More nuclear power stations may need to be built in Wales as the UK's gas and oil stocks diminish, trade unionists have been told in Cardiff on Monday.
The TUC says policy makers need to face up to tough choices
The Wales TUC is staging a conference in the city to address the future energy needs of the nation.
Speakers have warned that failure to act now could spell disaster for workers, communities and businesses.
But Friends of the Earth Cymru says Wales' energy needs can be met through renewable sources.
The conference, entitled 'Could the Lights Go Out in Wales?' is being supported by npower and the Trade Unions for Safe Nuclear Energy (TUSNE).
Speaking ahead of the gathering at Cardiff's Angel Hotel, Derek Walker, the Wales TUC's head of policy and campaigns, said the aim was to outline the tough choices facing policy makers.
"The UK will soon become a net importer of gas and oil," he said.
"However, the sources of gas and oil will be from some of the world's most unstable countries where security of supply and price may not be guaranteed."
Mr Walker said there needed to be a diverse energy supply and, at this stage, nuclear energy should not be discounted as part of the solution.
"Global energy demand is likely to double over the next 50 years," he added.
"There is increasing doubt about whether renewable energy generation such as wind farms can meet our future energy needs, resulting in a potential energy deficit.
"Decisions on just how we fill that deficit will need to be made quickly and this conference will be a major contributor to that debate."
Among those taking part on Monday will be Malcolm Grimston, senior research fellow at the Royal Institute of International Affairs, who has argued the case for replacing the UK's retiring nuclear plants.
He said nuclear power currently accounts for just under 25% of the electricity generated in the UK and most nuclear stations will reach the end of their lives in the next 20 years or less.
Off-shore wind farms
"Unless replacements are ordered soon, the proportion of electricity generated in nuclear stations may fall to just 3% by 2020," he said.
But Neil Crumpton of Friends of the Earth Cymru told the Politics Show on BBC1 on Sunday renewable energy could meet all of Wales' electricity needs in the future.
"We can produce about 30% of Wales electricity by 2012 just with existing policies and off-shore wind farms in Liverpool Bay," he said.
"We have tidal lagoons in the Seven Estuary and Liverpool Bay than could generate more (electricity) than Wales consumes."