It’s very hot at the moment, so realistically speaking, dehumidifiers probably aren’t on your mind right now. The thing is, even though most of our focus is going to understandably rest on trying to stay cool, summer humidity does the same damage as winter damp…it’s just easier to ignore.
Steamy showers, back-to-back laundry loads and muggy, still summer air all push moisture levels up in exactly the same way it does in winter months – leading to mould problems later on. It’s probably the last thing on your mind at the moment, but sorting a dehumidifier out now means you can step into autumn ahead of the problem, rather than scrambling to fix it once the condensation starts to form.
Luckily, we’ve put together a helpful guide – everything you need, step by step – for making the right choice for your home.
Why damp happens
This might seem like an odd starting point, but understanding why damp occurs can, in some ways, help you to stop it from taking hold of your home in the first place.
Damp is, at its core, a moisture problem. High humidity (too much moisture in the air combined with poor ventilation) leads to condensation which, if left unchecked, can lead to black mould. That’s bad news for your walls, your furniture, and – most importantly – your health.
Everyday life keeps humidity and moisture topped up all year round: showering, cooking, ironing, drying clothes indoors – all of these create the perfect set of conditions for moisture to build.
Dehumidifiers can aid in regulating the moisture content of the air in your home, but before you make any large purchases, you’ll first want to rule out an actual leak somewhere in your home.
A damp meter can tell you if a wall is holding excess moisture; if it is, and there’s no obvious cause like condensation, it’s worth getting a professional to trace the source. There’s no dehumidifier in existence that will fix a leaky pipe.
Do you actually need a dehumidifier?
In general, you’ll want to keep an eye out, at all times, for a few key indicators of moisture build-up. These include:
- Condensation on windows, even on a warm day
- Mildew spots on walls (different from mould – mildew scrubs off, mould is far more stubborn)
- A musty smell that lingers in certain rooms
- Watermarks in the basement
- Rotting wood or peeling wallpaper
- Laundry that won’t dry
Basements, bathrooms, kitchens and attics are the usual hotspots, but signs of moisture aren’t necessarily proof of an issue – grab a digital humidity reader and check the numbers. Ranges of 30–50% humidity in summer and 30–40% in winter are fairly normal, but if the number sits above 50%, this is where mould starts to become a real risk.
Opening windows or using extractor fans when cooking or showering is a low-effort lifestyle change that can help, as is putting lids on pans while boiling food. Depending on your living circumstances, you may find it beneficial to dry clothes outside, rather than on an indoor rack (though if you’re in an apartment block or have no garden access, this may not be an option.
Sadly, you may also need to consider removing or reducing the number of houseplants in your home. As pretty as they are, they also release water vapour into the air, so if you’re cultivating a small forest in your lounge…you may have to make some sacrifices. Sorry!
Depending on how appliance-savvy you are, it may be worth checking if your washing machine or tumble dryer is leaking or venting badly (or asking a professional to do it for you). Again, fixing an issue here may prevent a larger problem later down the line.
More easy DIY fixes for moisture include opening windows in the morning to release overnight moisture, and sealing any obvious gaps and cracks in walls with caulk.
These are the basics that can largely be tackled yourself, but if you’ve taken these steps and are finding this humidity is still creeping up – or the problem is bigger than a bit of extra ventilation can solve – a dehumidifier is genuinely the sensible next step.
How does a dehumidifier work?
There are three main types of dehumidifier, and they all work quite differently, so it’s good to know which one suits your circumstances.
Peltier (thermo-electric): pulls air over a cold heat sink using an electric current. Moisture condenses on the cold surface and drips into a water tank; dry air is released back into the room.
Compressor (refrigerant): works like a mini fridge. A fan draws air across very cold coils, cooled by a built-in compressor. Water condenses on the coils, drips into the tank, and the air is reheated and pushed back out warmer and drier.
Desiccant: uses a chemical desiccant on a slowly rotating wheel to physically absorb moisture from the air. Part of the wheel is heated so the collected moisture drips into the tank, and the dried air is pumped back into the room.
What size do you need?
In this context, “size” refers more to how many litres of moisture a dehumidifier removes per day, rather than its physical dimensions.
Domestic models range from around 250ml up to 20+ litres a day, and the right size unit will depend on the size of the space, how damp it currently is, and the room’s temperature.
