Day-Ahead Trading in 15-Minute Intervals: The New EU Standard from October 2025

On October 1, 2025, a new era will begin in European power trading: the central Day-Ahead auction will switch from hourly to 15-minute products. With this step, the transmission system operators are implementing an EU mandate designed to make the power market more precise across Europe.

The major advantage for marketing is that the volatile fluctuations in electricity volumes, primarily caused by renewable energies, can now be traded with much greater temporal accuracy.

Objectives of the EU-wide reform

The basis for this reform lies in EU Regulations 2019/943 and 2017/2195, which obliged all transmission system operators to harmonize the Imbalance Settlement Period (ISP) across Europe to 15 minutes. This automatically requires the NEMOs (Nominated Electricity Market Operators) to provide corresponding products in all SDAC-coupled markets.

The internal electricity market also stipulates that trading intervals must be no longer than the ISP. This makes the 15-minute interval in the Day-Ahead market a regulatory necessity.

The impact of the reform differs across European countries. In Germany, the shift mainly affects the central 12:00 auction, since Intraday products and other market segments are already based on 15-minute intervals. France, by contrast, faced a much larger adjustment: balancing energy had to move from 30 minutes to 15 minutes earlier this year.

These differences highlight the overarching goal of the reform: to achieve harmonization and a uniform market structure across Europe.

Expected effects of the switch to 15-minute Day-Ahead trading

The reform is expected to lead to more precise price formation. By introducing quarter-hourly products, the deviations between Day-Ahead forecasts and actual renewable generation will be significantly reduced.

The reason is that typical feed-in patterns – such as the steep PV ramps in the morning and afternoon or short-term wind fluctuations – can be captured far more accurately with 15-minute intervals than with hourly products. The same applies to consumption peaks: load curves can now be mapped in greater detail.

As a result, forecasts will align more closely with actual generation and demand, reducing deviations in balancing group management and lowering the need for balancing energy or corrective Intraday trading. Quantitatively, this effect can be measured by comparing forecast errors on an hourly basis (1H-FC) with those on a quarter-hourly basis (QH-FC).

It is also expected that the matching of supply and demand will improve already within the auction itself. Until now, many corrections had to be made in the Intraday market.

These will increasingly be captured directly in the Day-Ahead auction, delivering efficiency gains for both traders and system operators.

Market implications and price developments

The introduction of 15-minute products on EPEX SPOT will also affect price dynamics. Our trading experts expect volatility in Day-Ahead trading to resemble that of the 15:00 Intraday auction, which traditionally shows much stronger price swings than hourly products. Short-term ramps and fluctuations will be reflected more directly in prices – offering both opportunities and risks for traders and portfolio managers.

Despite the closer integration with Day-Ahead, the Intraday market will remain highly relevant. Ongoing forecast updates for renewables will continue to drive prices and liquidity. However, some corrections that previously occurred exclusively in Intraday will now shift to the Day-Ahead auction, likely leading to an earlier concentration of liquidity.

The future of trading strategies and battery storage marketing

The move to 15-minute products will significantly increase the requirements for risk management and trading strategies. The higher complexity makes extensive automation indispensable – from forecasting and trading decisions to execution. Only with automation can the much larger data volumes be processed efficiently and reliably.

For storage marketing, however, this does not create systematic advantages over other technologies. While more granular products open up additional arbitrage opportunities, the role of the currently central 15:00 Intraday auction may diminish, as part of the price signals will already be absorbed in Day-Ahead. Storage operators will therefore need to focus on continuous optimization and multi-market strategies rather than relying on individual auctions.

Technical challenges

Alongside the benefits, the reform also poses significant technical and operational challenges. Instead of 24 products per day, market participants will now need to forecast, trade, and settle 96 products. This quadruples the data volume and compels traders and portfolio managers to adopt higher levels of automation. Without corresponding upgrades, the risk of technical errors and delays increases.

It will also be interesting to observe how conventional power plants adapt to the new 15-minute products. Until now, scheduling has usually been based on full hours. In the future, operators could optimize their plants more flexibly, ramping up at 16:30 or 16:45 instead of waiting until 17:00. This would allow short-term price signals to flow directly into dispatch decisions. For the market, this could mean additional liquidity and tighter coupling of supply and demand – but also increased volatility in generation schedules.

Finally, the resilience of the system during the transition remains a question. In EPEX tests, the auction failed to run stably in around 20% of cases, which led to the postponement of the original go-live date from June 11, 2025, to October 1, 2025. This highlights ongoing operational risks. Robust fallback procedures, stress tests, and clear communication processes will be critical to ensure a smooth start.

Handling existing contracts: Transparency is key

For a long time, it was unclear how existing hourly contracts would be handled in the new 15-minute market. It is now confirmed: the hourly price will continue to exist, calculated as the average of the four quarter-hourly prices. This preserves the established practice in direct marketing and PPAs.

Nevertheless, transparent methods for determining and invoicing these prices will be crucial. Clear rules and communication are essential to ensure trust between contractual partners and to avoid disputes.

suena energy: Transparent storage marketing

The switch to 15-minute products is both regulatorily irreversible and a true milestone for the market. It promises more precise prices, lower balancing costs, and better integration of renewable energies. At the same time, it makes trading more complex – technically, operationally, and contractually.

At suena, we focus on maximum transparency in Day-Ahead trading. Through our trading dashboard, operators have real-time access to all trading and storage activities, as well as to billing-relevant data. Our reporting makes schedules, orders, and pricing mechanisms fully transparent – strengthening trust and fairness in an increasingly complex 15-minute market.

At the core of our marketing services lies our AI-based suena Energy Trading Autopilot. Our platform processes large data volumes in real time and optimizes the operation and trading of battery storage. Weather forecasts, current market data, and technical parameters such as aging and efficiency losses are continuously integrated, ensuring that trading decisions are well-founded and storage systems respond instantly to fluctuations in the grid.

With technologies like our suena Energy Trading Autopilot, October 1, 2025, will mark a milestone – not a stress test – for market participants.