TenneT prepares Dutch grid for 1.3 GW solar drop during 12 August eclipse

Dutch transmission system operator TenneT is preparing the Netherlands' electricity network for a partial solar eclipse on 12 August 2026 that it expects to reduce solar generation by up to 1.3 GW^[1] - a drop it describes as manageable within normal operational capabilities.^[1]

What the eclipse does to the Dutch grid

The maximum eclipse over the Netherlands will occur at around 20:10 local time, when an estimated 87% to 89% of the sun will be obscured depending on location.^[1] TenneT says the expected reduction is equivalent to roughly 10% of peak electricity demand in the Netherlands.^[1]

The evening timing is a mitigating factor. Solar panels already generate less electricity in the early evening than at midday, so the eclipse compounds a decline that would be happening anyway.^[1] The real operational challenge is not the volume of lost generation but the speed of the ramp: output falls and then recovers across a wide area within a compressed window, requiring flexible plant to respond quickly.

TenneT is coordinating with market participants and neighbouring operators ahead of the event.^[1]

The European picture

The Netherlands is one node in a continent-wide balancing exercise. Under clear-sky conditions, ENTSO-E estimates that photovoltaic output across Europe could fall by up to 9.7 GW, with the generation pattern shifting rapidly between 19:15 and 21:30 CEST. Spain and Germany are expected to experience the largest reductions.

• Spain: Red Eléctrica expects up to 5 GW of solar capacity to be lost - around 13% of typical peak demand on a Wednesday in August.
• Germany: The four German TSOs (50Hertz, Amprion, TenneT, TransnetBW) forecast a reduction of around 2 GW against an installed base of 125 GW of photovoltaic capacity.
• Great Britain: NESO forecasts a drop of roughly 700 MW, though it considers up to 1.3 GW possible.

The eclipse marks the first total solar eclipse over mainland Europe since 1999, arriving over a solar fleet far larger than anything operators managed then. The EU had approximately 406 GW of installed solar capacity at the end of 2025.

How operators are responding

ENTSO-E activated a dedicated task force to coordinate preparations and facilitate information exchange among its 40 member TSOs across 36 countries. Specific measures include:

• Briefing control room operators in advance to ensure heightened awareness
• Issuing updated photovoltaic generation forecasts to local system operators in real time
• Avoiding planned grid outages during the eclipse window to maximise operational flexibility
• Alerting market participants to the expected generation reduction

Hydroelectric plant, batteries, and fast-response gas units are the primary tools for covering the temporary shortfall. The eclipse's predictability - its timing calculable years in advance - is the key difference from an unplanned generator trip, which can remove large volumes of capacity with little warning.

What to watch

Cloud cover is the principal variable that operators cannot control: heavy overcast would reduce the eclipse's grid impact significantly, while clear skies across the Netherlands and Germany would push the drop toward the upper end of forecasts. TenneT has not indicated any need for emergency measures, but the event will serve as a live calibration of how well Europe's expanded solar fleet and its balancing tools handle a fast, synchronised generation swing - useful data ahead of a second eclipse expected in 2027, which is projected to arrive closer to midday when solar output is at its peak.