The ESB's Moneypoint power station - the biggest in the country and which cost more than €1.2bn to build and upgrade - is now valued at nothing, the Irish Independent has learned.

The entire value of the massive station has been written down by the semi-state company after it impaired the value of a number of generating assets last year.

The coal-powered station on the Shannon Estuary in Co Clare was commissioned in 1985 and was built at a cost of about £700m (€889m). It was one of the country's single biggest capital projects ever.

It was retrofitted in 2008 to reduce harmful emission of nitrous oxide and sulphurous oxide at a cost of €355m.

The ESB revealed this month that it incurred non-cash impairments of €276m after writing down the value of some of its generating assets in Ireland. That included a €142m impairment in relation to Moneypoint.

The ESB, whose CEO is Pat O'Doherty, said it took the "prudent decision" to impair the its generating assets based on the estimated impact on projected revenues from the introduction of the new Integrated Single Electricity Market in May this year, and lower wholesale electricity margins.

ESB chief financial officer Pat Fenlon confirmed that the book value of Moneypoint on the ESB balance sheet is now zero.

"The €142m is more or less writing the book value off," he told the Irish Independent.

Mr Fenlon said that the main part of the asset value in Moneypoint that had remained on the books related to the 2008 retrofit that ensured the power plant met new environmental controls.

That resulted in nitrous oxide emissions falling by 54pc, and sulphurous oxide emissions declining 71pc.

Moneypoint consists of three, 305-megawatt steam generating boilers and its maximum power output is the equivalent of about 20pc of the electricity demand in the Republic of Ireland. It uses about two million tonnes of coal a year.

Despite being environmentally unfriendly, it remains an important part of Ireland's energy infrastructure. However, it's likely to be decommissioned in the next decade or so.

"That 2025 to 2030 period is what we're aiming for," said Mr Fenlon.

The Energy Institute, a professional organisation for the energy industry in Ireland, has previously pointed out that even if was economically feasible to convert Moneypoint to burning gas, Ireland's power system would become too dependent on imported gas.

The ESB previously touted the long-term possibility of Moneypoint being converted to a nuclear power station.

However, public opposition means it's highly unlikely that this would ever succeed.

Irish Independent