Additional costs KfW55 experiences

50 euros just for heating + hot water is probably completely normal. No matter how much you insulate, hot water always costs the same. The total ancillary costs can be roughly estimated for a new building at 2-2.5€/m² living space (including a few euros saved for small cosmetic repairs). With your estimated 130m, that's about 250-300€/month including, of course, only a very rough estimate since no one knows if you have a sauna in there, etc...

our additional costs for our single-family house with 125 sqm amount to:

418€ property tax
197€ wastewater (73 m³)
120€ fresh water
708€ internet 100mbit
600€ for gas
780€ for electricity (3500 kwh)
139€ for garbage (including large black bin, organic, paper, yellow)
261€ building insurance including elemental
216€ household insurance
110€ chimney sweep
210€ GEZ penner...
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3789€/year : 12 = 313.25€ = 310€/month

the heating costs are completely irrelevant and don’t even make up 1/6.

Yes, sorry but 210€ a year for nothing is really quite outrageous. I pay hardly more for Sky. At least there you get Bundesliga live and current series for the money...

The value seems very low to me now, which heating system are you assuming? For most, I see more like 40-50 € on average, although that is still cheap.

I have 48 euros/month (this year it will be about 20% less, warm winter) for 134 usable area / 108 WF. Gas. KFW70. Heating / hot water without auxiliary energy (electricity).

I still buy gas comparatively expensive at 6.3 ct/kWh. And I am cold-blooded, meaning I get cold quickly, so it’s already 21.5 - 22 degrees here at home.

A KFW-55 should generally be cheaper. I estimate more like 30-35 euros/month based on gas.

Considering all costs, even heating/hot water with a KFW70 doesn’t make much difference anymore. Property tax and so on are higher costs.

The heating cost differences between a KfW70 and KfW55 house are actually not particularly significant. It is more of a calculation game. As I already said on page 1, the costs for hot water are always very similar because the insulation cannot be taken into account at all (except for the insulation of the boiler and the energy carriers used to heat the water). Heating the house does not cost particularly much and does not result in any real significant differences. Whether you heat 10€ more or less per month does not make the difference between "building" or "not building." I have already listed the ancillary costs a few posts above, and they also apply as a tenant. (Some costs are just hidden under the landlord’s ancillary costs there - but you have to pay all of them anyway... (water/sewage anyway, garbage too, property tax too, building insurance too, and you pay the rest yourself anyway (heating depending on the situation)...))