The ESB has announced that it will close two power stations in the midlands.
The West Offaly and Lough Ree power plants will cease operations at the end of 2020.
The ESB had submitted an application to An Bord Pleanála last year, seeking planning permission to transition the West Offaly plant from peat to biomass over a number of years - starting in 2020.
This planning application was rejected in July of this year.
Since then, the ESB says it started a review of the options for both stations.
In a statement, the utility said: "Having considered the key planning, environmental and commercial issues associated with peat and biomass, regrettably there is no viable business model beyond 2020.
"Therefore both stations will cease generation of electricity at the end of December 2020.
"Given our long history of power generation in Shannonbridge and Lanesboro, this is a matter of significant regret for ESB.
"ESB very much appreciates the commitment of our staff and the support of the broader community over many decades during which ESB, in strong collaboration with Bord na Móna, played a key role in the development of the economy in the midlands."
The ESB adds that it will now begin the process of engaging with staff and stakeholders to prepare for an orderly closure.
The Government has recently announced the creation of a €6m transition fund for the midlands.
In light of the closure of Lough Ree and West Offaly, the ESB says it will make an additional contribution of €5m to this fund.
In July, the company said it was laying off around 150 workers due to the closure of the Lough Ree power plant.
Last year it announced the closure of 17 of its 62 active peat bogs.
The company was moving to speed up its decarbonisation efforts, and work towards more renewable energy efforts.
Sinn Féin's environment spokesperson David Cullinane slammed the Government and ESB.
He said: "The news that the ESB is to close two power stations in the midlands without any alternative arrangements in place is nothing short of a betrayal of the workers and their local communities.
"Both the ESB and the Government promised that alternative measures and a just transition would be in place before any decision to close would be taken.
"That, it appears, is now off the table, delivering a devastating blow to the 80 ESB workers affected and the 1,000 Bord na Móna workers who rely in no small measure on the plants.
"The Government must convene a just transition taskforce as a matter of urgency."