The below table offers a guide based on the room size and severity of damp conditions.
| Room size | Mild damp | Moderate damp | Severe damp | Drenched |
| ~150 sq ft | 250ml/day | 500ml/day | 7L/day | 8L/day |
| ~300 sq ft | 1L/day | 8L/day | 12L/day | 14L/day |
| ~500 sq ft | 10L/day | 12L/day | 14L/day | 16L/day |
| ~1000 sq ft | 14L/day | 18L/day | 20L/day | 25L/day |
As a general rule, it’s better to buy the largest capacity you can reasonably afford, rather than settling for the smallest and cheapest option. Spending a little more for the overefficiency of a larger model just means it’ll work less hard, last longer, and cope better if summer humidity turns out worse than expected.
Pros and cons
As with everything, dehumidifiers come with their pros and cons.
Compressor (refrigerant) models remove around 10–25L of moisture a day, but they need a room temperature of 15–30°C to work well – which makes summer their strongest season. Typically, they’re widely available, come with high capacity, and are the most energy-efficient option above 15°C. On the downside, they can be louder than other types, and as we’ve established, they won’t work as effectively in temperatures below 15°C. This makes them best for a warm, humid living space during the summer months. Running costs are about £0.48/day, roughly £3.36/week.
Desiccant models typically remove around 7–12L a day, and work at lower temperatures where a compressor would struggle. They’re also quieter, lighter and easier to move around if needed. The caveat is that they’re a little less energy-efficient, and you may find that performance drops in warm rooms. They are well suited to garages, conservatories, or basements – more of an autumn/winter pick. Price-wise, you’re looking at about £1.20/day, roughly £8.40/week
Peltier (thermo-electric) models remove around 0.5–1.5L a day, and are specifically designed for small spaces. They’re very cheap to run, quiet, low maintenance and extremely portable. The tradeoff of this portability is that they’re not suited for large or very humid rooms and, like compressor models, tend to be weak in rooms below 15°C. That said, they’re a great solution for a single bedroom or small bathroom with mild condensation. In terms of cost, you can expect to pay around £0.04/day, or as little as £5 a year.
Key features to look out for
Some key features to keep an eye out for include:
- Adjustable humidistat – set your target humidity and let it self-regulate
- Inbuilt hygrometer – detects humidity automatically
- Automatic shut-off – switches off once the target is hit or the tank is full
- Auto-reset – remembers your settings after a power cut
- Defrost mode – prevents freezing in cooler conditions
- Continuous drainage – skip emptying the tank
- Castor wheels and a handle – useful for anything over 8L that you’ll want to move between rooms
The best way to use it
If you’re drying out a room for the first time, expect to run your dehumidifier for longer stretches – anywhere from 8 to 24+ hours depending on how humid the space is. Once you’ve hit your target humidity, 2–4 hours a day is usually enough to maintain it, and a model with an adjustable humidistat will manage this for you automatically.
A few practical tips to help you get the most of out it include vacuuming the room first (to avoid clogging the vent with dust), keeping doors and windows closed while it’s running and making sure you give it ample space – at least six inches on all sides, and don’t push it against a wall.
Servicing, maintenance and warranties
Regular maintenance can keep a dehumidifier running efficiently for years, and the upkeep is mostly straightforward. Empty the tank after each use, and clean it with warm soapy water every couple of weeks. With compressor models, you’ll want to check the coils for dust or ice build-up. Desiccant models need the air filter cleaned every two weeks or so, while Peltier models just need the vents kept clear of dust with a soft brush
Most units come with a 12-month manufacturer warranty – keep the receipt and proof of purchase somewhere safe – just in case anything goes wrong.
A Few Last Words
Dehumidifiers can occasionally be subject to safety recalls due to overheating risks. If you’re buying second-hand – including anything picked up cheap for a summer clear-out project – it’s worth double-checking the model and serial number against manufacturer recall notices before you plug it in.
Summer might seem like the wrong season to think about a dehumidifier, but it’s actually when the most popular type – compressor models – perform at their best. Test your humidity, pick the right size and type for your space, and you’ll be glad you sorted it before autumn’s damp weather arrives.
Please note this is a sponsored post.
