The specially designed heating rods have a power output of 0–3000 kW and cost between 100 and 500 euros.
The advantage of this solution is that the excess energy is directed into a buffer – not the available energy. This is exactly the effect Musketier criticizes: during the day, the underfloor heating can overheat, while at night it cools down too much. Additionally, the hot water preparation consumes more energy than is actually available. And it is purchased at a higher cost.
However, the regulation is simple: at night, circulation and hot water preparation are deactivated. From the moment the sun shines, the buffer is charged.
Some inverters, such as those from Deye, even use weather data from [weather.com] to optimize planning.
So far, however, this is only theory for me – I myself am not yet using this solution.