Buy a house with energy class H and not renovate much?

Where exactly do the consumption values from the energy certificate come from? Actual consumption from the last few years? If not, just ask for the bills.

Well, in the morning I ventilate the bedroom for 15 minutes by fully opening the windows. The house is just under €200,000 and has (for me, as a countryside dog sportsman) a great location. The consumption values from the gas suppliers of the current owner are calculated at only 180 kWh per m2 of gross floor area and absolutely affordable with an alleged indoor temperature of 23 degrees in winter and no nighttime setback due to fear of mold. It may of course also be that the heating costs are absolutely affordable and a major renovation (facade, photovoltaics, completely new roof, heat pump, etc.) is not worthwhile, and that one has a pleasant indoor temperature in the house without spending too much money on heating.

How big is the house? 180 kWh/m2 can be affordable for 100 m2 (the gas price here is just over 8 cents, so that would already be €130 per month), but it gets difficult at 300 m2.
And the gas price will rise. Will you have the financial opportunity to insulate it after all in the course of the next years?

P.S. Especially in the bedroom at night, it can get interesting. Night setback and half a liter of moisture that a person releases at night. Nobody airs out then either

Why not? At our place (and many I know), the bedroom window is slightly open at night. Almost all year round, even down to subzero temperatures.

The house is 115 m2 in size, the energy certificate (demand certificate) talks about a final energy demand of 320 KWH per m2. The bills I have been shown are (at a gas price of 9 cents) around €1900 (except 22 when the gas price boomed) and then one calculates a consumption of 180 KWH per m2, and that without insulated attic ceiling, insulated basement ceiling, and a supply temperature of 80 degrees at the heating boiler, whereby the masonry is said to have had an 8 CM air layer into which blown-in insulation was injected in 2017.

That is based on the assumption that the price remains at 9 cents. Is it still acceptable for you if the gas price rises to 15 or 18 cents? The proposed renovation measures are definitely good for now, relatively inexpensive, and offer relatively the most (price/performance).

Does hot water also run on gas? For us (four people), that accounts for about 1/3. So if fewer people live there in the future, it will be cheaper.

With this consumption, I would take the risk if I were you. A few optimization measures have already been mentioned. Yes, the gas price will probably rise (I just secured 6.9 cents per kWh...). But not infinitely, as long as 50% of households are heated with gas. And even if the price doubles, you will still be better off than spending 100,000 EUR more on another house.

By the way, what saved us about 2,000 kWh of gas:
* Less water consumption (water-saving shower head - lower the supply temperature for hot water).
* Do not run circulation all day and also switch off water heating occasionally.
* Programmable radiator thermostats (the cheap ones for 10 EUR - when I wanted to buy some in 2022, the "smart" ones were outrageously expensive).