Small scale.
Zero imbalances.

A small generating unit places its energy in the day-ahead market and is exposed to the gap between what it scheduled and what it produced. That imbalance has no price of its own: it settles at the cost of the balancing energy the system had to activate in that quarter-hour. When the system is expensive, the imbalance is expensive.

The cost is material and it is not manageable at this scale. A 1 MW producer has no market desk, no dedicated forecast, and no balance perimeter in which its imbalance can be offset by another plant’s.

Regulation charges in Portugal rose from €7.99 to €13.01/MWh between 2023 and 2025, more than 60% in two years. The system services market went from €550 M in 2023 to €1,350 M in 2025. Source: REN.

Gesto Comercialização brings the unit into its balance perimeter and takes on the imbalance. The producer receives a guaranteed minimum revenue and stops seeing imbalance on its account.

The payment reference is deemed energy — what the asset would have delivered, measured at the pyranometer installed on site, not the energy actually injected.

• No exposure to negative prices. In hours when the market pays not to produce, the decision to stop is ours and the producer is still paid on deemed energy.
• No loss from voluntary stops. Stopping is our management decision and does not affect what the producer receives. The same applies to a curtailment imposed by the grid operator.
• Guarantees of origin restored. The guarantees belong to the producer and are issued on real energy. Whenever it injects less because of our decision or a grid curtailment, we restore them.
• Fortnightly payment. Without waiting for the system settlement cycle.
• Fixed fee, no sharing. The value here is avoided cost, not new revenue. The price follows that design.

1 · Weather station. A pyranometer is installed on site, with telemetry. The sensor is the billing reference. On larger plants, sensor redundancy.

2 · Conversion function. The relationship between measured irradiance and output is fitted to the plant’s own history. It becomes independent of technology and equipment brand.

3 · Monthly recalibration. The function is recalibrated every month, using only hours with no setpoint. The coefficient in force appears in the monthly report. The calculation can be reproduced by the producer.

A physical pay-as-produced PPA gives the buyer a right to the energy physically produced. If we reduce injection, the producer is in breach. Under that arrangement we cannot honour the contract.

There are two ways out. Extend the deemed generation clauses the PPA already has for grid curtailment to market-driven reduction — the buyer loses no expected value. Or work only on the uncontracted share, which most PPAs leave.

Without remote control capability, and without enough production history to fit the conversion function, the imbalance returns to the producer.