Will the stabilizer help to increase the voltage in the 380V network?

Good day! My question is: there is an electric boiler heating 12 kW 3 tena 4 kW each, connected individually in a private house with an area of ​​75 sq.m. So he does not have enough voltage to work, he heats it at 4 kW to 45 degrees barely barely. The line is stretched separately to the boiler and all the necessary electrics, RCDs, automatic machines, etc. stand in the shield, the voltage goes only to the boiler. There is a separate line for 220 V to the house. Question: Will the installation of Resanta 15 kW help me for a better and more adequate operation of the heating system? Thank.