The changes in energy sector - such as wide use of intermittent generation, feed in tariffs, market mechanisms implementation - influence the running manner and role of conventional power plants. The operation at base load is shifted to operation in cycling modes. Due to the variability of intermittent energy sources the conventional power plants additionally should provide the secure supply of energy, maintain the parameters of electric network and operate according to the fluctuations of electricity price. The use of heat storage tank can adapt the operation manner of conventional power plants to these changes by decoupling the production of electricity and heat energy. Compared with other countries in Europe the intermittent energy sources are limited in Latvia. So the installation of heat storage system at Riga CHP - 2 plant can adapt its operation to situation at electricity market with the gain of additional profit.