100% RES scenario to improve energy security of R. Moldova is analyzed. Economic simulations are used. The paper shows that only about 70% of the demand could be covered directly from wind farms (WF) and photovoltaic (PV) energy sources (WPES). The remained 30% of energy (RE) - by energy storage system (ESS) with a capacity (kWh) of 32% from RE and a power (MW) of 87% from maximum power demand. As country doesn’t have its own hydro reserves, Li-ion batteries are considered for ESS. The investment in such SSE would exceed 3-52 times national GDP and that makes unrealistic 100% RES scenario for R. Moldova. As analysis showed, there are more than 1400 episodes within the year when energy to cover daily demand cannot be accumulated during 1 to 4 days. By reducing SSE capacity to a value equal to the daily energy demand and maintaining ESS power, it was found that the levelised tariff of WPES+ESS scenario exceeds, however, those of traditional scenarios. Only 5% of energy produced by WPES can be accumulated in such ESS, the remaining 25% - by importing night electricity, at negligible price in the calculations.