The increase of production from wind power plants and photovoltaics with changing market conditions are changing the energy system as we have known. Estonia has set a target to increase the consumption from renewable energy by 2030 to 50%, which would mean that there is a need for about additional 2.3 TWh of electricity generated from renewables by 2030. The maximum flexibility of the existing energy system in integration of renewable energy is not yet analyzed. The EnergyPLAN software is used in the study to determine what is the technical-economical limitation of additional wind and photovoltaic that can be added to the system. The results demonstrate despite the additional renewable energy generation the conventional oil shale based power plants which are mostly influence by the CO2 price. Even when the Estonian 2030 renewable energy targets would multiple the renewable energy production, because of the high CO2 price Estonia would transform to electricity importing country.