The Decision in 30 Seconds
Start with room temperature, then compare the actual models for extraction and electricity use at similar conditions.
If the target room is normally heated, shortlist suitable compressor models first, then compare their tested extraction, controls, noise and power use. Which? notes that refrigerant models are typically suited to normal room temperatures, while cold conditions can reduce their performance [S1].
If the space spends long periods cold — for example an unheated garage, caravan or outbuilding — include desiccant models in the shortlist. Do not buy from the technology label alone: confirm the model's stated operating range and performance information.
If your problem is condensation or mould inside a home, choosing a dehumidifier is only one part of the decision. UK government guidance says damp and mould can have multiple causes and the underlying cause should be identified and addressed [S2].
- Normally heated living space: compare compressor models first
- Cold or intermittently heated space: compare desiccant and low-temperature-capable compressor models
- Laundry: compare completed drying-session energy and drying outcome, not just rated watts
- Persistent local damp: investigate the source rather than simply increasing dehumidifier runtime
| Your situation | First shortlist | Verify before buying |
|---|---|---|
| Heated bedroom/living room | Compressor | Noise, extraction at realistic conditions, humidistat |
| Cold garage/outbuilding | Desiccant + suitable compressor models | Minimum operating temperature, low-temperature extraction |
| Indoor laundry | Either technology | Session kWh, drying result, laundry controls |
| Recurring mould/damp patch | Diagnosis first | Ventilation, leaks, cold surfaces, building defects |
Why Temperature Changes the Comparison
Compressor models condense water on a cold surface, while desiccant models capture moisture on an absorbent material.
A compressor dehumidifier cools incoming air so water vapour condenses, then returns drier air to the room. As room conditions become colder, the refrigeration system has less favourable conditions for condensation and may need defrost cycles. How much performance changes depends on the model [S1].
A desiccant model passes air through a moisture-absorbing rotor and uses heat to regenerate that material. This makes it a useful technology to compare for colder environments, although the regeneration process can mean higher electrical input.
The practical lesson is not 'below X degrees always buy desiccant'. It is to compare manufacturer or independent test data at a temperature and humidity reasonably close to the space you need to treat.
- Compressor: moisture is condensed using a refrigeration cycle
- Desiccant: moisture is captured by an absorbent rotor and released during regeneration
- Cold-room performance varies by model
- Auto-defrost can help a compressor operate in cooler conditions but does not make every model equally effective
| Question | Compressor | Desiccant |
|---|---|---|
| Moisture-removal method | Refrigeration/condensation | Adsorption + regeneration |
| Temperature sensitivity | Performance generally falls as conditions get colder | Useful technology to compare in colder spaces |
| Electrical input | Model-specific | Often higher because regeneration uses heat |
| Best evidence | Model data at relevant conditions | Model data at relevant conditions |
Do Not Compare Wattage Alone
The useful comparison is energy required to achieve the moisture-removal job.
A lower-wattage appliance is not automatically cheaper for a completed job if it has to run much longer. Likewise, a higher-wattage unit is not automatically more expensive if it reaches the required outcome substantially sooner.
For a home comparison, record the plug-in power or rated watts, the actual runtime, starting and finishing relative humidity, room temperature and — where possible — water collected. Session energy is calculated as watts divided by 1,000, multiplied by hours run.
Use the same electricity tariff for both options. Our running-cost calculator lets you enter your own wattage, runtime and tariff instead of relying on a price embedded in an article.
- Session kWh = watts ÷ 1,000 × runtime hours
- Session cost = session kWh × your electricity price per kWh
- Record starting and finishing RH and room temperature
- For laundry, compare the cost when the load reaches the same dryness outcome
| Metric | Why it matters |
|---|---|
| Watts | Shows instantaneous electrical demand |
| Runtime | Turns power into session energy |
| Room temperature | Helps explain performance differences |
| RH before/after | Shows whether the moisture-control goal was achieved |
| Water collected | Useful additional evidence, but affected by conditions |
Heated Rooms, Bedrooms and Living Spaces
For a normally heated living space, compressor models are usually the logical first group to compare.
Which? describes refrigerant dehumidifiers as typically best at normal room temperatures and notes that they can struggle in colder conditions [S1]. That makes compressor models a useful starting shortlist for many occupied UK rooms.
Do not assume all compressor models have the same extraction, sound or controls. Check independent tests or the manufacturer's data for the exact model, especially if bedroom noise or overnight operation matters.
If condensation keeps returning despite moisture removal, check ventilation and cold-surface conditions. Government guidance identifies inadequate ventilation, low internal surface temperature, heating issues and building defects among the factors that can contribute to damp and mould [S2].
- Compare exact model extraction rather than litres/day headline alone
- Check measured or specified noise if the unit will operate near sleeping areas
- Use a humidistat rather than arbitrary all-day runtime where appropriate
- Treat recurring condensation as a home-moisture problem, not just an appliance-selection problem
| Need | What to inspect |
|---|---|
| Bedroom use | Noise, lights, humidistat, tank-full shutoff |
| Living room | Extraction, airflow, placement, controls |
| Recurring window condensation | Humidity trend + ventilation + cold surfaces |
| Local mould patch | Underlying moisture/building cause |
Cold Garages, Caravans and Outbuildings
Cold-space buyers should make temperature performance a primary filter.
