There are calls for the Welsh assembly and UK governments to start planning future energy needs now, or face power cuts and job losses.
Wind turbines have become part of the landscape across Wales
Experts at the Wales TUC conference are expected to call for more balanced and sustainable energy sources.
An appeal not to rule out nuclear energy as an option is also expected to be made at the Llandudno event.
The conference is held as opponents to plans for 230 wind turbines off north Wales lobby Llandudno town council.
The UK will soon import more gas and oil than it exports and delegates at the TUC conference will be warned the UK could be at the mercy of international events unless other resources are established.
"The sources of gas and oil will be from some of the world's most unstable countries where security of supply and price will be out of our hands," said the union's Welsh general secretary Felicity Williams.
At the same time, she said demand for energy was "likely to double over the next 50 years".
Nuclear plants such as Trawsfynydd are being decommissioned
She added: "There is increasing doubt about whether renewable energy generation such as wind farms can meet our future energy needs.
"And the nuclear fleet, which provides 20% of our current energy and emits virtually no greenhouse gases, is in the process of being decommissioned.
"Decisions on just how we fill this massive deficit will need to be made quickly and this conference will be a major contributor to that debate."
The TUC conference is also set to investigate issues of 'cleaner' coal and greenhouse gas emissions.
Last month, the Welsh Assembly Government launched consultation on a scheme to give Wales "cleaner, more efficient energy production".
On Thursday, oil firm Marathon announced it would start drilling for gas 21 miles off the Pembrokeshire coast this autumn.
The £12m project off Milford Haven will be the first commercial drilling off Wales in 11 years.
The firm said that gas reserves, which were not commercially worthwhile years ago, are now more valuable because of the increases in energy prices.