On 30 September 2025, for delivery on 1 October, the Single Day-Ahead Coupling (SDAC) introduced a 15-minute market time unit across its participating bidding zones, with Ireland remaining at 30-minute resolution. EPEX SPOT published its first coupled quarter-hourly results at 13:08 for the 96 intervals of 1 October. On EPEX SPOT's side, the launch covered 11 countries; Great Britain and Switzerland were outside the coupled rollout.
On a normal 24-hour day, participating day-ahead markets now produce 96 quarter-hourly clearing prices instead of 24 hourly prices. EPEX SPOT still allows 60-minute and 30-minute contracts through cross-product matching, but the coupled market's minimum time unit and clearing-price resolution are 15 minutes.
By July 2026 - roughly nine months after go-live - this is no longer a reform in waiting. It is the normal design of most of the coupled European day-ahead market. The change has not removed intraday trading, nor has it made weather the only driver of electricity prices. It has, however, made intrahour production profiles more visible at the day-ahead stage.
Why the market switched
The reform was introduced as part of the EU market framework for finer time resolution in power trading and imbalance settlement. Its purpose is to improve market efficiency and make it easier to represent electricity supply and demand that change within an hour. That is particularly relevant for renewable generation: solar output ramps through sunrise and sunset, while wind can change with fronts, turbulence and local weather.
Under the previous hourly day-ahead design, the base clearing interval could not fully express those intrahour shapes. Market participants could refine their positions closer to delivery through intraday auctions and continuous trading, which already offered 15-minute products. Quarter-hourly day-ahead clearing moves part of that shaping into the noon auction on the preceding day, while intraday markets remain available for later forecast updates and portfolio adjustments.
What the early data showed
The first months did not produce an instant clean break with hourly behaviour. FfE, the German research institute, analysed day-ahead and intraday prices after the launch and found that the familiar 'sawtooth' pattern - systematic quarter-hour price deviations associated with hourly scheduling - remained visible at first and also appeared in the day-ahead market. FfE discussed several possible explanations, including procurement in hourly block products and market participants needing time to adapt bidding processes and plant schedules.
By December 2025, the pattern had weakened substantially in the European countries examined. FfE interpreted the decline as evidence that at least part of the initial effect was transitional, consistent with participants adjusting bidding strategies and dispatch planning. This was an early-post-launch analysis, not a complete nine-month study, so it supports a direction of travel rather than a final verdict on the reform. [3]
FfE also found that the day-ahead market recorded the highest intrahour volatility on a large share of days in its study period. That does not mean all market risk moved into day-ahead trading. It indicates that more of the quarter-hourly shape that had previously emerged in intraday auctions was already visible in the day-ahead clearing prices.
Volumes moved in the same direction. In FfE's dataset, day-ahead traded volume reached 26.7 TWh in October 2025, the highest monthly level of that year, and remained high in November and December. At the same time, volume in the first intraday auction fell to levels not seen since 2020. These figures are consistent with some trading activity shifting earlier, although they do not prove a one-for-one transfer between markets.
Weather forecasting at the market's new resolution
The practical consequence for renewable operators is not that every weather change automatically sets the price. Quarter-hour prices still emerge from aggregate bids, demand, available generation, cross-zonal capacity and network constraints. A forecast error also does not automatically become an imbalance, because participants can continue adjusting positions in the intraday market.
What has changed is the resolution at which the day-ahead schedule is valued. A cloud band that changes solar output for 30 minutes, or a wind ramp that arrives earlier than expected, can affect the expected generation profile of specific quarter-hours rather than being averaged into a single hourly position. This increases the value of forecasts that resolve fast changes and communicate uncertainty at the same scale as the market.
The day-ahead order book closes at 12:00 CET on the day before delivery. Operators therefore need a credible interval-by-interval production profile at that point, followed by updated forecasts as delivery approaches. Intraday trading remains essential for responding to new observations and reducing residual exposure.
For solar assets, sunrise and sunset ramps, passing cloud and convective development are natural areas of focus. For wind assets, fronts, gusts, icing conditions and changes in boundary-layer structure can alter production over short periods. The operational question is no longer only 'How much energy will this site generate tomorrow?' It is also 'What is the expected profile, how uncertain is it, and when should that expectation be updated?'
Planning with the OpenWeather Energy Dashboard
OpenWeather's Energy Dashboard is designed as a monitoring, forecasting and risk-assessment environment for solar and wind installations. For solar sites, it uses irradiance components - global horizontal irradiance (GHI), direct normal irradiance (DNI) and diffuse horizontal irradiance (DHI) - together with installation parameters such as panel area, peak power, tilt and azimuth. For wind sites, it provides multi-altitude wind profiles and relates them to hub height, rated power and turbine power curves.
The Energy Dashboard presents generation forecasts in both hourly and 15-minute intervals, giving operators a detailed view of short-term production changes. Solar forecasts are available in 15-minute steps for the next 12 hours, while wind forecasts extend across the next 24 hours at the same resolution. Hourly generation forecasts cover the next 24 hours, supported by a wider 48-hour weather outlook.
This mix supports short-term production planning and comparison with quarter-hourly market or grid schedules. Operators can use the outputs alongside their existing trading, grid and asset-control processes to inform scheduling, maintenance and curtailment planning. [
The Dashboard also supports expected-versus-actual performance analysis, where operational generation data are available, helping teams identify possible underperformance. Site-level risk scoring combines current weather, forecasts, official alerts and installation-specific parameters into a 0-100 Red-Amber-Green assessment. Risk scores are recalculated every hour or when new official weather alerts are issued, while the portfolio map displays site status and alert polygons.
For operators managing distributed portfolios, the value lies in bringing several operational views together: installation-specific production estimates, short-term interval traces, actual-versus-expected performance, weather alerts and prioritised site risk. That information can help teams decide where to investigate underperformance, reschedule maintenance or prepare for weather-related operating limits.
The new rhythm is established
Nine months after launch, 15-minute day-ahead pricing is the normal market design across most SDAC bidding zones. Early evidence shows that the transition did not eliminate intraday trading or erase legacy price patterns overnight. It did bring more intrahour detail into day-ahead price formation, and market behaviour began adapting within the first months.
For renewable operators, the enduring lesson is straightforward: daily energy totals are no longer enough for day-ahead planning. Decisions increasingly depend on the shape and uncertainty of generation within the day, together with a process for updating that view as delivery approaches. Weather has always changed in minutes. Europe's coupled day-ahead market now values much of that change in 15-minute intervals.
Explore the OpenWeather Energy Dashboard to see how site-specific production forecasting and weather-risk monitoring can support your solar and wind portfolio.