Check that the space heater is plugged into a reliable power source and try plugging the heater into another electrical outlet. Extension plugs or faulty wiring can limit the electrical output flowing to the heater, thereby reducing its heat output.
Inspect the heater's electrical elements. Energy flows from the heater through the elements, which prompts them to glow and produce heat much like a stove-top element. One or more of these elements may burn out, reducing or stopping all heat output. Consult the heater's original manufacturer's user guide to determine how to obtain replacement elements.
Change the location of the portable electric heater if it seems to do a poor job of heating the room. A portable heater's small size means the heater performs best in enclosed areas that allow it to quickly heat up the surrounding air. Heaters setup near drafty windows, doors or vents may not perform at their best because they must constantly re-heat the air.
Clean the heater's vents. Dust, debris and other material can build-up on the vents, physically blocking the flow of heat from the heater's electrical elements. Use a soft cloth, brush or duster to dust the heater's vents away from the appliance so as not to push the debris into the eater.
Use a bigger heater if the portable heater fails to keep the room warm. While portable heaters have their advantages, they are also restricted by their physical limitations. Individuals trying to heat an entire house or large room may wish to consider a larger heating system.