The three units are branches of state-owned electricity supplier Electrica.
The commencement of listing procedures was decided in the Government meeting held Tuesday, and it is part of agreements concluded with the International Monetary Fund.
The sale price will be decided in shareholder meetings held at each unit, based on broker recommendations.
Each of the three companies is 78% owned by Electrica, while investment fund Fondul Proprietatea (FP.RO) holds 22% stakes.
Electrica SA, which has a market share of 3% on the electricity supply segment, will cease to exist once its activity is transferred to Electrica Furnizare. In its turn, Electrica Furnizare will be sold by the end of October 2012, under agreements with the IMF.