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Glossary · Energy industry & energy transition

BELIX, Belgian Electricity Index

BELIX Belgian Electricity Index Belgium electricity market EPEX SPOT Belgium Belpex Day-ahead market power exchange price index market price Exchange electricity price bidding zone

BELIX stands for Belgian Electricity Index. The index condenses the prices of the Belgian day-ahead market of EPEX SPOT into a single daily value. According to the current index description of EPEX SPOT (as of July 2026), BELIX is identical to the index "BE epex DA MCP base". This is the arithmetic mean of all market clearing prices of a delivery day from 0:00 to 24:00 CET/CEST in the Belgian bidding zone. It is expressed in euros per megawatt hour (€/MWh). BELIX is therefore neither a general electricity price nor a retail price. It is a reference value determined on the exchange for electricity deliveries on the following day in a clearly delimited market area.

The reference unit megawatt hour measures a quantity of energy, not instantaneous power. A BELIX of 100 €/MWh corresponds to 10 cents per kilowatt hour, calculated without grid fees, levies and taxes. Since the day-ahead market has traded in quarter-hours, a worked example helps: anyone drawing 1 megawatt for a quarter of an hour consumes 0.25 MWh. At a quarter-hour price of 100 €/MWh, this quantity costs 25 euros on the exchange. The distinction between energy and power is important. Price indices value quantities of energy, whereas grid operation and security of supply depend mainly on power, load profile and short-term balancing capability.

Calculation and time grid

The coupled European day-ahead auction takes place at 12:00 CET for the following delivery day. Buy and sell orders from all participating exchanges (NEMOs) are matched by the EUPHEMIA algorithm together with the cross-border transmission capacities. This yields a market clearing price for each delivery period. Since delivery day 1 October 2025, these delivery periods have been quarter-hours instead of hours in all SDAC bidding zones. On a normal day, 96 quarter-hour prices therefore feed into BELIX. On the days of the clock change, there are 92 and 100 respectively. Before the changeover, BELIX was the mean of 24 hourly prices. Important: the index is a simple, non-volume-weighted average. Each quarter-hour counts equally, regardless of the traded volume.

Besides the base index, EPEX SPOT publishes further day-ahead indices for Belgium. The peak index is the average of the delivery periods from 8:00 to 20:00, the off-peak index the average of the remaining periods. There are also the individual quarter-hour prices and the hourly index ID60, i.e. the mean of the four quarter-hour prices of an hour. It is intended for contracts that continue to settle hourly. In the current index list, the name Belix applies only to the base index. By contrast, an older index description of EPEX SPOT from 2020 also listed BELIX Peak, BELIX Off-Peak and monthly values. These designations may therefore still appear in older contracts.

BELIX Base is a different quantity from a single quarter-hour or hourly price. A daily average can look calm even though there were very low or even negative prices at midday with plenty of solar power and pronounced price spikes in the evening at high demand. For procurement, market analysis and contract valuation, precisely this difference can be decisive.

A bidding zone is neither an individual grid connection point nor a balance group. It is a market area in which a uniform price applies in day-ahead trading. According to the Belgian regulator CREG, EPEX SPOT Belgium trades energy for injection and withdrawal in the Belgian bidding zone. Physical congestion within the country is handled through grid operation and redispatch and is not directly visible in BELIX.

Origin: Belpex and EPEX SPOT Belgium

BELIX goes back to the Belgian power exchange Belpex. According to CREG, the market rules of Belpex were approved by ministerial decree of 11 January 2006. From the outset, the exchange was price-coupled with the Dutch APX and the French Powernext in order to increase liquidity on the spot market. According to a Belgian comparison portal, the Belpex day-ahead market started on 21 November 2006. Belpex was merged into EPEX SPOT in 2015 and has officially been called EPEX SPOT Belgium since the end of 2016. Alongside the day-ahead auction, EPEX SPOT Belgium also operates continuous intraday trading.

