OMG this is hilarious. Autymn (sp?) is a complete moron. As an electrical engineer, I can tell you with 100% certainty that allelectric heaters are 100% efficient. And efficiency is the ratio of output to input (power out/power in, in the case of heat generating appliances the inherent efficiency is 100%. In gas appliances the efficiency can range UPTO about 95% for the newer 'ultra high efficiency furnaces' as long as combustion air is supplied from an unheated source [that is why you have 2 pipes going outside from the furnace- 1 for combustion air and 1 for combustion gasses to be vented]. No gas appliance is 100% efficient. ) Efficiency of heating units DOES NOT DEPEND ON ROOM CONSTRUCTION. The lack of ability of the room to contain the heat does not affect the output rating of the heater, thus the efficiency is not changed. (Input is ALWAYS the same no matter what). So autymn (sp?) why don't you do some research on a reliable source (wikipedia is not considered reliable because it can be altered by anyone without regard for their qualifications).