On the extended May Day weekend in 2026, a familiar but increasingly systemically relevant phenomenon reappeared in the German electricity market: a so-called Hellbrunn. This describes a situation where high feed-in from photovoltaics and wind occurs simultaneously with comparatively low electricity demand – resulting in sometimes extreme price reactions on the electricity exchange.
Record high negative electricity prices
On May 1st, between 1:15 PM and 2:30 PM, spot market electricity prices reached -499.99 €/MWh nearly the technically defined price floor. Such a strong price level was last observed in July 2023. Later in the day, the market turned significantly: in the evening, prices rose to up to 232.99 €/MWh (23.3 ct/kWh).
This resulted in an exceptional Day-ahead spread of €732.98/MWh. This was not only a record high negative electricity prices, but also a clear signal of structural imbalances in the electricity system.
On May 2nd, the trend continued: prices fell again to up to -120 €/MWh. The main cause was the combination of:
- High solar and wind power generation
- low demand due to holiday and weekend
- limited flexibility options in the power system
Power grid under pressure: Oversupply at lunchtime
At its peak, PV generation on May 1st was around 46 GW, while total electricity generation was approximately 59 GW reached. In contrast, there was a comparably low load of about 43 GW.
The resulting oversupply was partially offset by:
- 5–6 GW pumped storage capacity, that consumed electricity
- run 10 GW electricity exports abroad
However, neighboring countries were also affected by high PV feed-in, which limited export capacities and demand.
Redispatch: Interventions are becoming the rule
In such situations, transmission system operators increasingly resort to Redispatch measures back. Power generation plants are specifically ramped down or up to avoid grid congestion.
The consequences:
- Curtailment of renewable energies, especially photovoltaics
- rising System costs, as operators are compensated for lost feed-in
- additional burden on grids and market mechanisms
The costs of Redispatch have been continuously rising for years and regularly reach billions. Heat waves significantly exacerbate this problem, as large amounts of energy must be taken out of the system at short notice.
Why negative electricity prices are increasing
Negative electricity prices are no longer isolated incidents, but rather an expression of a structural trend. The main drivers:
- Dynamic expansion of PV systems without simultaneous expansion of flexibility
- Inflexible production structures (e.g., conventional power plants with minimum load)
- Weak demand On weekends and holidays
- Limited storage and load shifting capabilities
With the ever-increasing share of solar power, this pattern will intensify in the future, especially during midday hours.
Battery storage as a key to the solution
The targeted expansion of Battery storage systems is considered the central answer to the challenges of the Hellbrise. It can take on several system-relevant functions:
1. Recording of surplus electricity
Battery storage systems charge specifically at negative prices, thus preventing curtailments.
Stabilization of electricity prices
Arbitrage smooths out extreme price spikes and reduces volatility.
3. Relief of the Redispatch System
Fewer interventions by grid operators mean lower system costs.
4. Provision of Balancing Power
Large-scale storage can also supply primary and secondary control energy, thereby opening up additional revenue streams.
5. Integration of Renewable Energies
Storage increases the system's capacity for additional PV power.
Conclusion: Flexibility determines system efficiency
The light breeze on the first May weekend in 2026 clearly shows: The expansion of renewable energies alone is not enough. Without the parallel development of flexibility options – especially through battery storage – system costs, redispatch requirements, and market distortions will increase.
For companies, energy providers, and investors, this results in clear areas of action:
- Integration of Storage in Energy Projects
- Using price signals through intelligent marketing
- Combination of PV systems with flexibility solutions
The energy transition is thus entering a new phase: Not just generation anymore, but system integration is becoming the decisive success factor.