October 26, 2026
What are green energy certificates (GSC) and how do they work for businesses?
If you operate a commercial solar installation in Belgium, you’ve probably already heard of green energy certificates—or GSCs, for short. They’re an important source of revenue for many installations, but the system isn’t always transparent. How exactly do you earn them? What are they worth? And what changes are coming in the next few years?
Published by
Olivier Maurissen
Covolt Belgium
What is a green energy certificate?
A green energy certificate (GSC) is official proof that a certain amount of electricity was generated from renewable sources. In Belgium, one GSC is automatically issued for every MWh of green energy produced—provided your installation is certified and connected to the certificate system.
GSCs are issued by the Flemish VREG, the Walloon CWaPE, or the Brussels-based Brugel, depending on the region where your installation is located. They are tradable: energy suppliers are legally required to offer a certain percentage of green electricity and purchase GSCs from producers for this purpose.
The value of a GSC fluctuates, but for commercial solar installations it typically ranges between €60 and €100 per certificate—that is, per MWh of production.
How do you receive GSCs?
For larger installations (typically over 250 kWp), allocation is based on measurement data. For smaller installations, a fixed allocation formula based on theoretical output is sometimes used.
What will change starting in January 2027?
The rules for awarding GSCs will become stricter as of January 1, 2027. Specifically, GSCs will no longer be awarded for electricity generated during a 15-minute period when the electricity price is negative. This also applies to electricity that you consume locally.
Until now, that penalty only applied after 6 or more consecutive hours of negative prices. That threshold is being eliminated entirely. Just 15 minutes of negative prices is enough to forfeit the certificate for that 15-minute period.
In practice, this means that facilities that do not actively control their output when prices are negative are structurally missing out on GSC revenue. The more solar energy fed into the grid—and Elia expects Belgian solar capacity to grow to between 11 and 25 GW by 2035—the more frequently negative prices occur, and the greater the risk.
How can you minimize the loss?
First, the honest answer: you cannot keep the certificates for quarters with a negative price. They expire, regardless of whether you feed that electricity into the grid, store it, or consume it yourself. Based on 2025 prices, a 400 kWp system would thus lose nearly a quarter of its production in certificates: 91,620 out of 380,000 kWh per year. With a certificate value ranging from €93 to €450, that amounts to €8,520 to €41,227 per year.
What you do have control over, however, is what happens during those peak hours. If your system continues to generate power uncontrolled, you lose out twice: you won’t receive a certificate, and with a contract that follows the market price, you’ll also have to pay to feed your surplus into the grid. For the same 400 kWp system, that costs an additional nearly €3,000 per year on the day-ahead market. Added together, the loss amounts to between €11,441 and €44,148 per year, and the amounts scale linearly with capacity.
Turning everything off is the wrong reflex. Then you’ll be buying expensive electricity from the grid for power you could have generated yourself. And inverters that are turned on and off manually all the time wear out faster and can even break down.
The solution is dynamic curtailment: your system continues to generate the amount of electricity your company consumes, and simply curtails the surplus. Or you can store that surplus in a battery to use it yourself later. This happens automatically every quarter-hour, because it’s not possible to do it manually.
And this trend is becoming more significant, not less so. The number of hours with a negative electricity price in Belgium rose from 222 in 2023 to 404 in 2024 and to more than 520 in 2025. In 2026, the number will be slightly lower, but each hour with a negative price will cost a company more than before: less frequent, but more expensive.
Covolt handles this entirely automatically through the Covolt Horizon platform, based on day-ahead and intraday price signals. You don’t have to do anything yourself. Just make sure it’s set up before January 1, 2027—not after.
When is it worth setting this up properly?
GSC revenue is a key component of your system’s business case. The larger the system and the more energy you feed back into the grid, the greater the risk that the new regulations will affect you. A 300 kWp system that continues to operate without control could lose out on thousands of euros in certificates each year under the new rules.
Would you like to know how significant the impact will be for your specific installation? Covolt will calculate it for free based on your location, connected capacity, and historical production profile.
Covolt Belgium
Protect Your GSC Revenue for 2027
Covolt handles this entirely automatically through the Covolt Horizon platform, based on day-ahead and intraday price signals. You don’t have to do anything yourself. Just make sure it’s set up before January 1, 2027—not after.
Contact in Belgium
9 Filip Williotstraat,
, 2600 Berchem (Antwerp)
+32 3 377 49 33
sales-be@covolt.eu
