Air Coolers: Arctic Air & Evapolar

A few weeks every summer it gets uncomfortably hot indoors (where I live). I have no aircondition in my home and I can not easily install one either.

There are devices called air coolers. I have two from Arctic Air and two from EvaPolar. Would I recommend them?

First, lets quickly discuss the concept of creating cooling in a warm room.

A FAN creates an air flow without cooling the air. As long as the air is significantly cooler than your body (37C) you will experience a cooling effect (perhaps even when the air is warmer – I have little experience). If the air is 25C it will tend to make your skin 25C. If a lot of air passes by your skin that effect will be significant, but if the air is completely still it is a much slower process.

An AIRCONDITION works like a refridgerator. It is a machine that takes in air of one temperature and outputs air in two different streams: one cooler and one warmer. The warmer stream must be removed, and the cooler stream is sent into the room (or refridgerator). This costs energy (which is heat), so the warm stream gets more warm than the cold stream gets cold. It is important to understand that a refridgerator (or aircondition) in a closed space heats that space. A refridgerator left open makes your room warmer. An AC that does not send (the) warm air out of your home makes your home warmer. Properly installed and at a high energy cost an AC can truly cool a room or a home.

An AIR COOLER turns water into water vapour. That comes at an energy cost, but that energy is drawn from the air, effectively making the air cooler. To speed up this process an Air Cooler has thin wet membranes (large water-air contact area) and a fan (so the air around the membranes is constantly warm and dry). In theory this is very smart. In practice the effect is limited (but real). Apart from the fan, and air cooler does nothing different from just hanging your wet laundry to let it dry.


An air cooler raises the humidity of the air. With my understanding of physics I would say that the energy content of the air is the same, but the temperature is lower and the humidity higher. The human body cools itself by sweating (evaporating liquid on the skin) and this process is more effective in dry air. So when considering (evaporating) air coolers I think it is important to understand that the higher humidity can make it feel warmer.

If you live in a dry place (relative humidity below 50%) you may find that the Air Cooler is good. Dry air is not nice for your skin, nose and throat. If the humidity is already very high (above 75%) the air cooler may be of no use whatsoever.

Typical Effect

It is hard to make exact and scientific experiments in your own home. Some days are warmer, sunnier, more windy or drier. I wish I could tell you that “on the week without air coolers the average temperature was 23C, and on the week with air coolers the average temperature was 21C”, but that would require large scale and controled tests.

However, a typical air cooler (Arctic, or EvaPolar) uses a few liters of water every day (so it needs to be refilled). They have different speeds, which produce different noise and different effect. On medium speed you could expect:

  • Air in: 24C, 60% humidity
  • Air out: 21C, 75% humidity (measured just in front of the machine)

If you use it as a fan – directing the cool air towards you – you feel much cooler than with no fan. If you leave it on 24×7 in a room, I would guess the effect is not insignificant, but it is nothing like an AC.

Arctic Air vs Evapolar

I first bought to Arctic Cooling units. Later I bought two Evapolar units (one evaCHILL and one evaLIGHT).

Evapolar units are more expensive. The build quality feels good, and the evaLIGHT also has thermometers for in/out air and a few other features.

What I can say is that Evapolar units are significantly more quiet. So whenever noise is a problem they give you more cooling (like when you sleep or don’t want a loud fan noise).

Evapolar indicates on their web page that they use some hightech membrane materials that gives advantages. My impression is that the Evapolar units have a stronger air flow and drink more water during a day (at similar power consumption ~5VA).

So even though an Evapolar costs 2-5x more than the (cheap) competition, if noise matters to you, I can imagine you can get 2-5x more cooling from it on a typical day.

Power Consumtion

All units I have run on USB 5V and use from 0.3A to a little more than 1A depending on speed. This means you CAN run them from a PowerBank, a computer, or most any USB charger.

My Arctic Air units came without power supplies. evaCHILL comes with a USB-C-connector (but it runs on 5V, not 20V as is standard for USB-C), I doubt the USB-C-standard allows this. So don’t connect your evaCHILL to a 20V laptop charger.

Replacing membranes

The aircooler has membranes that absorb water which is evaporated. Only the water evaporates and inpurities remain in the membranes. So you will need to replace the membranes (at some cost) eventually.

In my case these units will be in use only a few weeks per year so I expect them to last a few years without changing membranes. I also have access to very pure tap water.


If aircondition is not a possibility and humidity is reasonaby low, and Air Cooler is probably the best you can do. If you prefer a more silent unit go for quality (Evapolar) rather than the much cheaper alternatives.

If all you want is a cool experience at your workplace (desk) a fan might be good enough – and in that case it will be cheaper, more silent and requre less maintenance. However an air cooler will give you a slightly cooler air flow.

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