People in Pembrokeshire are being consulted on plans for a new gas-fired power station.
Qatar Petroleum, Exxon Mobil and Total Gas and Power Ventures, who are behind the South Hook CHP project, want to build it on the site of its liquified natural gas plant at Milford Haven.
South Hook CHP says the development would be "one of the most efficient low-carbon power stations in Europe", and would generate up to around 500 megawatts.
Waste heat from the site would be used in the adjacent liquified natural gas plant, a move that the company claims would make the power station 30% more efficient than "the very best of the existing power stations".
Campaigners are concerned about any environmental impact on the local area.