Single-family house - 18,000 kWh in two years - what could be the problem?

We (duplex) handle the ancillary costs ourselves. Each party has 3k household electricity and pump 4K. Thus 20k in 2 years! One must not forget that the pump heats hot water and heating. Each apartment has its own meter from the city. The pump also has one (HT/NT), the consumption here is split via the heat meter in the apartment.

oh sorry guys, didn’t get a notification that it continues here.... I will take a look at your answers later and write something about it