People in Scotland are being urged to consider future energy needs before "the lights go out" in the country.
The Cockenzie plant is expected to within 10 years
Friends of the Earth Scotland (FoE) has held a conference in Edinburgh to debate long-term energy requirements.
The event, Keep the Lights On Without Warming the World, heard the views of experts from the coal, oil, gas, renewables and efficiency fields.
FoE Scotland chief executive Duncan McLaren said the next 20 years were crucial to the country's well-being.
The conference at the city chambers was told that Scotland's coal plants at Longannet and Cockenzie are likely to close within 10 years and nuclear power from Torness and Hunterston is likely to be phased out over the next 20 years.
Speaking before the conference, Mr McLaren said action should be taken to secure Scotland's future energy needs.
"We cannot just sit around until the lights go out, the debate and discussion needs to start now," he said.
"What we urgently have to consider is what will replace this capacity and how we will cut pollution but still keep Scotland's businesses running, our homes warm and people out of fuel poverty."
Scotland has an opportunity to become a world leader in the energy industry, he added.
"Wind, wave biomass, solar and tidal power all have massive potential in Scotland as long as we can resolve the complex challenges of investment, planning controls, system balance, pricing and regulation, to create effective markets and meet the Scottish Executive's ambitious targets," Mr McLaren said.
"We must start planning now to convert to a low energy, zero-carbon economy. We hope today's event is Scotland's first step on that road."
MP Martin O'Neill, chairman of the trade and industry select committee, was among the conference speakers.