Nearly 250 jobs have been safeguarded at a power station in the Vale of Glamorgan by a decision to install £100m of anti-pollution technology.
The revamp will cut the plant's sulphur emissions from 2008
Energy firm Npower said the sulphur emissions cut at the plant would secure its future for least 10 years.
The power station, which produces about a third of the electricity output for Wales, is supplied by Tower Colliery.
Objectors called for it to be closed when the plans were revealed in October 2003 and approved 10 months later.
Npower has committed itself to installing new environmental technology at the plant, with the aim of cutting sulphur emissions from the coal-burning furnaces by up to 90%.
The project is scheduled to be ready by early 2008 when a new EU directive on emission controls takes effect.
This investment is set to secure many more indirect roles in related industries in south Wales, such as Tower Colliery, the private deep mine at Hirwaun, which is a major coal supplier to the plant.
Aberthaw Station Manager Clive Smith said: "This investment will not only improve our environmental performance, it will also secure the future of the power station for at least the next 10 years.
"We are consulting and working with the local community and other interested parties to ensure there is minimal disruption to the local area and that everyone is informed of the ongoing plans."
However, people living near the plant called for its closure when the prospect of the revamp was made known in 2003.
They submitted a 900-signature petition against the proposals and called for the harbour on which the power station is built to be redeveloped with a new marina and tourism resort.
But Geoff Davies, managing director at Tower Colliery, said the coal industry in south Wales would be delighted to know that Aberthaw was to continue operating to 2018.
"Aberthaw is a major energy producer. Tower Colliery and Celtic Energy supply it with over a million tonnes of coal a year," he said.
"It's very good news, and with all the environmental changes coming about, this will enable Aberthaw to comply with legislation for the next 15 years."