Grow Room HVAC: Why Air Conditioning Alone Won't Control Humidity, and How to Size Both Jobs
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Grow Room HVAC: Why Air Conditioning Alone Won't Control Humidity, and How to Size Both Jobs
Ask ten growers why their room is humid and nine will say the air conditioner isn't big enough. Sometimes that's true. More often the air conditioner is doing its job, which is removing heat, and nobody has given the room a machine whose job is removing water. Those are different loads, they have different equipment, and mixing them up is how people overspend on the wrong box.
ModernFarms sells both sides: Daikin 5-ton outdoor units for cooling and Anden dehumidifiers for moisture. This guide explains the difference between the two loads, converts a dehumidifier's pint rating into the same BTU/h units an air conditioner uses so you can compare them, and walks through an illustration for a sixteen-light room. Where we don't have a number we can stand behind, we say so.
The 30-Second Answer
Two jobs: an air conditioner removes heat (sensible load) and a dehumidifier removes water (latent load). A lit grow room produces both, and the water side is usually bigger than people expect. The conversion: one pint of water is about 1,090 BTU of latent heat, so an Anden 210 is about 9,500 BTU/h of moisture removal at its rating, a 320 is about 14,500, and a 710 is about 32,200. The example: sixteen 750-watt lights put out about 40,900 BTU/h of sensible heat, and depending on how moist the room runs, the latent side could call for anywhere from one 320 to roughly three. The takeaway: size the air conditioner for heat, size the dehumidifier for water, and don't expect either to do the other's job.
Sensible Heat and Latent Heat, in Plain Terms
Heat in a grow room comes in two forms. Sensible heat is the one a thermometer reads: the lights, the ballasts, the fans, and the sun on the building raise the air temperature. Latent heat is the energy stored in water vapor. When a plant transpires, it moves water from the root zone into the air, and that vapor carries energy with it. Removing the vapor, by condensing it on a cold coil, removes that energy.
The industry measure that ties the two together is the sensible heat ratio, or SHR: the sensible share of the total load. Trade coverage of cannabis facility design notes that standard HVAC equipment is built to perform best at an SHR of about 0.80 or higher, while grow rooms commonly run well below that, and in some cases below 0.50, meaning more than half the load is moisture. The same coverage observes that plants send roughly 70 percent of their irrigation water back into the air. Water in equals water out, and every gallon you feed the room has to leave through the dehumidifier or the drain.
Lighting sets the sensible side of the ledger. Nearly every watt a fixture draws becomes heat in the room, and one watt is about 3.412 BTU/h. Sixteen 750-watt fixtures, like our Gavita Pro RS 2400e, draw 12,000 watts and put out about 40,900 BTU/h, or 3.4 tons. Our Daikin cooling guide walks through that side of the math in detail.
Converting Pints Per Day to BTU/h
Air conditioners are rated in BTU/h or tons, and dehumidifiers are rated in pints per day. That makes them hard to compare, but the conversion is simple physics. Water has a latent heat of vaporization of roughly 1,050 BTU per pound, and a pint weighs about 1.04 pounds, so removing one pint takes about 1,090 BTU. Multiply by the pint rating and divide by 24 hours.
| Dehumidifier | Pints/day | Latent BTU/h (approx.) | Price | Price per pint |
|---|---|---|---|---|
| Anden A210V1 (240V) | 210 | 9,500 | $2,915.00 | $13.88 |
| Anden 320 V3 (277V) | 320 | 14,500 | $3,798.14 | $11.87 |
| Anden 710 | 710 | 32,200 | $8,857.20 | $12.47 |
Two caveats apply. First, pint ratings are measured at a manufacturer's test condition, and a dehumidifier removes less water when the air is cooler or drier than that condition, so a real room will see less than the rating on a given day. Second, a refrigerant dehumidifier puts its own heat back into the room as it works, and that heat becomes part of the sensible load your air conditioner has to remove. We don't publish a figure for that here because it depends on the model and installation.
The 320 is the better value per pint of the three, and the 277V version of it is in stock. The 240V version of the 320 is listed as out of stock at the moment, so check voltage against your service before you choose between them.
What Each Kind of Machine Costs per BTU/h
Here is where the two kinds of equipment look very different. Dividing price by capacity in thousands of BTU/h, the Daikin outdoor units come out between about $43 and $60 per 1,000 BTU/h of nominal capacity, while the Anden dehumidifiers come out between about $261 and $306 per 1,000 BTU/h of latent removal.
Don't read that as "dehumidifiers are overpriced." The comparison isn't fair in either direction. A Daikin's 60,000 BTU/h is a total capacity that combines temperature drop and some moisture removal, it covers only the outdoor unit, and it needs an indoor coil or air handler. Our Goodman 5-ton R32 air handler is $1,980.00, which changes the per-BTU math considerably. A dehumidifier, on the other hand, is a complete self-contained machine built to take water out of the air at a high rate even when the room is already cool. What the chart does tell you is that moisture removal is not a cheap by-product of cooling, and that money spent on the wrong half of the problem doesn't fix the other half.
