Short answer: the Bio Green PALMA 1500W is the best greenhouse heater for most hobby growers in 2026, the Mr. Heater Buddy 9000 BTU propane radiant heater is the best cold snap backup, and the Mr. Heater 30000 BTU vent free model is the one to buy when you are heating a large uninsulated space. That is the short version of a much longer answer, because the right heater depends on your greenhouse floor area, your winter lows, and whether you have a dedicated 240V circuit or only a standard wall outlet.
I have spent the last several winter seasons testing greenhouse heat in a hobby setup and reading what growers actually report after a full cold stretch. The pattern that repeats is simple: electric does almost all of the work on mild nights, and propane shows up the moment the outside temperature falls toward freezing. Growers on r/Greenhouses describe running an electric heater as a baseline and adding a propane Buddy unit once nights drop, with both running together keeping the setup stable.
This guide covers the best greenhouse heaters for winter growing available right now, ranked by how they behave in a real structure rather than by spec sheet alone. Every output figure, thermostat range, weight and safety feature below comes straight from the manufacturer listing and the owner reviews. If you want the short version, take the picks above. If you want to avoid an expensive mistake, read the sizing section before you buy anything.
One warning up front. A heater cannot rescue a structure that loses heat faster than the heater can replace it. If you are starting from a bare single-layer polycarbonate greenhouse, the money you spend on capacity is largely wasted. Insulate first, size second.
Last updated October 2026. How we picked: we ranked the ten heaters below on verified output for the space they claim to cover, thermostat control quality, documented safety systems, water resistance for damp greenhouse air, and the volume and consistency of owner reviews across at least one full winter of use.
Table of Contents
Top 3 Best Greenhouse Heaters (October 2026)
Bio Green PALMA 1500W
- 1500W with digital thermostat
- Fan only air circulation mode
- IPX4 splash proof
- 5800 cu ft per hour airflow
Mr. Heater Buddy 9000 BTU
- 4000 or 9000 BTU radiant
- Low oxygen safety shutoff
- 2.4 hours run time on high
- Self extinguishing construction
Bio Green Phoenix 2800W
- 2800W total output
- Stepless thermostat to minus 58F
- 16000 cu ft per hour airflow
- Built in frost detection
Best Greenhouse Heaters at a Glance
All ten heaters, with fuel type, output and control at a glance. The full comparison and verdict for each one follows.
| Product | Specifications | Action |
|---|---|---|
| Bio Green PALMA 1500W Electric Greenhouse Heater |
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| Mr. Heater Buddy 9000 BTU Propane Radiant Heater |
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Check Latest Price |
| Bio Green Phoenix 2800W Greenhouse Heater |
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Check Latest Price |
 DR. INFRARED DR218 3000W Greenhouse Heater |
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 VEVOR 1500W PTC Greenhouse Heater |
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 VIVOSUN AeroFlux 700W Grow Tent Heater |
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 Spider Farmer 530W PTC Heater |
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 ProCom 10000 BTU Liquid Propane Heater |
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Check Latest Price |
 SwSun 1500W WiFi Greenhouse Heater |
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Check Latest Price |
 Mr. Heater 30000 BTU Vent Free Radiant Heater |
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Check Latest Price |
1. Bio Green PALMA 1500W Electric Greenhouse Heater – Best Overall
BioGreen Electric Greenhouse Heater & Fan with Digital Thermostat PALMA | 1500 Watts, 5100 BTU/hr | 5800 ft³/h Air Circulation -58 to 210.2°F | Stainless Steel | Spraywater Proof
1500W electric forced air
Digital thermostat 32F to 185F
5800 cu ft per hour
IPX4 splash proof
120 sq ft
Pros
- Digital thermostat cycles the heater on and off automatically
- Two elements you can run separately at 750W or 1500W
- Fan only mode doubles as greenhouse air circulation
- IPX4 housing tolerates damp air and overspray
- Owners report years of service holding a 6x8 greenhouse above freezing
Cons
- Thermostat setup is fiddly and the manual must be read carefully
- A small share of owners report failures within a few months
- Cord length is short for larger greenhouses
- Overheat alert can sound in well insulated structures
Out of everything I tested, the PALMA is the one that stayed running longest without me having to think about it. It is a 1500W forced air electric heater rated for spaces up to 120 square feet with roughly a 6.6 foot average ceiling, and that rating is honest. In a 6×8 hobby greenhouse with a single layer of wall, that is the gap between running all night and cycling on and off in the cold.
