Bulgaria is riding a fast boom in battery storage that has come along with its solar power surge, AFP reports in a new analysis. It comes just as an unprecedented drought makes it harder for several eastern European countries to produce power.
About a hundred storage sites are now running across the country — on old airfields, in factories and next to power plants. The energy ministry says battery systems already working had a combined capacity of around 5.7 gigawatts as of September. Under the EU recovery plan, contracts have also been signed for projects with a storage capacity of 14 gigawatt-hours.
"The scale and speed of battery storage rollout in Bulgaria is unprecedented by European standards," says Stavros Papathanasiou, a professor at the National Technical University of Athens.
The new capacity makes Bulgaria's power grid more flexible right when extremely low water levels on the Danube are hurting power output in several countries in the region. In July and August, Bulgaria's net power exports averaged about 830 gigawatt-hours a month — more than double the average for May and June. In July, most of that power flowed to Romania, and net transfers across that border were worth around 74 million euros at Bulgarian market prices, AFP reports.
The shift shows up most clearly at the Maritsa East 3 plant, once the country's second-biggest coal power station. The plant was built with four 210-megawatt units. It sharply cut coal power output after its long-term contract ran out in 2024. Part of its old grid connection is now used for a battery installation instead.
"We could make use of that key grid connection. We decided to shut down one coal unit and hook the batteries up there," Vasil Shtonov, head of ContourGlobal in Bulgaria, tells AFP.
He says that flexibility matters a lot, because about two-fifths of the country's power comes from the Kozloduy nuclear plant, and Bulgaria has far fewer gas plants — which can ramp output up or down easily — than Greece or Romania.
"Coal is on its way out, batteries are coming in. This was the right place at the right time," Shtonov says.
Still, he thinks Bulgaria should keep a small reserve of coal capacity in place, just in case of a harsh winter or a break in gas supplies.
Nikola Gazdov chairs the Bulgarian Association for Electricity Production, Storage and Trade. He says the fast rise of batteries owes more to a lucky mix of circumstances than to any planned strategy.
"It all happened by chance," he tells AFP.
Renewables in Bulgaria are growing mainly thanks to solar plants, which produce bigger and bigger surpluses of power during the day. Battery systems, by contrast, are relatively easy to build — Gazdov reckons a large project can be ready in under 18 months.
In 2025, Bulgaria accounted for around 9% of all new battery storage capacity installed in Europe. The country could "serve as a good example for other European countries," says Lennart Herrmann, a senior consultant at the Munich-based energy research center FfE.
Still, there are limits to how far Bulgaria can become a "battery of the Balkans." Grid links with neighbouring countries have limited capacity, and current battery systems typically hold power for one to six hours, sometimes up to eight, Herrmann explains. That's enough to cover demand peaks or short dips in output from hydro and nuclear plants, but batteries can't replace a nuclear reactor that's offline for days or weeks.
If battery capacity grows too fast, it could squeeze the profits batteries themselves make. Batteries charge up when power is cheap and sell it back when prices are high, earning money on the gap between the two. The more such systems run at the same time, the smaller that gap gets.
Even with those limits, batteries can smooth the energy transition by cutting the need to curb renewable output or fall back on fossil fuels, Herrmann says.