There's a debate these days related to the australian ban of traditional light bulbs, because of the loss of heat energy: http://www.ens-newswire.com/ens/feb2007/2007-02-21-01.asp But in a colder place than Australia (like Norway), it think this number would be lower than 66% because some of the heat from the light bulbs will just compansate the output from the thermostat convection heater . But do for instance 1000W of traditional light bulbs (or about 17 60W light bulbs...) heat the air in a room to the same temperature as a 1000W convection heater? Wikipedia says this about radiative heaters: and convection heaters: Do light bulbs heat a room in the same manner as radiative heaters, like "The element emits infrared radiation that travels through air or space until it hits an absorbing surface, where it is partially converted to heat and partially reflected"? Or do light bulbs heat the air directly as convection heaters? If light bulbs are more like radiative heaters, would they heat the room with less energy efficiency than convection heaters, because more of the heat energy would be transfered directly into, for instance, the walls and the roof where the heat loss is greater (when it is colder outside than inside)? About 95% of the energy input to traditional light bulbs produce heat. Some people wants to keep the traditional light bulb because of its alleged comfort advantage.