The coal-fired power station at Cockenzie in East Lothian has been closed.
The station's huge chimneys are a well-known local landmark, but the station does not meet modern environmental standards.
ScottishPower wants to convert the plant to burn gas, rather than coal.
There have been no compulsory redundancies, with workers offered other jobs, redundancy or early retirement.
Bill Kelly, Cockenzie Power Station manager, said: "It was a hugely emotional moment for me. I have been here for 27 years.
"I'm an engineer to trade, but not an operational engineer. So was a big thrill for me for the guys to let me push the button."
Neil Clitheroe, ScottishPower's CEO of energy retail and generation, said it was an important day for the workforce and the local community.
He added: "It is the end of an era for ScottishPower and for the people at Cockenzie Power Station, who I would like to thank for all of their hard work and commitment over the last 45 years.
"Every man and woman who has ever been connected with the power station has played an important role in helping to keep the lights on in Scotland and across Great Britain.
"Cockenzie is one of a number of core power stations in Britain that are due to cease operations this year, and it is vitally important that we receive clarity from the Energy Bill to allow companies like ours to be confident in making investment decisions for a new generation of replacement gas power stations."
He added: "We have planning consent for a new gas-fired station here in Cockenzie, but like many other companies, we are unable to commit to new investment in gas generation until we fully understand how the market will work in the future."
Lang Banks, WWF Scotland's director, said: "The closure of Cockenzie coal plant marks an important milestone in Scotland's progression to a renewable energy future.
"Renewables now generate more of Scotland's electricity needs than either coal or gas and reduced emissions by over 10 million tonnes last year.
"There is no need for the proposed new gas plant to fill the space left by the coal station.
"The government's own energy policy shows Scotland doesn't need any new gas or coal to keep the lights on.
"A new unabated gas plant risks locking Scotland into high carbon electricity generation that threatens our climate targets and makes us even more reliant on volatile global gas markets."