Q Energia has two massive power plants in Huntstown in north Dublin, which are capable of providing one-fifth of the country's electricity. It is also a huge user of wind-generated power.
Its parent company is Northern-Ireland based Viridian, which in turn is owned by Bahrain-based investment firm Arcapita.
Energia supplies gas and electricity to around 65,000 businesses in Ireland.
In Northern Ireland, Viridian has around 80pc of the residential electricity market.
It is the first player to enter the domestic energy sector here in years.
The move comes after it was revealed that families are paying more than €450 a year extra for their gas and electricity compared with just two years ago.