Energy efficiency class!?

Hello,

I am a complete beginner in the topic of house building/purchasing and have a question that is presumably easy to answer:

- I often see somewhat older, partially renovated properties that have the class G, H, etc., and a value between 250 and 300.

I know that the calculation is probably somewhat vague or difficult, etc., but I absolutely cannot interpret whether an A house basically costs almost nothing and is also a total extreme, or if values beyond 250 are simply totally ridiculous...

Does anyone have a tip?

the value initially shows very little and the scale is set up very pessimistically. even well-insulated new buildings are already in the yellow range on the scale.

i don’t have the value for Kfw55 (good "standard new building") at hand right now, but it should be around 50-60. a top renovated older building with all possible upgrades is around ~100 (new roof, triple-glazed windows, hollow wall filled with insulation, new heating system, etc.).
from about 150 on, houses have significant insulation needs. at 250 the house is basically uninsulated, at 400 even the most basic things are missing (basically like windows tilted open).

these are just rough approximations. you also have to look at how the value was calculated. if you buy a house with 250, a lot needs to be done. houses under 100 are top renovated or new.

the unit is by the way khw/(m²*a) (a=year)

Look up efficiency classes Envkv. There are the categories. It is always spoken of kWh heat loss per sqm of living space. 300 kWh/sqm for a 120 sqm old building would mean 36000 kWh heat... with gas correspondingly 2500€ per year. If the house had 240 sqm it would be 5000 €. As far as I know (please check) there is also the difference between demand and consumption. Demand is difficult because it changes with user behavior: keyword grandma in the warm living room.

I don't have the value for kfw55 (good "standard new building") at hand right now, but it should be around 50-60.)

According to Wikipedia, the value for a KFW 55 is below 35 kWh/(m²·a)

The calculated value. In reality, it then depends on whether this is rather optimistically calculated or not (e.g. with solar heating support...).

depending on whether you take heating energy demand or primary energy demand :) the primary energy demand is "the main result of the energy demand calculation according to guideline... " (wikipedia).

the difference between demand/consumption lies in the age of the house, or rather the last major insulation. I think it was built in 79 or so?! if it's older you have to create a demand certificate, before that you can also choose consumption. (or was it exactly the other way around? it just doesn't make sense)
the energy certificate "consumption" is worthless because you don't know the heating behavior.