Slovenia’s transmission system operator ELES has proposed ending some network-fee exemptions for large batteries and pumped-storage hydropower from 2027, earlier than developers had expected. The proposal puts tariff treatment and project economics in focus for storage investors.
Under current rules, eligible batteries connected to medium- and high-voltage networks receive an exemption from transmission and distribution charges and connection-capacity fees for three years after obtaining operating permits. The exemptions cover both network charges and connection-capacity fees.
Pumped-storage hydropower plants receive longer exemptions, lasting at least 12 years. ELES’s proposal would end some of these exemptions, although the facts available do not specify which categories would be affected.
ELES argues that storage installations require grid investment and that network operators should not have to finance the associated infrastructure without receiving corresponding tariffs. The operator has previously identified an annual network-funding gap of more than €100 million.
Storage developers say changing the rules would alter project economics after investment assumptions had already been made. Batteries use the network when charging and again when discharging, making tariff design an important operating-cost factor.
Storage economics are also moving beyond calculations based only on day-ahead arbitrage and balancing revenues. Network fees, connection charges and regulatory treatment can materially change project returns, according to the issues raised in the debate.
The dispute is an early warning for the wider southeastern European storage market. As battery deployment accelerates, governments and system operators will have to determine how storage contributes to network costs without undermining investment in the flexibility needed for renewable integration.
