Quick answer
Negative electricity prices occur when more power is produced than consumed during sunny or windy hours. In Belgium they occurred for hundreds of hours in 2025, and their number rises every year. For businesses this means: injecting power then costs money instead of earning it, but those who can charge or consume at those moments are rewarded — a battery does that automatically.
How can a price be negative?
On the day-ahead exchange (EPEX SPOT), a price forms every hour through supply and demand. Solar panels and wind turbines have near-zero marginal costs and keep producing even when there is no demand. When supply exceeds demand, producers bid below zero to keep delivering — the price turns negative.
In Belgium and Germany this happened for hundreds of hours in 2025, mainly on sunny weekend afternoons between April and September. The trend is accelerating: every additional MW of solar capacity increases the chance of negative midday prices.
What does it mean for a business with solar panels?
On a dynamic injection tariff, you pay net to put power on the grid during negative hours. On a fixed injection tariff, the average fee declines structurally because suppliers price in the negative-price risk. The conclusion is the same: uncontrolled injection is worth less and less.
- Curtailment: temporarily scaling back or switching off the installation during negative hours.
- Shifting consumption: running processes, cooling or charging precisely at those moments.
- Storage: keeping the production in a battery to sell or use later.
What does it mean for a business with a battery?
For a battery, negative prices are not a threat but a revenue source. The battery charges when the price dips below zero — you are paid to charge — and discharges during the expensive evening peak. That spread is the core of dynamic arbitrage.
In our own hybrid portfolio we see that negative-price hours coincide almost perfectly with peak solar production. A battery behind the meter therefore solves two problems at once: it avoids costly injection and it charges for free or against compensation.
Negative prices in numbers
| Situation | Without battery | With battery + control |
|---|---|---|
| Injection during a negative hour | You pay to inject | Production is stored |
| Consumption during a negative hour | Coincidence — usually no consumption | Battery charges against compensation |
| Evening peak (6–9 pm) | Expensive grid offtake | Discharge from your own storage |
| Annual injection revenue | Structurally declining | Less injection needed |
What can you do today?
First check which injection tariff you are on and how many hours you effectively injected at negative prices last year — your supplier or grid operator can provide that quarter-hourly data. Then it pays to simulate what a battery or smart control would have done with those hours. CleverNett runs that simulation free of charge based on your interval data.
Frequently asked questions
How often do negative electricity prices occur in Belgium?
In 2025 there were hundreds of hours with negative day-ahead prices, mainly on sunny weekend afternoons. The number rises structurally as more solar and wind capacity is added.
Do I really pay to inject electricity?
On a dynamic injection tariff: yes, during negative hours. The exchange price is negative then and is passed through. On a fixed tariff you do not pay directly, but your supplier prices the risk in through a lower fixed fee.
Are negative prices bad news for solar panels?
They make uncontrolled injection less profitable, but change nothing about the value of self-consumption. Every kWh you consume or store yourself still saves you your full purchase price. With a battery or smart control, solar remains an excellent investment.
Can I switch off my solar park during negative prices?
Yes, that is called curtailment. Modern inverters can automatically scale back based on a price signal. It beats paying to inject, but battery storage is usually more valuable because the energy is preserved.