Why Electricity Is Now Bought and Sold in 15-Minute Blocks?
Since October 1, a new rule has changed how electricity is traded across Europe: instead of hourly trading, the market now operates in 15-minute intervals (instead of hourly).
Blog
30/10/2025
Behind this shift, known as the “15-Minute MTU Switch,” lies a major transformation: a more precise, responsive market that’s better suited to the rise of renewable energy. In concrete terms, electricity prices now adjust more frequently, following the rhythm of the wind, the sun, and demand a change that fits perfectly with ENGIE’s ambition, by integrating more clean energy efficiently and using smarter tools to manage it.
To understand what’s behind this change, we spoke with Alexandre Huynen, Team Leader Short Term Power for the Central Western Europe region. A specialist in short-term power markets, Alexandre leads a team covering the week-ahead, day-ahead, intraday, and imbalance horizons. Their mission: to analyze market dynamics, heavily influenced by weather, anticipate price movements, and provide risk signals to the trading and algo-trading teams.
Alexandre, why is this shift so important?
Until now, electricity was mostly traded in one-hour blocks, for example, buying or producing a certain amount between 10 a.m. and 11 a.m. But the energy world is changing fast…
With the rapid growth of solar and wind, production can fluctuate much more quickly, sometimes within just a few minutes, depending on cloud cover or wind speed.
At the same time, new technologies likebatteries and flexible consumption (industrial sites, data centers, electric vehicles, etc.) allow demand to be adjusted almost in real time.
As a result,hourly trading no longer reflects the reality of the system. We needed a market that could keep pace with the wind, the sun, and new consumption patterns.
So, what’s changing, exactly?
The idea is to move from anhourly market to one based on 15-minute intervals. In practice, this means electricity market participants, producers, suppliers, traders, aggregators, and others no longer submit offers like ‘from 10 a.m. to 11 a.m.’ but instead four 15-minute offers: 10:00–10:15, 10:15–10:30, 10:30–10:45, and 10:45–11:00.
This changeimproves the match between what’s forecasted, produced, and consumed, which means fewer last-minute corrections. The new market design was rolled out across Europe on September 30, 2025, with the first 15-minute electricity deliveries starting on October 1, 2025.
What motivated this shift?
It’s part of the EU’s Clean Energy Package, aiming to:
Better integrate renewables like solar and wind.
Harmonize wholesale markets and balancing mechanisms.
Enable more precise use of cross-border transmission lines (interconnectors).
Can you give us a concrete example?
The switch to 15-minute trading brings the market closer to the physical reality of the power system and improves its economic efficiency. Take this example:
At 2 p.m., the sun is shining and solar panels produce a lot
At 2:30 p.m., clouds roll in and production drops sharply
Previously, the market treated the full hour (2 p.m.–3 p.m.) as a single block, with a stable price throughout. Now, prices can vary from one 15-minute period to the next, lower when production is high, higher when it falls. As a result, price signals are more accurate. Batteries, flexible demand, and responsive producers can react more effectively and capture more value.
What does this mean for market participants?
Better integration of renewables: The market can finally follow the real pace of wind and solar generation.
More value for flexibility: Fast-reacting resources (batteries, demand response, flexible generation) are better rewarded.
More dynamic pricing: Prices can shift more frequently, creating new opportunities and more volatility.
Increased complexity: Moving from 24 to 96 Market Time Units (MTUs) per day requires stronger forecasting models and IT systems
New working methods: Trading, balancing, and optimization teams now have to think in 15-minute blocks instead of hourly ones.
The 15-minute market opens real opportunities for ENGIE to boost operational efficiency and flexibility. It improves alignment between weather forecasts, market signals, and trading decisions from week-ahead to real-time. This new framework helps balance portfolios, manage risks, and better anticipate price movements in a fast-changing environment.
Any early pricing effects?
We’re seeing a “zigzag” or “saw tooth” effect in electricity prices within the same hour, especially in the morning and evening when the sun rises or sets.
This reflects:
Rapid changes in solar output or demand
Uneven flexibility and liquidity, with part of the market still bidding hourly conventional power plants while renewable and batteries increasingly operate at 15-minute resolution.
The stronger the variation within an hour, the more 15-minute prices diverge from the hourly average.
“In summary, this is a major step forward for Europe’s power market. The shift to 15-minute trading marks a key milestone in modernizing the European electricity market. It’s a powerful lever to integrate more renewables, unlock flexibility, and reduce gaps between forecasts and reality.“
Claudia Wilmart, BESS Program Leader
What are the 3 Key Takeaways of this shift?
More precise, dynamic prices: The market now adjusts every 15 minutes. Fluctuations in production and demand are reflected more quickly, allowing batteries, flexible producers, and consumers to respond faster.
Better integration of renewables: Solar and wind generation can finally be valued more accurately, and the grid can adapt more effectively to rapid changes in supply and demand.
A new way of working: ENGIE International Supply & Energy Management teams now think in 15-minute blocks instead of hourly ones, adjusting forecasts and tools to make the most of the new, finer-grained market design.
What is an MTU?
MTU stands for Market Time Unit, the time block used for trading electricity.
👉 Switching from 60-minute to 15-minute MTUs makes the market more responsive to fast-changing conditions. 👉 The day is now split into 96 blocks instead of 24, with prices set every 15 minutes. 👉 Producers and consumers can better match real-world conditions, especially for renewable and flexible assets.
👉 By storing excess renewable electricity and releasing it when production drops, these systems help smooth the fluctuations of solar and wind generation, exactly the kind of short-term variations the new MTU design captures. 👉 Ultra-responsive, batteries can react within milliseconds, making them perfectly suited to this more granular market. They not only stabilize the grid but also create new value streams, charging when prices are low and discharging when they rise. 👉 For ENGIE, optimizing BESS is already a strategic focus. Advanced algorithms now allow ENGIE’s teams to maximize the performance of these assets across time frames – from intraday arbitrage to system balancing – helping accelerate the shift to a low-carbon, more resilient energy mix.
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