What energy costs do you have (electricity/gas/alternative heat source)?

That depends on so many conditions that you can't say for sure. It will be between 400 and 1000€. 100€ is already decent, since they probably also have a solar thermal system on the roof. What you don't know, however, is: Maybe the house is on the alp, in the shade, windows tilted open half the day, but 25°C comfortable temperature - then the 100€ advance payment would be quite cheap. Then there is also maintenance, chimney sweep, etc.

Actually, the house is located quite normally in the Osnabrück district, has a central ventilation system with heat recovery, etc.

And the thermostats are set to 20/21 degrees.

That's why the high consumption surprises me... but without details about the house, you probably really can't say anything.

But I would be happy if one or the other here would simply share their additional costs (electricity and heating (gas or electricity for air-water heat pump)) once with the rough details of their house.

Yes, then it really sounds unusually high. Air-to-water heat pump KFW55 165m², controlled residential ventilation with WR, €700 last year heating/DHW

Around 1200,- per year. Electricity and gas. Slightly more electricity than gas. Both providers eon in a combined tariff.

Move-in 2017
Location: Eifel (550 meters above sea level)
Built according to Energy Saving Ordinance 2016
160 sqm living area, 2 persons
Ground source heat pump + controlled residential ventilation

Heat pump electricity: 37 euros monthly installment
Household electricity: 39 euros monthly installment

However, we expect a refund for the heat pump electricity when spring slowly arrives from March.

160 sqm KFW55 with air-water heat pump/controlled residential ventilation and now 2.5 people
Move-in 2017
Temperatures in the house: 50% of the sqm (all-purpose room, bathroom) are at 23-24 degrees, the rest at 21-22

For the heat pump it is about 3000 kWh, trend declining
Household electricity about 3500-4000 kWh
How much that comes to in € everyone can now calculate themselves according to their preferences (1 or 2 meters, green electricity yes/no).