Solar power output set to fall during eclipse

Published on 10/08/2026 - 16:38 GMT+2 Portugal's grid operator Redes Energéticas Nacionais (REN) expects it will have to tap additional energy reserves to offset the loss of solar power generation caused by Wednesday's eclipse. ADVERTISEMENT ADVERTISEMENT In the statement REN published on its website this Monday (source in Portuguese), the company says that "additional reserves from hydro and/or thermal generation will have to be mobilised" to mitigate the impact the phenomenon will have on the balance between energy consumed and generated in the National Electricity System (SEN), as well as the deviations the eclipse will cause in the interconnection between the Portuguese and Spanish grids. In neighbouring Spain, the eclipse will be 100% in a large part of the territory, while in Portugal it will be "almost total", ranging from 92% in the Algarve to 100% in the municipality of Bragança. The village of Guardamil is considered the best place in Portugal to see the eclipse in full. According to REN's statement, the phenomenon, which will occur between 18:30 and 20:30 on Wednesday 12th, "will lead to an estimated loss of solar generation of 450 MW", which will represent around 7% of consumption and 45% of the solar output of the National Electricity System forecast for this time slot (average values). REN further indicates that "compared with the peak solar output forecast, the impact of the eclipse is estimated at around 15%". For these figures, REN considers only centralised solar production and that recorded/measured by the company, excluding the solar energy generated by households for self-consumption. However, the impact that the drop in this household production will have on demand is factored into the consumption forecasts for that day. The company says that "preparations for this event have been carried out in coordination with the other European transmission system operators, in particular through the Short Term Adequacy (STA) load-coverage assessment service, which ensures the balance between electricity generation and consumption over a seven-day horizon". At the level of the European synchronous area, REN says the approximate loss of generation is estimated at 9,700 MW. REN also points out that the phenomenon will occur in the late afternoon/early evening, a period when solar power generation is already declining, and so the impact will be smaller. Solar power generation in Portugal reached an important milestone in July, the first month in which this energy source was the most used, accounting for 19% of consumption. Renewable sources represented 53% of total energy consumption.