Vendors of heat pumps and other space heater alternative soften engage in false advertising.


We've all seen ads proclaiming heat pumps as "more efficient than space heaters" this is simply not true. Heat pumps are more economical. A space heater operates at 100% efficiency, greater than that is impossible. In any system, the energy (heat) in must equal the energy out. A low resistance wire simply draw a large electrical current. Power == Voltage * Current. Since a wire does no other work, such as a motor would, all the energy is emmited in heat. Therefore, a heater drawing 5 amps on a 120 wall voltage line, is giving off 600 joules in heat per second (at 100% efficiency).

Heat pumps use the wonders of technology (I don't know about their inner workings) to transfer heat from an outside enviroment into your house. The operating power (the power it is drawing from the electric grid) is less than the heat gain, but the total energy in still equals the total energy out. The end result being heat pumps provide more heat per dollar than space heaters.
If a space heater is a wire which heats up, then it is not 100% efficient at producing heat. They also produce visible light, as you can easily see by looking at one. Even if all types of energy produced by a heater will eventually be converted to heat, if the energy like light energy converts to heat 1000 km away, then it's not going to warm you up. This can happen because of a new-fangled architectural invention called the window, which can allow light to escape.

Nothing is 100% efficient.

The simple way to understand this is that all the different types of energy that a space heater converts electricity into will eventually become heat:

  • The heating elements will transfer some of their heat energy to the atmosphere directly through convection.
  • Electromagnetic radiation given off by these elements because of their high temperature (both visible and infrared) will eventually be absorbed by some object in the room, increasing the object's temperature. This heat will be transfered to the atmosphere through convection as well.
  • Energy lost in the wires connecting the heater to the wall outlet is not really lost, it's converted into heat just as it is in the heating elements.
  • If the heater has a fan, this fan will accelerate the air around it, providing this air with kinetic energy. Eventually this kinetic energy will be lost through friction as the moving air collides with objects in the room. Friction results in this energy being converted into... Yup! Heat.

Space heaters, as well as any other appliance whose purpose is converting electricity into heat, do their job perfectly. It is a simple fact that most forms of energy will eventually become heat in the system. Entropy rises, that's life.

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