Why infrared sauna consumes less electricity

In a recent comparison of infrared heaters with electrical stove I showed that infrared sauna consumes 4-5 times less electricity than conventional sauna. In this post I will explain why it is so and how it follows from the basic physical principles.

There are three ways heat can transfer from its source (heater) to surroundings (sauna). These ways are convection, conduction and radiation.

Convection works through movement of matter. In a sauna the matter is the air that becomes warm near the heater and then moves to other parts of the sauna rooms.

Conduction is the transfer of energy from particle to particle. Nice example of these is a spoon that turns hot when put into a hot cup with tea or coffee. Different materials conduct heat differently. Metals are good for conducting heat, while air is not a good heat conductor.

Radiation is a transmission of energy with electromagnetic waves. It can pass through transparent (for a certain wavelength) media from the source to the destination without losing its energy. For example, radiation is the way how sun heats the earth. All that rays that left the sun and hit our earth carry all energy they have through all the space. They become absorbed by the earth thus heating our planet.

The ways by which conventional and infrared heaters transfer heat are different. Conventional heater heats sauna room mainly by convection. From these follows that a traditional sauna should have higher temperature to make us sweat – as we receive heat mainly from the air that surrounds us (however there is a portion of infrared rays, as all hot surfaces generate infrared).

Infrared heater, while being hot too, transfers a lot of heat via infrared radiation, which means our bodies receive it directly from heaters, and less energy is wasted to heat the surrounding air. That’s why to get equivalent sweating infrared saunas can be heated to lesser temperatures than conventional saunas.

So, the conventional sauna stove consumes more electricity because it should heat the air to higher temperature and sustain it for a sauna session, while infrared heater is more energy efficient because it transmits heat through infrared rays to a human body directly. Because of that the temperature in an infrared sauna can be lower to make us sweat and amount of electricity consumed is times less.

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