The electricity grid: a matter of balance

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In short

• The grid stays in balance through three consecutive steps: nominating, adjusting intraday and balancing at the last moment.
• Transmission system operator Elia monitors the grid frequency of 50 hertz and activates various types of reserves to do so.
• Imbalance is a cost when expectations and reality diverge, but it also creates opportunities for flexibility.
• The better the forecast, the smaller the gap between expectation and reality.
• Batteries and other flexible assets play a role mainly when fast or targeted corrections are needed.

Why is the balance between production and consumption so important?

On a large scale, electricity cannot simply be stored. Production and consumption need to match almost exactly at every moment to keep the electricity grid stable. You do not see that balance directly, but it shows up in the grid frequency.

“In the European electricity system, that sits around 50 hertz,” Matthias explains. “When production and consumption diverge, that frequency changes. For grid operator Elia, that is an important signal to intervene. It sounds complex, but the conclusion is actually simple: energy is not just about how much electricity is produced or consumed, it is also about the timing of when the two come together.”

How does that balance come about?

The first step happens through planning. Market parties indicate in advance how much electricity they expect to produce or take off. Based on that, supply and demand are matched as closely as possible in the day-ahead phase.

“That planning is obviously not a crystal ball,” Matthias says. “It is a well-founded estimate based on, among other things, consumption, production, weather data and portfolio knowledge. That is why forecasting plays such an important role. The better the forecast, the smaller the gap between what was expected and what happened. And the less correction work is needed afterwards.”

What if the plan does not match reality?

“That is where intraday comes in,” Matthias replies. “That phase gives suppliers and Balance Responsible Parties (BRPs) the chance to adjust their position during the day once it becomes clear their portfolio is deviating from their original nomination. Think of it as the last chance to correct before the system itself steps in. On the European electricity market, alongside the day-ahead auction, there are also intraday markets, including continuous trading right up until close to delivery. In practice, that absorbs many day-to-day deviations. Solar output comes in lower than forecast, a production process needs more energy than expected, or an asset behaves differently than planned: through intraday, parties can still adjust their position and already smooth out part of the gap.”

And what if there is still a gap?

Then we are talking about imbalance. The remaining mismatch at the moment itself, so to speak. Everything not resolved by planning and intraday corrections still needs to be absorbed in real time to keep the grid stable.

“That is also where the economic incentive comes in,” Matthias notes. “Imbalance has a price. Whoever is structurally off feels that. Something to avoid, in other words. At the same time, the need for balancing creates opportunities for parties that can respond flexibly. So, it is a misconception that imbalance is only a cost.”