What amounts of additional co-generation and peak-up electricity could be produced by existing power generation facilities of UAB Vilniaus Energy in the event of possibility to store thermal energy in the hot water tanks were examined in this work. For this purpose, operating modes of equipment, thermal energy amounts necessary for storage, heat storage and output capacities, and other technical and technological aspects were examined. Technical possibilities to adapt the existing fuel oil tanks for hot water storage and investment demands were examined. Parameters of new hot water tanks and their indicative prices were also set. Considering the possible scenarios of the electricity market in Lithuania and the cost of heat storage, the potential payback of tanks upon change in the major affecting factors was estimated.