally, batteries expected to be installed this year could shift 34 per cent of new daily solar generation into evening hours, based on solar growth during the first six months. That compares with 18 per cent in 2025 and just 4 per cent in 2021.

Ember cautions that the estimate is a theoretical ceiling. It assumes all the new batteries are used to shift solar electricity. Actual performance depends on how storage is operated and whether electricity market rules allow batteries to earn revenue from multiple services.

The findings point to a new phase of solar expansion.

Solar supplied just over 10 per cent of global electricity in the first half of 2026, nearly double its 5.6 per cent share three years earlier. On an average day, it met more than a quarter of demand between 11 a.m. and 2 p.m., before falling to almost nothing overnight.

That concentration creates problems in markets already producing abundant midday solar electricity. Wholesale prices can turn negative, generators may be forced to curtail output, and returns on additional solar projects weaken.

Batteries can store that electricity for later use, reducing waste and allowing solar to compete during evening demand peaks.

In California, solar and batteries met more than a quarter of demand between 7 p.m. and 9 p.m. in the first half of 2026, up from 6.8 per cent in the same period of 2023.

Bulgaria reached 24 per cent during those evening hours. In Chile, batteries helped solar meet more than 10 per cent of electricity demand through the evening and into midnight.

“Solar’s role in global power systems can be far bigger than previously thought possible,” Ember analyst Kostantsa Rangelova said in the report.

Deployment is accelerating. Ember cites projected global battery additions of 459 gigawatt-hours in 2026, a 50 per cent increase from 307 gigawatt-hours last year.

But installing equipment is only part of the challenge.

Batteries can earn money by shifting electricity between low-price and high-price hours, supporting grid stability and providing capacity when needed. Rules that let operators combine those revenue streams can improve utilisation.

China illustrates the gap. Standalone batteries averaged 299 charge-discharge cycles in 2025, while batteries installed alongside generation averaged just 199. Ember compares that with international best practice of about 350 cycles annually.

Storage also has limits. Today’s batteries primarily address daily fluctuations, leaving prolonged cloudy weather and seasonal shortages as continuing challenges.

Ember says electricity systems will still need a complementary mix of wind, hydro, nuclear and longer-duration storage.

The next stage of solar growth will depend increasingly on deploying batteries and integrating them into electricity markets, the report concludes. That makes market reform central to further expansion.