What’s the best heater for a marijuana grow room?

So now the cold weather has set in and it looks like being a long winter, many marijuana growers are looking to add heat to their grow room.  Its not just us LED growers who need to think about warming up their areas, even a HID grow can get cold during the dark hours if its not part of a warmer environment. What is the best heater for a marijuana grow room?

Some quick facts first:

Cannabis likes to grow in the 21-29ºC temperature range. There is an argument for letting temps get hotter than this, particularly in mid-late flowering (not too much hotter though guys!). Below this range too, transpiration and photosynthesis will slow down, and once you get steady temps under 16ºc during lights on, you may as well give up all hopes of a bumper harvest. So once your environmentals fall to the early 20sC its time to start thinking about warming your grow room

I’m not talking about water temps (especially in hydroponic systems here, simply about ambient room temperature)

Firstly, if you don’t have one already, its REALLY worth investing in a min/max temp/rH thermometer. I don’t know what I’d do without mine, its as essential to my grow room as the pH/eC truncheon. Whenever there’s any kind of problem, I know it is not down to pH/ec/temperature/humidity as I’m keeping a constant eye on these all the time.

Indoor Humidity & Temperature Monitor: an essential piece of kit $10.69


Secondly think about what you need to heat. Assuming your plants are in a sealed area (such as a grow tent) you won’t want to put the heater in the room itself, but in the area outside, so that you are warming the intake air. I mention this because when I was looking at what type of heater to buy, I got distracted with the idea that I could double-purpose heating my cannabis grow room in the winter with providing breezes for the rest of the year (i.e. I was looking for a heater that would also work as an oscillating fan). Then I realised that for me (I use a Homebox GL tent) that wasn’t practical. My grow tent is packed with plants and I need to heat the air entering it not in it.


What’s the best way to keep the grow room warm?

  • If physically possible aim to heat the intake air rather than the grow area itself.
  • avoid fan heaters especially in the tent as these will scorch leaves

For those of you who want to heat a grow room though, I suggest you look at this heater: Lasko 755320 Ceramic Tower Heater with Digital Display and Remote Control.
The slimline tower design means that its space saving and the large digital display at the top mean you can easily see and set the room temps. It oscillates so that the heat is driven around the area rather than creating hot spots … and importantly it is described as being very quiet.

Useful features:

  • slimline design
  • digital display
  • thermostatically controlled
  • 8-hour timer


Best multi-purpose temperature & humidity control system

Whilst on the subject of distractions, I also came across this gem. Now I bought a portable air con unit last year which works fine during the hot summer months with my LED grow system (the LEDs don’t produce much heat but my ambient temperature outside the room hits & tops 100ºF). Now I’m looking at adding some extra warmth to the room, I wonder if it wouldn’t have been a better idea at the time to have bought one of these:


Best multipurpose temperature control

LX-140 WITH 14,000 BTU AC AND 14,200 BTU HEATER

Yes I know its pricey at $419.89 but when you think what even a portable air-con is going to cost you, this all in one heater / air conditioner / fan and dehumidifier will cover all year round climate control for your grow room. One thing that really makes it stand out is its big capacity dehumidifier (60 pints). It probably isn’t powerful enough to cool a large living space, but will work wonderfully to both heat and cool a grow room.

These double hose units help control smells as they circulate the same air over and over again using only the “outside” air as a source of cooling. Assuming you have a carbon filter on your exhaust fan, you can have a cool / warm room with no tell tale marijuana smells.

  • this recirculating air feature means you can easily use this unit with a CO2 unit maintaining temps and 1500ppm


  • Soleus LX-140 DB Portable AC All Season Comfort Control with 14,000 BTU Air Conditioner and 14,200 BTU Heater
  • 60 Pint Dehumidifier, Multi-color display, 3 speed fan with Oscillation, 24 Hour programmable timer, Programmable Thermostat & settings
  • Programmable LCD remote control, Dual Hose design, Energy efficient dual motor, Loss of power protection, Auto restart
  • Voltage: 115V (60Hz), Watts: Cool 1390W, Amps: Cool 12.5A, Watts: Heat 1180W, Amps: Heat 11A, Dehumidifier Capacity: 60 Pints/day, Air Flow: 225 CFM, Noise Level: 46 dB(A), Refrigerant: R-410A
  • Product Dimensions: 17.5 “W x 19″D x 32.75″H, Product Weight: 83 lbs.



Best heater for the grow room:

OK so that’s probably what I should have bought last year when I went for my portable air-con only single hose unit. But given that I’ve already got some form of heat removal for my grow room, I don’t need to double buy. Reading through a number of reviews and forum posts I realised that I (well the family) already owned the best heater for a marijuana grow room: an oil filled radiator.

Why does this heater work well in the grow room?

  1. Its economical
  2. It puts out a gentle heat all day (night) long. I use the thermostat controls and its just left on all the time.
  3. The heat radiates (DUH!!)  rather than is pushed out
  4. Completely silent
  5. Safe – automatic shut off if knocked over
  6. Comes on when temps drop too low and goes off when they get to my indicated “that’s warm enough level”
  7. Has a timer so I can preset to come on just before lights off
  8. We’ve been using it now for years .. in fact, now that I’ve requisitioned this one for the grow room, I have to replace it with a new one as our bedroom misses it!

DeLonghi TRD0715T Safeheat 1500W Portable Oil-Filled Radiator with Vertical Thermal Tunnels $76.00



You can also use these tubular heaters which fit nicely in a confined space:


read about why temperature is so important in the grow room

4 thoughts on “Best heater for a marijuana grow room

  1. the midnight toker says:

    i had the same heater campo . but now using tube bar heater with thermo stat . work just as good and much cheaper . well hear in the uk they are . i must say ive read most of your site n give great info on all aspects when growing indoors . i have recomended to some peeps here in the uk

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