icon-twitter

On 1 October 2025, the European Day-Ahead (DA) trading was converted to 15‑minute trading products. This reform was implemented simultaneously by all Nominated Electricity Market Operators (NEMOs) across all participating Member States. The objective of the reform is to improve the integration of renewable energy sources and to enhance overall market efficiency.

Until now, the so-called “sawtooth pattern” had been observable in the Intraday (ID) markets—particularly in the auctions—due to the different product granularities compared with the DA market. This pattern resulted from the mismatch between hourly DA products and quarter-hourly ID products: within each hour, systematic alternations between overestimations and underestimations of load occurred, leading to price jumps between consecutive quarter-hours. A detailed explanation can be found in Chapter 3 of our publication at the IEWT.

Prior to the transition, it was widely expected that introducing quarter-hourly products in the DA market would lead to a smoothing of ID prices. However, the data show that the characteristic sawtooth pattern persists after the transition and is now also visible in the DA market. The following explanations have been discussed for the continued existence of the sawtooth pattern and its apparent transfer to DA prices:

One possible reason discussed is that procurement on upstream forward markets still relies on block products, making additional intrahour balancing procurement necessary.
The argument that cross-border trading continues to be conducted on an hourly basis is incorrect; the transition to quarter-hour products in cross-border trading had already taken place earlier [1].
A frequently cited explanation is that many market participants have not yet been able to adapt their internal processes: they continue to submit mainly hourly bids and base their dispatch planning on hourly generation schedules.

In the following analysis, we examine the deviation of DA and ID prices from a linear, interpolated DA price trajectory, as well as the intrahour standard deviation of prices. The findings show that price deviations in the DA market have declined significantly since the transition and that the sawtooth pattern in the DA market has been noticeably attenuated. At the same time, it becomes evident that part of the previously required short-term balancing is increasingly absorbed in DA trading.

The extent of the sawtooth pattern has decreased since the transition

Figure 1 compares the development of DA and ID prices in early October and early December. The sawtooth pattern appears very similar across the markets shown, but its intensity is clearly less pronounced in December than it was in October.

AFigure 1: Comparison of DA and ID Auction prices on selected days in October and December

This observation is also confirmed by Figure 2, which shows the absolute deviation of IDA1 and DA prices from a quarter-hour interpolation of hourly DA prices (and, after the transition, from an interpolated linear DA trajectory) for the years 2023 to 2025. Since October 1, 2025, these deviations have declined significantly, suggesting that at least part of the previously pronounced sawtooth pattern was attributable to market participants’ adjustment processes, such as changes in bidding strategies and power plant dispatch planning. The deviations of DA and IDA1 prices in 2025 follow a similar pattern and, with the exception of the first half of October immediately after the transition, are clearly below the deviations observed in 2023 and 2024.

Figure 2: Deviation from a linear trajectory of DA-prices, one-week moving average of daily means, compar-ison over the years 2023 to 2025

Trading activity shifts from the first Intraday Auction to the Day-Ahead market

Figure 3 illustrates that deviations from a linear trajectory—and thus the intensity of the sawtooth pattern—have declined significantly across all markets since October. Deviations in DA prices are smaller than those in ID auctions, which is partly due to additional influencing factors in ID auctions such as forecast errors and short-term market changes. These factors increase with the time gap between auction closure and the DA market, which explains why IDA3 shows the largest deviations—though not necessarily due to a stronger sawtooth pattern, as Figure 1 demonstrates when comparing DA and IDA1 prices.

Figure 3: Deviation from a linear trajectory of DA prices, one-week moving average of daily means, comparison across DA and the first (IDA1), second (IDA2), and third (IDA3) ID auctions

To enable a comparison of intrahourly price fluctuations between markets, Figure 4 shows the intra-hourly standard deviation. Here, too, a clear decline in intrahourly volatility toward the end of the year is visible in both DA trading and ID auctions. Since the introduction of quarter-hour products, the DA market exhibits the highest intrahourly volatility on most days, indicating that part of the remaining intrahourly balancing is increasingly absorbed in the DA market—either to offset forward market posi-tions or because some participants have not yet adapted their bidding strategies sufficiently.

Figure 4: Intrahourly standard deviation, one-week moving average of daily means, comparison across DA and the first (IDA1), second (IDA2), and third (IDA3) ID auctions

Parallel to this, a clear shift in traded volumes can be observed: DA market volume reached 26.7 TWh in October 2025, the highest level of the year, and remained only slightly lower in November and Decem-ber at 24.4 TWh and 26.1 TWh, respectively. In contrast, the traded volume in IDA1 dropped to 0.56 TWh in October and further declined to 0.42 TWh in both November and December—the lowest values observed since 2020 (when only one ID auction existed). Volumes in subsequent auction stages IDA2 and IDA3 remained at levels comparable to the period before the transition. The development of ID auction trading volumes in 2024 and 2025 is shown in Figure 5.

Figure 5: Monthly trading volume of the ID auction markets in 2024 and 2025

The sawtooth pattern is visible across Europe

Figure 5 shows the deviation of DA-prices from an interpolated, linear trajectory (top) as well as intrahourly standard deviation (bottom). A pronounced deviation from a linear price path can be observed in all countries. While the magnitude differs across countries, it has been declining in all markets since the introduction of 15‑minute products in October. This indicates that in all European markets, the sawtooth pattern is visible, yet declining.

Figure 6: Price deviations in the DA market following the introduction of 15 minute products

Weiterführende Informationen

Literatur

[1] EEX – EPEX Spot (2025): 15-Minute products in market coupling, https://www.epexspot.com/en/15-minute-products-market-coupling (zuletzt aufgerufen am 12.01.2026)