The activists climbed a cooling tower at the Agios Dimitrios plant in Kozani, northern Greece, that belongs to Public Power Corporation (PPC), the country's main electricity provider.
They spent 14 hours on the tower at a height of 130 metres (425 feet) and painted "Go Solar" on its side before police arrested them.
"We chose the largest and most polluting lignite station in the country, responsible for nearly 15 per cent of national carbon dioxide emissions," said Takis Grigoriou, energy supervisor for Greece at Greenpeace.
The group said the operation was part of a worldwide mobilisation as representatives of nearly 200 nations try to reach a deal to curb global warming at a UN conference in Paris.
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Greece is trying to meet a renewable energy quota -- 20 per cent of national electricity production -- by the end of the decade and has pledged to boost solar and wind power generation.
Yet around half of the country's electricity production still comes from coal-fired plants, and PPC is Greece's single largest offender in carbon dioxide emissions.
Today the organisation said it had sent the government a 10-year plan to encourage solar energy use in households.
"To meet the target of a temperature rise of no more than 1.5 degrees Celsius... We need 100 per cent renewable energy by 2050 globally," Grigoriou said.