Physical basics of heating with electricity

There are various prejudices about electric heating: inefficient, expensive, not very effective. You can read about the physical basics of heating with electricity and how this can be used to derive the efficiency of power heating systems.

Principle of resistance heating

That you can heat with electricity at all, based on the law of electrical resistance. It is called after his discoverer also Ohm's law. Also, the physical unit used for the resistance of an electrical conductor is the ohm. 1? corresponds to 1 V / A (volts per ampere).

Operating principle of electrical resistance

Current flow is based on the movement of electrons. Each conductor opposes the movement of the electrons but a certain resistance. This means that some of the energy is no longer transported, but is converted into heat energy.

The resistance values ​​of individual substances are different. The cross section of the conductor also plays an important role. In addition, the temperature also has an influence on the height of the resistance of a conductor.

By appropriate design conductors are produced, which have a particularly high resistance. These can be the following components:

  • Heating conductor (a simple, high-resistance wire)
  • Heating coil (a coiled wire, which has a higher resistance)
  • heating tape
  • Heating jacket
  • heating tape
  • heater
  • or special resistance elements


The conversion of the applied current into heat is almost lossless. Electricity heaters are therefore quite efficient. The fact that electricity heaters would work inefficient is therefore by no means physically correct. However, you always have to consider the overall efficiency of power heating systems.

Other possibilities

storage heaters

Not every electric heater is a resistance heater. In addition to the direct heating, there are also storage heaters (such as the night storage heater). Memory losses can occur here, which must be taken into account physically and technically.

heat pump

The heat pump also uses electricity to generate heat. However, the active principle is more akin to a refrigerator: a medium (air, groundwater or the ground) is deprived of heat, just as the refrigerator does with the food it contains.

The heat is then released into the air or to a liquid. Ideally, for example, with carefully designed geothermal systems, the heat yield can be quite a multiple of the electrical energy used.

radiant heating

In radiant heating, such as infrared heating, electricity is also converted into heat energy. Here, however, not convection heat is generated, but heat radiation, similar to the warming radiation of the sun when it hits the earth.

The efficiency of radiant heating is enormously high - it is about 2.5 times that of a modern gas condensing boiler. From a technical point of view, radiant heating is one of the most advanced and future-oriented technologies for heating a room.

The only problem here is the LCA when heating with electricity. In order to assess the overall efficiency, the efficiency of generating electricity must also be taken into account; in addition, the generation of electricity certainly has some negative environmental effects.

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