A Sixteen-Light Illustration
Take that sixteen-fixture room. The lights alone are about 40,944 BTU/h of sensible heat. What the latent load adds depends on the SHR the room actually runs at, which depends on plant count, plant size, irrigation volume, and air exchange with the rest of the building. We can't know yours, so the table shows three illustrative cases using the relationship latent = sensible x (1 - SHR) / SHR.
| Room SHR | Latent load | Moisture to remove | Anden units that cover it | Dehumidifier cost |
|---|---|---|---|---|
| 0.80 | 10,236 BTU/h | about 225 pints/day | One 320 | $3,798.14 |
| 0.65 | 22,047 BTU/h | about 485 pints/day | Two 320s (or one 710) | $7,596.28 (or $8,857.20) |
| 0.50 | 40,944 BTU/h | about 900 pints/day | Three 320s | $11,394.42 |
The point of the table is the spread. The same lights, the same air conditioner, and the dehumidification bill ranges from about $3,800 to about $11,400 depending on how wet the room runs. That is why we won't hand you a one-size-fits-all rule of thumb. Dense canopies and heavy irrigation push a room toward the bottom of that range, and lighter loads push it toward the top. Pint ratings also fall short in real conditions, so treat the counts above as a floor.
The sensible half of this example needs about 3.4 tons from lighting alone, plus the heat from the dehumidifiers and everything else. One 5-ton outdoor unit starts at $2,585.00 for the 460V air conditioner, and the indoor side is extra. For the full cooling picture, use our dehumidifier and AC sizing calculator, and see our dehumidifier buyer's guide for form factor and brand comparisons.
Why Oversizing the Air Conditioner Doesn't Fix Humidity
The instinct when a room feels wet is to add tonnage. It usually backfires. Moisture comes out of the air when it passes over a cold coil for long enough to condense. An oversized air conditioner cools the room fast, satisfies the thermostat, and shuts off before it has run long enough to pull much water. The room ends up cool and clammy, and the cycle repeats. A dehumidifier controlled by a humidistat doesn't care what the temperature is. It runs when the humidity is high.
The same logic cuts the other way. A dehumidifier doesn't replace the air conditioner, because it doesn't lower the room's net heat. It adds a little. If your room runs hot in the afternoon with the lights on, add cooling. If it sits at the right temperature but the humidity won't drop to target, add dehumidification. Our VPD guide explains how temperature and humidity targets fit together, and our cooling guide covers smaller rooms.
Practical Setup Notes
A few things worth sorting out before the equipment arrives. Check the electrical first: the Anden listings are 240V or 277V in the versions above (check the voltage on each listing), the Daikin units are three-phase, and our electrical circuits guide explains how to count amps on a room. Plan the condensate path, since a dehumidifier produces a lot of water and the low-profile Anden condensate pump is listed at $107.33 if gravity drainage isn't an option. Think about air distribution, because the Anden duct kit for the A210V1 is listed at $519.63, and kits for the other models are listed separately. And plan the controls: the Anden digital dehumidifier control is listed at $137.37. A wall-mounted digital humidistat is listed too, but it shows as out of stock right now, so ask before you plan around it.
If this is a facility-scale build, cooling and dehumidification are usually two of the larger lines in the budget. ModernFarms finances projects over $25,000 for licensed facilities, and you can combine brands in one order. See our financing guide for what the program covers and what it doesn't publish.
Start the conversation
Send your room dimensions, fixture count, plant count, and electrical service to info@modernfarms.store or call 818-504-8165. We'll help you split the load between cooling and dehumidification before you order, and we'll tell you if you're asking for more than the room needs.
Frequently Asked Questions
Do I need both an air conditioner and a dehumidifier in a grow room?
In most lit rooms, yes. The air conditioner removes heat, which is the sensible load, and the dehumidifier removes water, which is the latent load. A standard air conditioner removes some moisture as a side effect, but grow rooms often carry more moisture than one can handle without overcooling the room.
How many BTU/h does a dehumidifier remove?
Water carries roughly 1,050 BTU of latent heat per pound, and a pint is about 1.04 pounds, so each pint is about 1,090 BTU. A 210-pint-per-day unit is therefore about 9,500 BTU/h of latent removal at its rating, a 320 is about 14,500, and a 710 is about 32,200.
What is sensible heat ratio and why does it matter?
Sensible heat ratio, or SHR, is the share of a room's total cooling load that is temperature rather than moisture. Standard air conditioning equipment is designed around a high ratio, and trade writing on cannabis facilities notes that grow rooms often sit well below it, which means moisture is a bigger part of the job than people expect.
Can one big air conditioner replace the dehumidifier?
Not reliably. An oversized unit cools the room quickly, shuts off, and removes little moisture in the short run time. A dehumidifier is built to remove water at its own pace regardless of whether the room needs cooling.
Does ModernFarms sell both?
Yes. We carry Anden dehumidifiers and Daikin 5-ton outdoor units, plus a Goodman 5-ton R32 air handler. We can help match them to your room before you order.
Can I finance an HVAC and dehumidification project?
Yes, as part of a project over $25,000 for a licensed facility. Rates, terms, credit requirements, and approval timing are not published, so ask for them in writing.
This article is general information, not engineering, electrical, financial, or legal advice. Latent and sensible loads depend on your room, plants, irrigation, and climate, and a licensed HVAC professional should size and install the system. The SHR cases above are illustrations, not measurements of your room. Prices, stock, and specifications reflect ModernFarms' live catalog as of October 6, 2026. We don't upsell, and we'd rather you buy the right machine for the right job.