Short version? For a single tent up to 150cm, get the AC Infinity Hydrone 5 (£149.00) and plug it into a controller. Bigger tent, or a few plants in a spare room? The AC Infinity Hydrone 7 has its own humidity and VPD sensor built in. Watching the pennies, the RAM 20L at £173.00 sets a target humidity and just gets on with it. And if you're running a proper room with a lot of light in it, that's Quest 70 or Alorair Sentinel HD55 territory. Doing a winter tent from scratch? The AC Infinity Cold Weather bundle puts a Hydrone 5 with a heater and humidifier and saves you £30.01.
The best dehumidifiers for grow rooms
AC Infinity Hydrone 5
Built for grow tents rather than damp bedrooms, which is half the point. Covers a tent up to 150 x 150cm, roughly six plants, and it's small enough to sit in the corner without taking a plant's spot.
- Tents up to 150 x 150cm
- 10 drying levels
- Down to 25% RH
- Dual 6" duct ports
- UIS port
- PWM rotary motor ramps up and down in ten steps instead of slamming on and off
- Made to keep working in cold rooms too, so a chilly garage tent in winter isn't a problem
- Two 6" ports, so you can duct the dry air straight into the tent or run it closed loop with a bit of 6" combi ducting (£10.00 for 5m)
- Gravity drain hose option, so you're not stuck emptying a 2 litre tank
AC Infinity Hydrone 7
The big brother. Rated for spaces up to 10 x 10ft, around 12 plants, and unlike the Hydrone 5 it has its own humidity and VPD controller with a corded sensor. Plug it in, set a number, done.
- Up to 10 x 10ft
- On-board humidity and VPD control
- 8L real-world draw rate
- 235 to 610W
- The sensor's on a lead, so it reads the canopy and not the hot air coming off the back of the unit
- Hook it to an AC Infinity smart controller and you get the app, data charts and alerts
- Same dual 6" ports and drain hose option as the Hydrone 5
RAM 20L Dehumidifier
No app, no fuss. Set a target humidity between 30% and 80% and it only kicks in when the room goes above it. Pulls up to 20 litres a day.
- Up to 20L a day
- Target 30 to 80% RH
- 4.3L tank
- Continuous drain
- Quiet mode
- Tank full? It sounds an alarm and switches itself off rather than flooding the floor
- Run a hose to a bucket or a drain and you can forget about the tank altogether
- Quiet mode dims the display and drops to the lowest fan speed, handy for overnight
Ora Dehumidifier 60L
When the RAM can't keep up but Quest money isn't happening. Up to 60 litres a day, a 6 litre tank and the option to run to waste.
- Up to 60L a day
- 6L tank
- Run to waste
- Dual speed fans
- 650W
- Runs continuously or stops once it hits your target RH
- Built-in timer and sleep mode
- Handles and castor wheels, because nobody wants to carry this one
Alorair Sentinel HD55
Built for crawlspaces and cellars, which tells you how little room it needs. 32 litres a day at 26°C and 60% RH, and you control it from a separate remote unit on a Cat 5 cable.
- 32L a day (AHAM)
- Remote controller
- Gravity drain
- Under 50dBA
- Works 1 to 40°C
- Both the unit and the remote have a humidistat, so you can park the machine outside the room and duct the dry air in
- Auto defrost and a low temperature rating, so cold rooms don't faze it
- 1 year parts and 5 year compressor warranty
Quest 70 Overhead Dehumidifier
Designed in the USA for indoor growing, and rated at grow room conditions rather than a hot, soggy lab. 26 litres a day at 26.7°C and 60% RH. Sounds lower than the Ora's 60 litres. Different test conditions though, so don't compare them straight.
- 26L a day at 26.7°C / 60% RH
- 2.2 litres per kWh
- MERV-13 filtration
- Plug and play
- Hang it out of the way with the Quest 70 hanging kit (£109.90) and get floor space back
- Add the Quest 70 duct kit (£60.00) for awkward rooms
- Keeps controlling humidity whatever the temperature outside is doing
Shop all grow room dehumidifiers
Those litres-per-day numbers
This catches loads of people out.
