Do I need a dehumidifier in a grow tent?

Not always. Good exhaust removes much of the moisture plants release. A dehumidifier helps when the room air is already humid, when the canopy is dense, or when humidity climbs after lights-off. Run your setup for a few days and watch the humidity reading before buying one.

What size dehumidifier does a 4x4 tent need?

Brands size these by tent rather than by a standard formula. Vivosun recommends the 12 L/day AeroDrain D12 for tents up to 5x5, and AC Infinity rates the HYDRONE 7 for 4–6 plants. If the room around the tent is also humid, a larger unit outside the tent may work better.

Should the dehumidifier go inside or outside the tent?

A small unit such as the AeroDrain D12 is designed to sit in the tent. Every dehumidifier also gives off heat, so a larger unit is often better placed in the room, drying the air the tent's passive intake draws in.

Do I have to empty the tank?

Only if you don't use the drain. Mars Hydro's unit has a 2.1 L tank or a drain hose for continuous operation, Vivosun's D12 offers two drainage options and shuts off when the tank is full, and Spider Farmer includes a drain hose.

What happens after a power cut?

Mars Hydro says its unit keeps its mode, fan speed, target humidity, calibration and timers after a power interruption, and Vivosun says the D12 restarts after an outage. Check this before relying on any unit unattended.

Best Dehumidifier for a Grow Tent

By GrowRighteous Editorial Team (AI-assisted research) · Updated November 13, 2026 (first published November 13, 2026)

Best for	Product	Why	Link
Highest rated capacity	Mars Hydro 38 pint (18 L/day) dehumidifier	Compressor unit rated 18 L/day, drain hose or 2.1 L tank, RJ12 link to Mars Hydro's iControl system.	Check price
Best for a Spider Farmer setup	Spider Farmer 32 pint dehumidifier	App control and an RJ12 cable for Spider Farmer's GGS controllers, with a drain hose included.	Check price
Compact, inside-the-tent option	Vivosun AeroDrain D12	Up to 12 L/day, rated 42 dBA or less, recommended for tents up to 5x5, with two drainage options.	Check price
Best for an AC Infinity setup	AC Infinity HYDRONE 7	Built-in controller that adjusts drying output to hold a humidity or VPD target. AC Infinity rates it for 4–6 plants.	Check price

Plants release most of the water you give them back into the air. In a closed tent that moisture builds up, especially in late growth, when the canopy is dense, and at lights-off, when the tent cools. Mars Hydro notes that dense canopies trap humidity inside the tent during flowering, which is exactly when high humidity is most likely to cause problems.

A dehumidifier is the fix when exhaust alone can’t keep up. This guide compares four units made for grow tents from their published specs. We found no independent capacity or noise measurements for any of them.

Try ventilation first

Before buying a dehumidifier, make sure your exhaust is doing its job. An inline fan sized with a little headroom and a passive intake low on the opposite side (LONGWELL recommends 1 square foot per 400 CFM of exhaust) removes humid air continuously. Our inline fan guide covers sizing. If the room the tent pulls air from is itself humid, though, more exhaust just pulls in more humid air, and a dehumidifier becomes necessary.

What to compare

Rated capacity (pints or liters per day). Manufacturers measure this under their own test conditions, which are rarely the conditions in a tent. Use it to compare units, not to predict exact performance.
Drainage. A drain hose means you don’t empty a tank every day. Check that the hose outlet can sit lower than the unit.
Controller integration. An RJ12 or app link to your tent controller lets it work with the fan instead of against it.
Restart after power loss. Important for anything running unattended.
Heat. Dehumidifiers warm the air. Inside a tent, that adds to the light’s heat load.

The four units

	Mars Hydro 38 pint	Spider Farmer 32 pint	Vivosun AeroDrain D12	AC Infinity HYDRONE 7
Rated capacity	18 L/day (38 pints)	32 pints	Up to 12 L/day	Not stated on category page
Type	Compressor	Not stated in listing	Compressor	Not stated on category page
Tank / drain	2.1 L tank or drain hose	Drain hose included	2 L tank; two drainage options; auto-off when full	Not stated on category page
Control	RJ12 to Mars Hydro iControl; included temp & humidity sensor	App control; RJ12 cable	Built-in temperature, humidity and VPD sensors	Built-in AI humidity/VPD controller
Sized for	Up to 300 sq ft, depending on conditions	Not stated	Tents up to 5x5	4–6 plants
Rated noise	Not stated	Not stated	42 dBA or less	Not stated
Restarts after power loss	Yes, keeps settings	Not stated	Yes	Not stated

All figures are from each brand’s own listing, checked November 13, 2026.

Mars Hydro 38 pint (18 L/day)

The highest rated capacity here. Mars Hydro’s compressor unit connects to its iControl system over RJ12 for automated humidity and VPD control, keeps its operating mode, fan speed, target humidity, calibration and timers after a power interruption, and uses a 2.1 L tank or the included drain hose. Mars Hydro rates it for up to 300 square feet depending on conditions, so it is more unit than a single 4x4 needs; it makes most sense placed in the room around one or more tents.

Spider Farmer 32 pint

Spider Farmer’s unit is built to join its GGS smart-control system, with app control, an RJ12 cable and a drain hose. Its listing gave us few other specifications. Under Spider Farmer’s warranty policy, GGS series devices get 2 years and grow accessories 1 or 2 years depending on category; check which applies before you buy.

Vivosun AeroDrain D12

The D12 is the compact option meant for the tent itself. Vivosun lists a compressor rated up to 12 L/day, a 2 L tank with automatic shut-off when full, two drainage options, built-in temperature, humidity and VPD sensing, a rating of 42 dBA or less, an operating range of 35–85% relative humidity, and a recommendation for tents up to 5x5. It restarts after a power outage. Vivosun’s warranty policy gives most products 2 years.

AC Infinity HYDRONE 7

AC Infinity describes the HYDRONE 7 as having AI programming that adjusts drying output in exact percentages to hold a humidity or VPD target, and rates it for 4–6 plants. Its category page does not list capacity or tank size. AC Infinity covers its products for 2 years. It suits a tent already run by AC Infinity controllers; see Vivosun vs AC Infinity for how the ecosystems compare.

Placement tips

Inside the tent: use a compact unit, keep it off the floor if water could pool, and route the drain hose out through a low port.
Outside the tent: a larger unit drying the whole room lowers the humidity of the air your passive intake pulls in, and keeps its heat out of the tent.
Watch lights-off. Humidity usually rises when the light switches off and the tent cools. Our setup guide recommends a 24-hour dry run to see this before plants go in.

How these picks were made

We compared dehumidifiers that each major grow-tent brand sells for use with its own controllers, on published capacity, drainage, control integration and power-loss behavior. We did not test these units ourselves, and we found no published independent measurements to cite; see how we research.