Linearly controlled heating elements are electric heat generators which output can be adjusted from 0 to 100%. They are not switched off and on by a thermostat as it is the case with conventional thermostats. This linear power function is essential for operation with photovoltaic electricity because the available power is constantly changing due to irradiation and other consumers in the house. Pay attention to the technology: Only so-called "high-frequency clocked" converters do not cause mains disturbances and can be connected without any problems.