Desiccant vs Compressor Dehumidifiers: Which Is Right for Your Application?

One of the questions I’m regularly asked is: “Should I use a desiccant or compressor dehumidifier?”

(Note: In commercial HVAC and moisture control, compressor and refrigerant dehumidifiers refer to the same core technology and are often used interchangeably.) 

It sounds like there should be a straightforward answer, but it really depends on the application. Both technologies have their place, and choosing the right one isn’t simply a case of looking at extraction rates or purchase price. 

The temperature of the space, the humidity level you need to achieve, the amount of moisture being generated and how the equipment will be used all play a part. 

In simple terms, refrigerant dehumidifiers are often a good choice for conventional humidity control at suitable temperatures, while desiccant technology can offer significant advantages where temperatures are low or very low humidity and specific dew points are required. However, the right solution always starts with understanding the application. 

How do they work?

At a basic level, both technologies do the same job: they remove moisture from the air. The way they do it, however, is quite different. 

Compressor (Refrigerant) dehumidifiers

A refrigerant dehumidifier draws moist air over a cold coil. As the air is cooled below its dew point, moisture condenses into water, which is then collected and drained away. The dry air is then returned to the space. 

It’s a well-established technology and can be an effective solution for many commercial and industrial applications. 

Our HiDew refrigerant range includes compact units for smaller applications, alongside industrial models designed for higher moisture loads and continuous operation. The HiDew SPR, STR, ID and IT ranges can also provide humidity and temperature control, with high-efficiency heat recovery options. 

Desiccant dehumidifiers

A desiccant dehumidifier works differently. Rather than condensing moisture, it uses a desiccant material to absorb water vapour directly from the air. The desiccant is then regenerated using heated air, allowing the process to continue. 

This approach can be particularly useful when operating temperatures are low or when very dry conditions and precise dew-point control are required. 

We supply Cotes desiccant dehumidifiers, including Modular, Mobile, Cold Store, Ultradry and Flexible systems. These cover a wide range of applications, from general industrial humidity control through to environments requiring very low humidity. 

So, which technology is better?

The honest answer is: neither is automatically better. 

In short, the rule of thumb that is best used is that if the conditions you require are below 15C or below 50% Relative humidity, then you should use a dessicant dehumidifier. If the conditions are both above 15C and 50% or above, then a refrigerant unit will work well in your area.

To expand, a refrigerant system can be an excellent choice where temperatures are suitable and conventional, or comfort humidity control is required. Our HiDew range, for example, is used across applications including commercial storage, museums, archives and other environments where effective moisture removal is required. 

As I have previously mentioned, compressor (refrigerant) dehumidifiers perform best in warm, ambient environments – typically above 15°C. As temperatures drop below 10°C–15°C, coils begin to frost over and extraction efficiency drops significantly. This is where desiccant technology excels, continuing to operate efficiently even in cold or sub-zero environments down to -20°C. 

The Cotes Cold Store range, for example, is designed for low-temperature and sub-zero environments, helping to control moisture and reduce problems such as condensation and ice formation. 

At the other end of the scale, Cotes Ultradry systems are designed for applications requiring exceptionally low humidity and precise dew-point control. 

So, as a general guide: 

• Refrigerant dehumidifiers are often well suited to conventional humidity control at suitable operating temperatures. If you’re above 15C and 50%, then refrigerant units are the way to go.

• Desiccant dehumidifiers can be particularly effective at low temperatures or where lower humidity or specific dew points are required. 

• The actual moisture load and operating conditions need to be considered before selecting the type and size of system. 

It’s not just about the size of the room

One of the things I would always advise against is selecting a dehumidifier based purely on the size of the space. 

Two rooms could be exactly the same size but have completely different dehumidification requirements. 

The first thing we need to understand is where the moisture is coming from. Are doors being opened regularly? Is there significant air infiltration? Is wet material being stored or processed? Is moisture being generated by a manufacturing process? 

Temperature and the target humidity are equally important. In more demanding applications, it can also be useful to consider dew point rather than relative humidity alone. 

All of these factors help establish the actual moisture load and, ultimately, determine what type and size of system is required. 

I should note that if the room is particularly small, there is an exception to the 15C and 50% rule. Sometimes in a space the dehumidification requirement is so low that any dehumidifier is oversized for a space. In this instance, you should always use a dessicant unit as the electric heaters used for regeneration are happy to switch on and off frequently. A compressor in a refrigerant system however, will wear very quickly if starting and stopping very frequently and then will eventually fail.

So, which should you choose?

As a general starting point, I would look towards a refrigerant dehumidifier where temperatures are suitable and conventional humidity control is required. I would consider desiccant technology where lower temperatures, very low humidity or a specific dew point are involved. 

But I wouldn’t make that decision without understanding the application first. There are plenty of situations where the answer isn’t immediately obvious, and that’s where technical advice can make a real difference. 

For me, good dehumidification starts with understanding the problem rather than simply selecting a machine. 

At Humidity Solutions, we provide both refrigerant and desiccant solutions, working with manufacturers including HiDew and Cotes. Our approach is to understand the environment, moisture load and required conditions before recommending a system. 

The aim isn’t simply to supply a dehumidifier. It’s to make sure the solution is suited to the application and will perform reliably in real-world conditions. 

Whether it’s a HiDew refrigerant system for a commercial storage environment or a Cotes desiccant system for a cold store or low-humidity industrial process, the right solution starts with understanding the conditions the equipment needs to operate in. 

If you’re unsure whether a desiccant or refrigerant dehumidifier is right for your application, I’d be happy to discuss your requirements. 

Freddie Kar 
Technical Sales Engineer, Humidity Solutions 

T: +44 (0) 1372 571 200 | M: +44 (0) 7766 258 680 | E: [email protected]