Curtailing solar used to be a dirty word. A sign that clean energy was going to waste. But today, in markets with volatile or even negative prices, smart curtailment is a sign of maturity. It’s a way to preserve value, participate in multiple energy markets, and improve return on investment.
To do this right, however, you need more than just a solar installation. You need a solar curtailment stack: a set of integrated capabilities that allow you to forecast, decide, and act — fast.
In this blog, we break down the four essential layers of that stack.
1. A fitting injection contract with your energy supplier
Your energy contract determines what’s even possible.
Many solar producers are constrained in terms of optimization potential due to their contract, preventing them from pro-actively anticipating market signals like negative prices or imbalance opportunities.
With the right contract setup, you get:
- Smart nomination, projecting how much to inject before the day-ahead market clears, based on market price forecasting
- Pass-through pricing, seeing true day-ahead and imbalance prices without hidden margins
- Individual balancing optimization, focusing on opportunities at the EAN level, not just for the supplier’s total pool of customers
"If you want to steer, you need market access. And you need a supplier that lets you nominate in a smart way."
“We don't optimize for our own pool, we optimize for the customer.” - Elias Vandeputte, Flexibility Manager BEE
This is step one. Without it, the rest of the stack doesn’t matter.
2. Forecasting and optimization software
Once your contract allows for flexibility, you need to know when and how to act.
That’s where forecasting and optimization software enters.
At Companion.energy, we specialize in this layer of the stack. Our platform:
- Forecasts behind-the-meter production, consumption, and market prices (day-ahead and real-time)
- Optimizes across multiple curtailment and injection scenarios to find the most profitable one
- Triggers curtailment decisions automatically
- Makes realized value visible — in euros, not just kWh
Example: On Mother’s Day in Belgium, the day-ahead price dropped to -463 €/MWh. We predicted this and nominated no solar during negatively priced hours the day before. But, when imbalance prices turned positive in real-time, we resumed production at a profit. That’s the power of having the right tools and foresight.
3. A reliable local EMS
Software only creates value if it can act on the asset. This requires robust local connectivity. This layer includes:
- A gateway or PLC (often referred to as a local EMS) that can interface real-time data and receive steering commands
- Reliable communication between cloud and site
- Fail-safes for fallback behavior if curtailment fails
If your site can't respond quickly or correctly, you're either injecting at a loss or missing market upside.
That’s why hardware and communications reliability is a key (and often underestimated) part of the curtailment stack.
4. A curtailable solar installation
At the base of it all: your solar asset. But not all installations are created equal. To enable curtailment, your system must:
- Support dynamic control of inverters
- Have up-to-date telemetry and monitoring
- Be correctly configured to avoid conflicts with grid protection or subsidy rules
In other words, a “smart solar” setup is more than just panels on a roof. It’s a controllable, visible, and monetizable asset.
Integrated vs. modular: choosing the right approach
When building your solar curtailment stack, companies typically face a strategic choice: going for an integrated solution or assembling their own stack by combining best-in-class building blocks from multiple partners (e.g., a separate EMS vendor, software provider, and energy supplier).
An integrated approach offers lower complexity, with a single partner handling coordination across contract, software, and hardware. This can be ideal for companies seeking speed, simplicity, and clear accountability. On the other hand, building your own stack offers maximum freedom of choice. This enables you to select each layer based on specific needs, legacy systems, or preferred technologies.
There’s no one-size-fits-all answer.
The right choice depends on your internal capabilities, risk appetite, and the degree of control you want over your energy operations.
Ready to build your stack?
A performant solar curtailment stack offers:
- Proactive, value-maximizing decisions
- Transparency across the chain (contract, software, data, results)
- Aligned incentives between producer, supplier, and optimizer
Companion.energy works with innovative suppliers and hardware partners across Europe to help companies take control of their solar assets.
We help you go from contract to control, and make every megawatt count.
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The Curtailment Club
This blog is part of our series called “The Curtailment Club”, where we will dive into the drivers, misconceptions, and solutions behind renewable energy curtailment over the coming months.
