You waste energy and money if you turn it on to heat a room but then leave it unoccupied.
You must make use of a current, efficient model.
You can experiment by changing the temperature on your thermostat to observe how it affects energy use and your sense of comfort.
You will need to run the space heater all day if your house is not well-insulated, increasing costs.
Electric space heaters generate one unit of heat for every unit of power, which means the heaters are 100% energy-efficient.