The therm-x2 radiator is setting new standards with the innovative, patented x2-technology. With serial flow through the radiator panels, in comparison to conventional radiators, it saves up to 11 % more energy, generates up to 100 % more comfortable radiant heat, and its heating period is up to 25 % shorter.
According to §559 German Civil Code (BGB), modernising with therm-x2 can be apportioned to rent.
You can read about the legal requirements here:
German Civil Code (BGB) §559 Rent increase after modernisation measures
Fewer complaints because of cold radiators can definitely save bother and costs.
30 min craftsman's work (60 € / hr.) + travel to and from the site
-> € 30 + € 30 = € 60 / complaint
Complaint in approx. 3 % of the housing stock
For example, 30000 apartments x 3 % = 900 complaints / year
-> 900 x € 60 = € 54000 savings / year