Electric heaters with a thermostat are designed to turn off when the desired temperature is reached and turn back on when the temperature falls below a certain level.
This can save energy compared to heaters that run continuously.
It's important to note that the energy efficiency of a heater also depends on factors like the size of the room, the insulation of the room, and the frequency of use.
Choosing an energy-efficient heater is just one step towards reducing your energy consumption and costs; it's also important to use the heater appropriately, such as by adjusting the thermostat, using it only when needed, and properly maintaining and cleaning the unit.