In most cases a warm cord does not mean that there is a problem with a heater. The most common causes for that are: An old or worn out outlet: If there is a loose connection between the plug and the socket then that will cause resistance and in turn heat build up. If there is not a tight fit between the plug and the outlet then the outlet should be replaced by qualified personnel. An overloaded circuit: Heaters can use up to 1500 watts of electricity and if you have other appliances in either the same outlet or on the same circuit breaker then a warm plug or tripping of a circuit breaker can occur. Under rated wiring: In some older homes the wiring is unable to support the amount of wattage used by the heater, which can be as high as 1500 Watts. Under rated Extension cord: An underrated extension cord causes resistance and heat builds up. You must use at least a 14-gauge extension cord rated for at least 1875 watts if an extension cord must be used.