A garage or caravan can spend long periods at temperatures very different from an occupied living room. In that situation, headline extraction measured under warmer laboratory conditions can be a poor predictor of what you will see at home.
Check the minimum operating temperature, any low-temperature extraction data and how a compressor model handles defrost. Compare those results with an appropriate desiccant model rather than assuming either technology wins at every cold temperature [S1].
Also ask why the space is damp. Rain penetration, leaks or other building defects need repair; simply collecting water from the air does not remove the source [S2].
- Measure the room temperature over the times you expect the unit to operate
- Check the exact model's operating range
- Look for extraction data at lower temperatures where available
- Do not use a dehumidifier as a substitute for repairing water ingress
| Cold-space check | Decision use |
|---|---|
| Typical overnight temperature | Defines the conditions the appliance must handle |
| Minimum operating temperature | Rules out unsuitable models |
| Low-temperature extraction | More useful than warm-condition headline capacity |
| Defrost behaviour | Important for compressor performance in cooler air |
Laundry: Compare the Completed Drying Job
Both technologies can help with indoor laundry; compare them under the same load and room conditions.
Which? testing found that using a dehumidifier can materially speed indoor laundry drying in its controlled test, while also noting that results and running costs depend on the appliance and conditions [S3]. That supports testing the job rather than assigning one universal drying time.
For a useful home A/B test, use similar wash loads and the same spin setting, airer position and room. Record room temperature and RH, then stop each session at the same practical dryness outcome. Compare session kWh rather than cost per hour alone.
Keep normal ventilation needs in mind outside the focused dehumidification session. Government guidance identifies drying laundry as an indoor moisture source and stresses adequate ventilation as part of condensation control [S2].
- Use the same washing-machine spin setting
- Use comparable loads and the same room
- Record temperature, RH and session runtime
- Compare kWh at the same dryness outcome
| A/B test input | Keep consistent |
|---|---|
| Laundry load | Similar fabric weight/mix |
| Spin | Same washing-machine setting |
| Room | Same room and airer position |
| End point | Same practical dryness |
| Result | Runtime + kWh + RH change |
A Better Buying Checklist
Buy from measured room conditions and a defined moisture job.
Before choosing, measure the temperature and RH in the target room for several representative periods. Then define the job: controlling recurring condensation, drying laundry, managing a cold storage space, or temporarily reducing moisture while an underlying issue is fixed.
Shortlist models that can operate in those conditions. Compare extraction at relevant conditions, energy input, humidistat behaviour, noise, tank or drainage arrangement and manufacturer placement requirements.
If the home has persistent or substantial damp and mould, escalate the diagnosis. UK government guidance says the intervention should match the dwelling and underlying cause; simply removing mould is not enough if the moisture source remains [S2].
- 1. Measure room temperature and RH
- 2. Define the moisture-removal job
- 3. Shortlist models rated for those conditions
- 4. Compare extraction and session energy
- 5. Check controls, noise, drainage and placement
- 6. Investigate persistent damp or mould separately
| Before buying | Write down |
|---|---|
| Conditions | Typical room temperature and RH |
| Job | Condensation, laundry, cold space or temporary drying |
| Performance | Extraction at relevant conditions |
| Energy | Watts and estimated/observed session runtime |
| Usability | Noise, humidistat, drainage, placement |
Frequently asked questions
Is a desiccant dehumidifier always better below 15°C?
No. 15°C is a useful warning that temperature matters, not a universal switch point for every product. Compare the exact compressor model's operating range, defrost system and low-temperature extraction with the desiccant alternative [S1].
Which type is cheaper to run?
It depends on the model, conditions and runtime required to complete the job. Compare session kWh — watts divided by 1,000 multiplied by runtime hours — at a comparable outcome rather than comparing wattage alone.
Which type should I use in a cold garage?
Include desiccant models in your shortlist, but also check any compressor model specifically rated for the temperatures your garage reaches. The exact operating range and low-temperature extraction matter more than a generic technology rule [S1].
Which type is better for drying clothes?
Both can help. The useful comparison is how much energy each uses to bring a comparable load to the same dryness in the same room. Which? found a dehumidifier materially accelerated drying in its controlled test, but that result should not be turned into a universal time guarantee [S3].
Will changing dehumidifier type fix mould?
Not necessarily. A dehumidifier can reduce airborne moisture, but damp and mould can involve ventilation, cold surfaces, leaks or building defects. The underlying cause needs to be identified and addressed [S2].
Bottom line
Choose compressor versus desiccant from the room you actually have, not from a universal temperature slogan. Measure the target space, define the moisture job, compare exact-model performance at relevant conditions and calculate energy for the completed job. If damp or mould persists, investigate the underlying cause rather than treating a different dehumidifier as the whole solution.
Sources
Sources are shown so readers can check time-sensitive or factual claims directly.