Day-ahead exchange trading in 15-minute instead of 60-minute intervals

Previously, electricity was traded in 60-minute time intervals in the so-called day-ahead auction. These are now being shortened to 15 minutes. The regulatory basis for this are two regulations that stipulate a 15-minute imbalance settlement period (ISP): the EU Electricity Regulation (EU) 2019/943 and the EU Regulation establishing a guideline on system balancing in the electricity supply system (Electricity Balancing (EU) 2017/2195).1

This has been obvious at the latest since the increasing integration of renewable energies: as their production can fluctuate significantly within an hour, faster reactions to fluctuations in supply and demand make sense, and not just in intraday trading. Short intervals also enable day-ahead electricity procurement to be more in line with demand and significantly increase market efficiency and flexibility - so the shorter time interval ultimately leads to better integration of renewables into the market.

Postponement to October

The changeover was initially planned for 11 June 2025, but after extensive tests, EPEX Spot rejected the go-live in June and pleaded for October. The reason was significant operational concerns following tests. According to the company, central matching algorithms were heavily burdened by the increased complexity. Around 20 per cent of the tests led to complete market decoupling - meaning that connected markets were disconnected and cross-border electricity flows could no longer take place.2 In addition, delays in the publication of results jeopardised market stability. All in all, an unprecedented risk.

Technical details

The complexity is indeed very high. All bidding zones are to be converted to the new system at the same time in order to avoid market distortions. As a result of the changeover, the market clearing price will be changed to a 15-minute resolution and will have two decimal places. In future, exchanges such as EPEX Spot will publish a 60-minute price index, but this will only be an arithmetic mean of the corresponding 15-minute prices for an hour. Where there is currently only one clearly defined day-ahead price, there will be two published prices in future.

Effects on market participants

In addition to the stock exchanges, all market participants must also adapt to the new 15-minute interval. For them, too, this will lead to significantly greater complexity in the processing of all trading activities: they will have a much higher data and computing effort and will have to adapt IT systems and processes. In addition, contracts will have to be adapted - for example those between system operators and direct marketers. Provision must also be made for a possible fallback to the old system.

However, this effort is also offset by opportunities, as ultimately everyone benefits from more precise pricing and better integration of flexibility - the market, renewables and all market players.

Do you have any questions about the changes to day-ahead trading on EPEX SPOT? Please get in touch with us!

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¹ https://eur-lex.europa.eu/legal-content/DE/TXT/PDF/?uri=CELEX:32019R0943, https://eur-lex.europa.eu/legal-content/DE/TXT/PDF/?uri=CELEX:32017R2195

² https://www.epexspot.com/en/news/market-coupling-steering-committee-aligns-revised-go-live-date-15-minute-mtu-sdac