Connecting a 9 kW electric boiler with replacement of electrics in a private house

Julia asks:

Good afternoon. There is a summer cottage, to which 4 kW electricity is supplied. The electrics are all divorced and working. Now we want to connect an electric boiler for heating, with a capacity of 9 kilowatts. The house is 2-storey, foam block, total area about 115 m2. We realized that for this we need to increase the power up to 15 kW. Please tell us how to correctly make the electrical installation in this case?

Is it possible to leave the current wiring (it is not designed for 3 phases), reconnect it to a new panel and make a direct exit to the boiler from it?

Hello! In any case, you need to sort out the shield, replace the introductory AB.
Throw a separate line with a separate AB to the boiler.

First, prepare documents for requesting technical conditions for increasing power and connecting 3 phases. Next, a project for an installed power of 15 kW, then buy a meter, most likely a direct connection. If possible, then it is better to rebuild the shield into 3 phases, if it does not work, then talk to the energy company, maybe they will start 3 phases purely for the boiler and that's it