A 1000w heater is not suitable for an 8sqm room as described on Scroutz. For an 8sqm room, you should get at least 1200w. However, the ADAX representative was excellent in providing information, even though I contacted them late.

With 4 electric heaters: 3 of 2000W and one of 1400W, I heat a 196 sqm (open-space type) house without using any other heating method at the moment, and maintaining a temperature of 22 degrees on the level (out of a total of 3 levels in the maisonette) where I spend most of the day, while the temperature in the other two levels does not drop below 20 degrees.
All this with an additional consumption of 250W per month for the months of October and November. With the provider I have chosen, heating costs me 17 euros per month for 196 sqm.
I am waiting to see the consumption for the winter months.
I was confident about my choice before buying them, it remains to be proven in practice.
The cost of acquisition is paid off in less than 2 years.
It is the best choice I could have made for heating!
I wonder about the options of air conditioning, which dry the atmosphere and only heat for as long as they are turned on, as well as oil radiators that only heat 1 sqm around them.
The quality of the heat is comparable to that of radiators, with the difference that the heat is produced with the push of a button and not after half an hour (depending on the boiler and the distance from the apartment).
It should be noted that I lower the temperature to 20 degrees in each room at night, except for the bedroom floor where I set it to 22 degrees.
Cheap, clean, and very economical solution, and it is no coincidence that it is used by Scandinavians who know cold weather well!