When the off switch is flicked at Longannet in Fife at 3pm, the last of the station’s four generating units will be permanently shut down.
The move signals the end of coal-fired electricity generation in Scotland, as the country’s largest and last remaining coal-fired power station is “desynchronised”.
Longannet was the largest power station in Europe when it came online in 1969, capable of producing 2,400 megawatts of electricity for the grid.
It took eight years to build and powered an average of more than two million homes annually during its working life. The plant operators said today’s closure marks a “sad day” for everyone at Longannet and the end of the coal age in Scotland.
“Longannet has contributed more electricity for the national grid than any other power station in Scotland’s history, and it is a sad day for everyone at ScottishPower,” said Hugh Finlay, generation director at plant owner ScottishPower.
“Coal has long been the dominant force in Scotland’s electricity generation fleet, but the closure of Longannet signals the end of an era.
“For the first time in more than a century, no power produced in Scotland will come from burning coal.”
Environmentalists have expressed sympathy for workers who may lose jobs but welcomed the closure of the plant as a major step in the battle against global warming.
They say the switch-off heralds the “beginning of the end” for fossil fuels north of the border.
Dr Richard Dixon, director of campaign group Friends of the Earth Scotland, said: “For the first time in at least 115 years there will be no coal being burnt to make electricity anywhere in Scotland.
“For a country which virtually invented the Industrial Revolution, this is a hugely significant step, marking the end of coal and the beginning of the end for fossil fuels in Scotland.”
He added: “Coal is the dirtiest of the main fossil fuels and in a peak year Longannet was producing 10 million tonnes of carbon dioxide – around a fifth of all Scotland’s climate change emissions.”
The closure will see “the single biggest reduction in Scotland’s climate change emissions ever”, he said.
WWF Scotland director Lang Banks said the shut-down was “inevitable” as part of the global shift towards more environmentally friendly forms of energy generation.
Many of Longannet’s 236 staff have been redeployed, and early retirement and redundancy packages have also been offered. Around 45 will remain on site to carry out decommissioning works.
Mr Finlay expressed thanks to staff for keeping Longannet running safely over its life.
No decisions have yet been taken on the future of the site.