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Posted by: Breath on the Wind on 2009-11-08, 11:05:26
The efficiency of almost every electric heater is very good. They take the electric energy and turn it into heat. However this is not a measure of economics as in many places electric energy is costly for resistance heating. A heat pump is far more economical but the initial cost is higher. Economics would take into consideration alternatives and the general situation. The attic or top floor of a house is the one with the most exterior surface area (to loose heat to the outside) and the most distance from the furnace (so the furnace is pushing the least heat here.) As such it will tend to be colder unless there is another heating plant in the attic pushing down. Additionally if the walls are poorly insulated the top floor will take all of the heat from the rest of the house as it rises and pass it along to the outside. Last the greater the difference between an object and its surroundings the greater will be the heat loss by radiation, conduction and convection. This is where heater design makes a difference. Almost all heaters will cycle on and off. A more economical heater will be on for less time and make you feel warmer. If you are trying to heat a space to around 70 deg and you do so by heating the space to 75 nd then letting it cool to 68 before you restart the process you will have more heat loss than if you kept it at 70. The normal resistance heater is something like this. The oil filled heaters tend to even out the cycling a bit. They may have longer on times but will also have longer off times. The best option is an electric radiant heater that you point at people only while they are present. It is intended to transfer heat more by radiant energy (the part of light that transfers heat energy) than by conduction or convection. The room can still be 60 deg but you feel comfortable while in the line of sight of the heater. The on time is only when people are present and the off time is when they are not. |
