Bulgaria has become one of the world’s leading markets for battery energy storage, with capacity added in 2025 theoretically enough to shift 77% of the country’s new daily solar power generation to the hours without sunlight, according to BTA and Agerpres.
This puts Bulgaria at the top of the markets analyzed, narrowly ahead of Chile (76%) and Australia (60%), according to a new analysis published by Ember, an energy think tank.
Battery storage capacity has grown at a particularly rapid pace in Bulgaria. The country added about 3 gigawatt-hours (GWh) of new storage capacity in 2025, after having virtually no such capacity just a year earlier. By May 2026, installed capacity had doubled to 8.6 GWh. According to Ember, this growth has been supported by government funding and simplified permitting procedures, with continued expansion expected until 2030.
The data shows that the development of battery technology is already changing the role of solar energy in Bulgaria’s electricity system. In the first half of 2023, solar energy made no contribution to meeting evening electricity demand. Three years later, the combination of solar and batteries covered, on average, almost a quarter, or 24%, of the country’s electricity demand between 19:00 and 21:00.
Between 19:00 and 07:00, solar energy stored and later delivered via batteries accounted for, on average, about 10% of electricity consumption. According to Ember, Bulgaria has seen the most significant transformation among the major markets analyzed, with a substantial portion of the strong growth in solar power now reaching consumers outside of daylight hours.
In California, by comparison, solar and batteries covered more than a quarter of electricity demand between 7:00 p.m. and 9:00 p.m. in the first half of the year, up from 6.8% in the same period in 2023. In Chile, batteries already allow solar to cover more than 10% of demand during the evening and into midnight.
In this context, the EU as a whole lags behind the leading markets. Last year, 27 GWh of battery storage capacity was added to the bloc, theoretically enough to shift only 16% of new daily solar power production to other time slots. This figure was below the global average of 18%. However, scenarios developed by European transmission system operators estimate that between 2025 and 2030, the installed capacity of battery storage in the EU will be four times higher.
Ember stressed that the 77% figure for Bulgaria represents the theoretical potential of new batteries in relation to the increase in solar power generation and not the actual measured share of electricity transferred over time. Not all batteries are used exclusively for storing solar energy, and how they are used also depends on the rules of the electricity market.
For the calculations for Bulgaria, the analysts used hourly data provided by the European Network of Transmission System Operators for Electricity (ENTSO-E). The data on solar power generation includes the charging and discharging processes of batteries located on the premises of solar power plants. Since off-grid battery activity is not reported as a separate category, Ember estimates it based on the difference between reported hourly consumption and the sum of production and net imports, while also accounting for the impact of pumped storage hydroelectric plants.
The report places Bulgaria’s development in the context of the rapid expansion of solar power worldwide. Solar power plants generated just over 10% of global electricity production in the first half of 2026, a new record and almost double the 5.6% share recorded in the first half of 2023. Solar power production increased from 769 terawatt-hours (TWh) to 1,564 TWh during this three-year period, while total global electricity production increased by 12%.
According to the analysis, the main challenge is the strong concentration of solar power production during daylight hours. On a typical day in the first half of 2026, solar power plants covered more than 25% of global electricity demand between 11:00 and 14:00, but their contribution fell to almost zero between 20:00 and 05:00. As a result, fossil fuels continue to play a significant role after sunset, even in markets with a high share of solar energy.
The rapid decline in battery costs is starting to change this. The average global cost of installing battery storage systems has fallen by 95%, from $2,634 per kilowatt-hour in 2010 to $140 in 2025. New battery storage capacity worldwide is expected to reach 459 GWh in 2026, 50% more than the 307 GWh added in 2025. In theory, this new capacity could shift 34% of new daily solar power generation to off-peak hours, compared with 18% in 2025 and just 4% in 2021.