The Bahraini owner of Energia here is plotting a sale of the Irish business in a deal certain to value it at more than €1bn.
Arcapita, a private equity group whose interests extend across a range of asset classes, has reportedly been sounding out advisers to line the Viridian energy arm up for a trade sale.
In Northern Ireland, Viridian owns Power NI, where it supplies electricity to about 610,000 homes and businesses.
In the Republic, Viridian owns Energia, which supplies electricity to the domestic and commercial market.
According to Viridian's latest annual report, Energia had 61,300 commercial customers at the end of March, most of them for electricity. It had 56,000 domestic customers, with 26,000 of those buying both electricity and gas from the company.
Energia's revenue fell to £893.5m (€1.2bn) in the last financial year from £1.01bn, while pre-exceptional earnings before interest, tax, depreciation and amortisation (EBITDA) fell to £65.1m from £70.8m.
Energia also owns two power plants in north Dublin.
On a group basis, Viridian generated revenue of £1.46bn in its last financial year, compared to £1.6bn a year earlier. Group pro-forma operating profit was unchanged at £77.1m. Industry journal 'Sparkspread', which first reported the planned sale, said that Arcapita ran a beauty parade of potential advisers this month.
A spokesman for Viridian declined to comment.
Last year, Arcapita, which bought then publicly-listed Viridian in 2006 for £1.6bn, had talks with JP Morgan about a possible stock market flotation of the energy business.
In 2010, Viridian sold its Northern Ireland electricity transmission and distribution business to the ESB for £1.2bn.
Arcapita filed for bankruptcy protection in 2012 in the United States as it sought to reorganise its finances. It had failed to refinance a $1.1bn loan that was about to fall due.
The Viridian group had managed to refinance its own balance sheet, receiving a €120m cash injection from Arcapita days before the bankruptcy protection was sought.
This year, Credit Suisse and Deutsche Bank led a €600m bond offering for Viridian that helped to cut the power firm's borrowing costs.
Earlier this year, Energia Renewables received a €125m loan from Nord/LB to fund the construction of a 95 MW wind farm project in Co Donegal.