There are differing statements on the ownership of the trademark. The index description of July 2026 calls Belix a registered trademark of European Energy Exchange AG, whereas the 2020 version calls it a trademark of EPEX SPOT SE. Both companies belong to the EEX Group. In terms of concepts: Belpex was the exchange or its name, BELIX is an index. An exchange organises auctions and trading, an index condenses prices according to fixed rules. In Belgium, "Belpex price" is often used in everyday language for the individual quarter-hour or hourly prices. The service provider Elexys, by contrast, publishes under the name BELIX a monthly average to which variable supply contracts refer. Anyone reading a contract should therefore check which definition, which time reference and which data source is meant.

Distinction from retail price, intraday and forward market

BELIX is a wholesale value. On an electricity bill, grid fees, taxes, levies, sales and metering costs, risk premiums and the supplier's margin are added. These components of the electricity price are not contained in the index. A variable contract may refer to BELIX, to a monthly value or to quarter-hour prices. Which energy price actually has to be paid only follows from the price formula in the contract.

The day-ahead price is fixed on the previous day. Intraday prices arise closer to the time of delivery and react more strongly to short-term changes, such as power plant outages, new wind forecasts or changed load assumptions. Prices on the forward market apply to later months, quarters or years. They reflect expectations about fuel and CO₂ prices, demand and power plant availability as well as risk premiums. BELIX therefore does not show a long-term electricity price level, even though long BELIX time series are well suited for analyses.

What determines the index value and what it is used for

Belgium is closely connected to its neighbouring markets via interconnectors. Market coupling feeds the available cross-border capacities directly into price formation. The Belgian day-ahead price therefore depends not only on Belgian generation and Belgian consumption. It is also influenced by French nuclear availability, gas-fired power plants in the region, wind and solar generation, fuel and CO₂ prices, and grid capacity at the borders. How strongly the values fluctuate is shown by the monthly averages from Elexys: around 448 €/MWh in August 2022 at the peak of the energy crisis, around 48 €/MWh in April 2024 and around 174 €/MWh in October 2026.

Generators read from the index whether feeding in on the following day is worthwhile or whether flexibility is worth more. Consumers with dynamic or indexed contracts can see when electricity is expensive or cheap. Traders, suppliers and industrial companies use the index for procurement, portfolio valuation and settlement. For storage and load shifting, what matters is less the daily average than the price spread within the day. A battery storage system earns from the difference between charging and discharging times, minus losses, costs and risks. For precisely this spread, EPEX SPOT offers its own index for Belgium (BE epex DA TBx). It measures the difference between the average of the x most expensive and the average of the x cheapest delivery periods of a day.

Typical misinterpretations

  • High BELIX equals supply emergency: High prices can point to scarcity but do not directly measure security of supply. This depends on firm capacity, reserves, balancing energy, import possibilities and grid stability. A high price can also simply result from expensive marginal power plants. Conversely, a moderate daily average can mask tight individual quarter-hours.

  • Negative prices mean worthless electricity: Negative prices arise when, in the submitted bids, supply exceeds the demand willing to pay. Possible reasons are minimum loads of power plants, support rules, generation coupled to heat or industrial processes, and too little flexible demand.

  • BELIX says something about the origin of the electricity: The index values a standardised delivery in a bidding zone. Whether a consumer is currently drawing electricity from gas, nuclear, wind, solar or imports cannot be read from it. There are separate instruments for that, such as guarantees of origin.

Informative value and limits

BELIX is useful because it creates a precise reference point. Instead of speaking generally of the Belgian electricity price, one can state exactly what is meant: the base index, a quarter-hour price, a peak value, a monthly average or a contractually derived retail price. However, the index does not replace an analysis of total electricity costs. It contains no grid fees, no costs for congestion management or hedging, no taxes and no investment costs. It initially shows only what result the day-ahead auction delivered under its rules for the Belgian bidding zone. Anyone who uses the term properly distinguishes bidding zone, delivery period, calculation rule, time grid (hour or quarter-hour) and contract level.

Sources

Related glossary entries

Edited by eCMS on 11.11.2026 15:26

© 2026 Erik Schmidt. All rights reserved. Quotations with a link to the source are welcome.