REN Prepares Portugal’s Electricity System for Solar Eclipse Impact on Power Generation

REN Prepares Portugal’s Electricity System for Solar Eclipse Impact on Power Generation

(IN BRIEF) REN – Redes Energéticas Nacionais is preparing Portugal’s National Electric System for the effects of the nearly total solar eclipse expected on 12 August 2026. The eclipse is forecast to reduce centralised solar generation by around 450 MW, equal to about 45 percent of projected solar output during the affected period and around 7 percent of electricity consumption. During the event, solar generation could fall by as much as 35 MW per minute, requiring REN to mobilise additional hydroelectric and/or thermal reserves to maintain balance between supply and demand. The impact is expected to be moderated by the fact that the eclipse will occur in the late afternoon, when solar output is already declining, although it will coincide with rising demand toward the evening peak.

(PRESS RELEASE) LISBON, 11-Aug-2026 — /EuropaWire/ — REN – Redes Energéticas Nacionais has been preparing Portugal’s National Electric System for the expected effects of the nearly total solar eclipse scheduled for 12 August 2026.

The preparation work has been carried out in close coordination with other European electricity transmission system operators.

The eclipse is expected to reach magnitudes of between 92 percent and 100 percent in mainland Portugal, with the strongest effect anticipated in the north of the country.

The phenomenon is expected to occur between 6:30 p.m. and 8:30 p.m. and will temporarily reduce solar power generation.

REN estimates a loss of around 450 MW of solar generation during the event.

This represents approximately 7 percent of electricity consumption and 45 percent of the National Electric System’s forecast solar production for that period, based on average figures.

Taking into account the projected solar production peak, the overall impact of the eclipse is estimated at around 15 percent.

The figures refer only to centralised solar generation recorded and measured by REN.

They do not include other solar generation linked to certain Self-Consumption Generation Units, which will also influence electricity demand.

REN is also estimating this effect and incorporating it into consumption forecasts for the day in order to reduce and mitigate unexpected impacts in real time.

During the eclipse, the maximum loss of solar generation is expected to reach 35 MW per minute.

To help manage the impact of this reduction on the balance between generation and consumption in the National Electric System, as well as deviations in the electricity interconnection with Spain, additional reserves will need to be mobilised.

These reserves are expected to come from hydroelectric and/or thermal generation.

Preparations for the eclipse have been coordinated with other European transmission system operators, particularly through the Short-Term Adequacy service.

This service supports the balance between electricity generation and consumption over a seven-day planning horizon.

Across the European synchronous area, the total loss of production linked to the eclipse is estimated at approximately 9,700 MW.

REN said the impact in Portugal will be less significant because the eclipse will occur in the late afternoon, when solar generation is already declining.

However, the event is still expected to produce a sharper-than-usual reduction in solar generation.

This will coincide with rising electricity consumption as the day moves toward the late afternoon and early evening peak demand period.

In July, solar generation supplied 19 percent of electricity consumption in Portugal.

It was the first month in which solar power became the leading renewable technology in the national grid compared with other renewable sources.

During the same month, hydropower supplied 16 percent of consumption, wind power supplied 13 percent, and biomass accounted for 5 percent.

REN said Portugal has maintained a sustainable path in the progressive integration of domestic renewable energy sources in recent months.

This has been supported by successive records in renewable electricity production, while maintaining the main objectives of security of supply and quality of service in the National Electric System, even under challenging operating conditions.

Through its preparation for the solar eclipse, REN is seeking to ensure that Portugal’s electricity system remains secure, balanced and resilient during a temporary but significant reduction in solar generation.

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SOURCE: REN – Redes Energéticas Nacionais