Energy efficiency is an important factor of economic competitiveness and is a constant concern to European and national level. A very actual problem is the power quality, for all consumers. Continuity of supply but also the voltage dips are factors affecting the smooth operation of facilities and equipment for all consumers. An energy storage unit consisting of supercapacitors fitted to a domestic consumer is able to offer a quality power flows without changes or interruptions. An energy storage unit based on supercapacitors not only provides continuity of supply, but also filters any power fluctuation intensity (with auxiliary devices, inverter, filter), ensuring additional protection to any electronic system. Autonomy depends on the device size and on consumption level. There are well known supercapcitors' advantages in dynamic applications (very long life cycle, fast loading, power pulse, etc), but the discharge process is short. Batteries have high energy density but low power, while supercapacitors can provide high power, but for a short time. Therefore, the performance of a storage system based on supercapacitors can be improved by using them in combination with batteries.