No group in Greece may own or control more than 500 MW of battery storage. If the country reaches 7 GW of battery energy storage systems (BESS) by 2030, the top of its Energy Ministry's range, that takes at least 14 optimizers a bank will accept. At the Solarplaza Seminar BESS Greece in Athens on 24 September 2026, that single rule surfaced in three of the four sessions. This article zooms in on one theme from our full post-show report.
Key takeaways
- The cap now covers trading. Since the end of July 2026, the 500 MW limit counts projects under management and aggregator agreements, not only ownership.
- Lenders feel it first. Banks want optimizers with a track record, and the experienced ones will hit the cap.
- Skill varies widely. The optimizer's fee is 3% to 7% of revenue on a merchant deal. The gap between a good and a poor one is far larger.
- Owners need their own yardstick. Greece has no public league table, so benchmarking has to be written into the contract.
A rule built for a market that does not exist yet
The cap began as a limit on subsidized auction projects. Virginia Murray, Partner at Watson Farley & Williams, explained that it was widened at the end of July to include managed and aggregated capacity, with annual declarations. Asked whether aggregators could find a way around it, she did not hedge: "It's really quite strict the way it's currently phrased. So no."
Apostolos Panos, President of the Hellenic Association of Energy Storage Systems, accepts the reasoning. The ministry wants to avoid the concentration Greece already has in gas-fired flexibility. His problem is the sequence. With only 600 MW to 700 MW of batteries operating, he argued, "we must create the market" before regulating competition inside it.
He also ran the numbers from the other direction. Few companies in Greece can offer the tolling agreements and hedges that lenders ask for. Multiply those few by 500 MW each and you get about 2.5 GW through 2029.
Why your bank cares who trades
Murray's slides spelled out what lenders will check: historical returns, strict benchmarks, and a commitment to respect the battery's warranty limits. The cap means "the banks will not necessarily be able to rely on optimizers that they have seen before". Finding 14 good ones, she said, is "going to be quite a challenge for the Greek market".
Christos Pantazis of Metlen Energy & Metals described the same squeeze from a utility's side. Metlen backs the ministry's aim, he said, but new counterparties with smaller balance sheets will have to step in and support tolling deals.
What separates a good optimizer from a busy one
The early Greek data already shows a spread. Nicolas Kyriakoglou, Manager at Baringa, compared the 11 batteries trading so far. Their day-ahead results look alike. Their balancing results diverge sharply, and two assets on the same day can follow opposite strategies.
Liuba Andreeva, Head of Go-to-Market at Capalo AI, listed what sits behind good performance:
- Reliable price forecasts for every market, including balancing, which few providers sell
- Remote control logic tested on the physical asset
- Real-time visibility for the owner, technical and financial
Her test for a partner is whether they can explain themselves. "You need to understand in all the details what actually this company is doing," she said.
How owners keep score
Joshua Murphy, Head of Energy Storage at Econergy, pays optimizers 3% to 7% of revenue on merchant deals. He will pay the top of that range for results: "If they're going to earn me 20% more revenues, I'll give them 7%. Absolutely fine."
He checks constantly. In the United Kingdom, a public league table ranks every battery, and Murphy admits to phoning his optimizer after a single bad day. Greece has no such table. His methods for markets without one:
- Give similar assets to two optimizers and use each as the other's benchmark.
- Pull every optimizer's data into your own system in one format.
- Put daily, monthly, cycling, and competitor reporting in the contract before signing.
- Add a benchmarking clause. Two review periods in the bottom half of the market, and the optimizer can be replaced.
Short terms help too. Murray noted that 12-month optimization agreements are usual internationally, so owners can switch when returns fall short.
Will the cap last?
Large players hope not. Konstantinos Natsis of PPC Renewables, which plans 2.4 GW of flexible capacity across the region by 2030, said he hopes the measure comes "out of the table" so more can be built in Greece.
Andreeva took the other side, and she trades for a living. In Poland, she said, the grid operator steps in once an aggregator grows large enough to move prices. She thinks that is how it should be: "It's impossible to become a huge aggregator without being noticed."
For now the rule stands, and it opens the door to new entrants. Murray's summary works as advice for both sides of the table: the cap 'will give space for a lot of new optimizers to come into the market, but banks will have to then become comfortable with those new optimizers'.
Read the full report
The 500 MW cap is one of eight themes in our post-show report on the Solarplaza Seminar BESS Greece. It also covers the 2030 forecasts, grid connection delays, duration choices, financing terms, and the revenue stack.
The storage conversation continues at the Solarplaza Summit Bulgaria on 14 October 2026 in Sofia, the Solarplaza Seminar BESS Czechia on 19 November 2026 in Prague, and the Solarplaza Seminar BESS Ireland on 26 November 2026 in Dublin.
