The lights of Paris dimmed for five minutes on Thursday in a nationwide "lights out" campaign, aimed at raising public awareness over global warming.
National consumption fell by over 1% during the switch-off
The Eiffel Tower, lit by 20,000 bulbs, also went dark at 1955 (1855 GMT).
During the switch-off, the power grid operator RTE observed a fall of 800 megawatts, representing just over 1% of France's total consumption.
It comes a day before the release in Paris of a major report warning of humanity's role in climate change.
The report by the Intergovernmental Panel on Climate Change is expected to say that climatic changes seen around the world are "very likely" to have a human cause.
'A real issue'
Environmental campaigner Anne Briangault told the BBC that people would like to be involved in tackling climate change but needed advice on what they could do.
"... we are explaining they can do things, they can switch off some lights but it's not enough. Politicians have to make actions too," she said from the base of the Eiffel Tower.
Some experts warned the switch-off could backfire, arguing that more energy could be consumed because of a power spike when lights were turned back on. However, no problems were immediately reported.
Several other European cities also staged symbolic blackouts. In Rome, the lights of two of its celebrated monuments, the Colosseum and the Capitol, were turned off.
In Spain, Madrid's Puerta de Alcala arch was plunged into darkness.
In the Greek capital, Athens, lights illuminating several public buildings - including the parliament, city hall, and the foreign ministry - went dark.