Most dehumidifiers are rated at about 30 to 32°C and 80% humidity. Hot and wet, so the machine pulls loads of water and the box gets a big number on it. Your grow room isn't like that. Quest reckon a unit claiming 50 litres at those conditions pulls about 60% of that in a grow room.
You can see it on the Alorair. 60 litres a day at 30°C and 80% RH, 32 litres at 26°C and 60%. Same machine. The Quest 70 is only ever quoted at grow room conditions, which is why its 26 litres isn't as small as it looks.
So how much do you need? Every litre your plants drink comes back out of the leaves as water vapour. In a sealed room with no extraction it all has to go somewhere. Quest's rule of thumb is about 10 litres a day of dehumidifying for every 1000W of light, and to go bigger if you're not sure. Rather that than a mouldy crop in week seven.
At a glance
| Dehumidifier | Best for | Rated removal | Price |
|---|---|---|---|
 AC Infinity Hydrone 5 |
Tents up to 150cm | 4L real-world draw | £149.00 |
 AC Infinity Hydrone 7 |
Up to 10 x 10ft | 8L real-world draw | £269.00 |
 RAM 20L |
Rooms over 4m² | Up to 20L a day | £173.00 |
 Ora 60L |
Bigger rooms on a budget | Up to 60L a day | £518.00 |
 Alorair Sentinel HD55 |
Tight spaces, ducted installs | 32L a day at 26°C / 60% | £980.00 |
 Quest 70 |
Sealed commercial rooms | 26L a day at 26.7°C / 60% | £1,249.94 |
Prices as at October 2026. Check the product page for the live price. Removal figures are as each brand rates them, so they don't line up exactly.
How to choose
- One tent, up to 150cm? Hydrone 5 plus a controller. If you'd rather have an app and a VPD probe in the box, the VIVOSUN AeroDrain D12 (£269.99) covers the same size tent at 12 litres a day.
- Big tent or a small room? Hydrone 7, or the RAM 20L if the budget's tight and it can sit outside the tent.
- Extracting all the time? Your fan is already taking a lot of moisture out. You might only need a dehumidifier for lights-off and late flower, so start small.
- Sealed room, no extraction? Size it on the 10 litres per 1000W rule and go up a size. Quest 70 or the Alorair.
- No drain nearby? Get a unit with a decent tank, or add a condensate pump like the Little Giant VCC-20S (£90.00).
Getting heat under control at the same time? Our guide to cooling a grow tent goes through it, and the extraction guide covers sizing a fan.
Quick answers
Do I need a dehumidifier in my grow tent?
Not always. If your extraction keeps humidity where you want it, you might be fine. But if it climbs at lights-off or in late flower, or the tent's in a cold, damp space, a dehumidifier is what stops mould and bud rot.
What humidity should a grow tent be?
It changes with the stage. Higher for seedlings and cuttings, lower as you get into flower, and lowest towards the end. Units like the AC Infinity Hydrone 7 and VIVOSUN AeroDrain D12 can work off VPD instead, which takes temperature into account too.
What size dehumidifier do I need for my grow room?
For a sealed room, Quest suggest roughly 10 litres a day for every 1000W of light, and going bigger if you're unsure. Check what conditions the rating is quoted at, because most domestic ratings are at 30 to 32°C and 80% humidity.
Should the dehumidifier go inside or outside the tent?
Tent units like the AC Infinity Hydrone 5 and Hydrone 7 go inside or duct dry air in through their 6 inch ports. Room units like the RAM 20L need space around them, so they usually sit in the room outside the tent.
How do I stop emptying the dehumidifier tank?
Run a drain hose to a bucket or a drain. Most units here have a drain or run to waste option. If the drain is higher than the unit, add a condensate pump.
Still stuck? Give us a ring on 020 8686 9643 or email info@thehydrobros.com.
Or pop into the shop for a natter: Unit 12, Progress Business Park, Progress Way, Croydon CR0 4XD.
More grow guides
- Best clip and circulation fans
- Best carbon filters for grow tents
- Best grow tents by size
- How to cool down a grow tent
- Grow room extraction: choosing a fan and filter
- Grow tent setup guide
The Hydro Bros Team. We sell this kit and talk growers through it every day in our Croydon shop.
