Portugal has been supplied entirely by renewable energy sources including wind, hydro, and solarpower.
NGO Zero's president Francisco Ferreira was quoted by Independent as saying: "Portugal has been investing considerably in renewables, particularly in electricity, since this will be the main final energy within the next decades with the transition from fossil fuels in road transportation to electric vehicles."
Portugal relied considerably on coal and natural gas for its power supply and with this achievement solarpower is expected to play a larger role.
SolarPower Europe CEO James Watson was quoted by The Guardian as saying: "This is a significant achievement for a European country, but what seems extraordinary today will be commonplace in Europe in just a few years.
"The energy transition process is gathering momentum and records such as this will continue to be set and broken across Europe."
A similar milestone was reached in Germany, which met its energy needs through renewable resources for 24 hours on 15 May.