EPEX Spot. It sounds like the kind of acronym that belongs in a risk management presentation rather than a conversation about your electricity bill. But the European Power Exchange is actually one of the most important and transparent price signals in the entire European energy system — and understanding how it works is the foundation of understanding dynamic energy.

What EPEX Is

EPEX Spot is a pan-European electricity exchange, headquartered in Paris, that facilitates the trading of short-term electricity contracts across much of continental Europe, the UK, and Scandinavia. It operates two main markets that are relevant to retail dynamic pricing: the day-ahead market and the intraday market.

Belgium, along with the Netherlands, Germany, Luxembourg, France, and several other countries, participates in a price coupling mechanism — meaning that prices in interconnected markets are determined simultaneously by a shared algorithm that optimises cross-border flows across the available interconnector capacity.

The Day-Ahead Market

By 12:00 noon each day, generators and large buyers across participating countries submit their bids and offers for each hour of the following calendar day. The exchange algorithm clears these orders to find the price at which supply and demand balance for each hourly slot. Results are published by approximately 12:30 CET.

This gives you 24 hourly prices — your roadmap for the next day's electricity costs. Most smart energy management systems consume this data automatically and use it to schedule flexible loads. As a 10s Energy customer, you see exactly the prices your consumption will be billed at, the moment they are published.

The Intraday Market

After day-ahead prices are set, the intraday market allows continuous trading up to close to the delivery hour. This is where large players fine-tune their positions — adjusting for wind forecast changes, unexpected demand shifts, or generation outages.

For most retail dynamic tariff customers, the day-ahead price is the relevant reference. Intraday prices are important for understanding why prices sometimes deviate from what was expected, and they become more relevant as energy management systems become more sophisticated.

What Drives Prices Up and Down

The core logic of electricity price formation is supply and demand, but with some important specificities. Supply is dominated by the merit order: generators are dispatched in order of their marginal cost, from cheapest (renewables with near-zero variable cost) to most expensive (gas peakers). The price is set by the most expensive generator needed to meet demand.

This means prices are lowest when renewables are abundant and demand is low — overnight, weekends, high-wind days, sunny midday periods. They are highest when demand is high and expensive gas or oil generation is setting the price — cold winter evenings, low-wind periods, and periods of high industrial activity.

Understanding this pattern is not just academically interesting. It is the basis for every load-shifting decision that saves you money on a dynamic tariff.