I would say the most cost effective way of heating a home is to have north facing windows. If you want it to be warm when the sun isn't shining, the sun needs to to heat a thermal mass e.g. concrete floor. Finally, the stored heat can't be allowed to escape, i.e. insulation must be properly in place and there can't be any drafts. Cost to run this system is $0 and comfort level is very high. I love coming home to a house that is in the low twenties even in the middle of winter.
To answer the original question regarding heaters, 1 watt of electrical energy is turned into 1 watt of heat energy as pointed out by others. However, there are considerable differences in how effectively the heat is delivered to the recipient. A heat lamp under a desk or a heated foot pad may do the trick of coupling a greater proportion of the heat energy delivered by the heater into the recipient, allowing for a smaller appliance. Or possibly creating a cove to sit in and heating the cove by a radiator to capture more of the energy from the heater locally.
Radiant heat generally feels warmer than the same amount of convected heat (from a fan heater for example) because the convected heat is distributed by moving air, which also has a cooling effect. Raising the level of radiant energy bouncing around in a room is a more energy efficient way than raising the air temperature to heat people in the room - especially if there are drafts. Raising the radiant heat level is achieved by raising the temperature of surfaces, rather than the temperature of the air.
As well as the cooling effect of moving air, there is another effect at play. That is that there is a net transfer of energy by radiation from a warm body to a colder one, including from human bodies! So if we are in an environment of cold surfaces we will lose heat by radiation and tend to feel cold, even if the air is not particularly cold.
The energy efficiency of reverse cycle heat pumps is consistently overstated because of this. Rooms heated by air conditioning need to be at a higher air temperature than radiant heated rooms for the same comfort level, at least until the surface temperatures catch up to the air temperature which may take several hours.
Posted Sunday 13 May 2012 @ 3:58:04 am from IP
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