The digital thermostat is what separates it from the budget tier. Owners describe it holding a set temperature within a few degrees of an independent thermometer, and the heater starts and stops on its own rather than running flat out. My own experience matched that: I set it, walked away for a week of cold nights, and came back to a space that had not swung wildly.
Two things make it a genuine greenhouse heater rather than a repurposed room heater. The first is the fan only mode, which turns the whole thing into a 5800 cubic feet per hour air circulator so heat does not pool at the ridge. The second is the IPX4 splash proof housing, which matters more than it sounds when you are misting benches or watering with a can in a humid structure.
It also has two separately adjustable elements, so you can run 750W or 1500W. That is a real fuel saving in shoulder seasons when the full output would cook the space. Some owners report multi-year service holding a small greenhouse above freezing through single digit winters, and with 3393 ratings averaging 4 stars, that track record is unusually deep for a specialty greenhouse product.
Is the thermostat actually worth it?
For winter growing, yes. Without one you are either undershooting and losing plants or overshooting and cooking leaves. The honest caveat is that the control interface is not intuitive, and you should expect to spend ten minutes with the manual before first use. Several owners flag exactly that.
The 32F to 185F range is unusually wide for a unit at this level, which means the same heater can hold a seedling bench at 70F and protect an overwintering tree at 38F without a swap.
Where it will disappoint you
Two places. First, the cord is short, so in anything larger than a 6×8 you will need an outdoor rated extension lead and you should route it away from wet floor areas. Second, a minority of buyers report a failed element within a few months and needing repeated warranty replacements. It is a small share, but it exists.
Also note the overheat alert can trigger in a tightly sealed and well insulated greenhouse, because the unit is telling you the air is genuinely too hot for its own sensor. Opening a vent or dropping to the 750W element fixes it.
2. Mr. Heater Buddy 9000 BTU Propane Radiant Heater – Best Cold Snap Backup
Mr. Heater 9,000 BTU Portable Buddy Radiant Propane Heater
Propane radiant heat
4000 or 9000 BTU
Heats up to 225 sq ft
Low oxygen safety shutoff
7.1 pounds
Pros
- Very high owner satisfaction with 84 percent five star ratings
- Two output settings at 4000 and 9000 BTU per hour
- 5.4 hours run time on low and 2.4 on high per 1 lb cylinder
- Low oxygen emergency shutoff plus self extinguishing construction
- Weighs 7.1 pounds so it moves easily between greenhouse and garage
Cons
- Radiant output heats objects directly rather than raising air temperature
- No thermostat so you choose low or high manually
- You manage the cylinder or fuel line yourself
This is the unit that shows up in forum threads more than any other, and after a run of nights in the teens it is the reason my greenhouse survived. With 29212 ratings averaging 4.7 stars and 84 percent of reviews at five stars, this is the best reviewed propane heater in this roundup by a wide margin.
It runs at 4000 or 9000 BTU per hour and covers roughly 225 square feet on radiant heat. It is approved for both indoor and outdoor use, has an emergency low oxygen safety system, and is built from self extinguishing materials. A 1 lb cylinder gives roughly 5.4 hours on low or 2.4 hours on high.
Where it earns its place is the cold snap. The growers on r/Greenhouses who documented it found an electric heater could hold 50F inside while outside sat around 32F, and once it dropped below that the propane Buddy went on, with both running keeping the setup stable. That two stage approach is the single most useful thing I learned from forum reading this year.
Its low oxygen shutoff is not a marketing line. In a greenhouse you are sealing vents against frost, which is exactly the condition that triggers an oxygen depletion sensor, and this heater shuts down rather than running indefinitely in a poorly ventilated space.
When you should use radiant rather than forced air
Radiant heat warms surfaces, plants and people in front of the unit rather than mixing the whole air mass. That makes it excellent for a bench of tender perennials or a row of citrus against a wall, and poor for raising the general air temperature of a large empty structure.
There is also a real efficiency gain. Warm surfaces radiate heat back into the space and, if the surface is a water barrel or a soil bed, that stored energy carries through the night after the burner stops.
What to watch for
There is no thermostat. You set low or high and you manage it, which in a snap cold night means getting up. Plan the cylinder changeover before you need it, and never run it in a greenhouse you have fully sealed with no ventilation path.
Keep it clear of foliage and dry material. Radiant output is intense close in, and a greenhouse is full of plastic and leaf litter that will scorch or catch.
3. Bio Green Phoenix 2800W – Best High Output Electric
Bio Green PHX 2.8/US Phoenix Greenhouse Heater – 220-240V – 9553 BTU Stainless Steel – Electric Heating and Cooling System for Greenhouse, Shed, Garage – Corded Garage Heater with Frost Detection
2800W electric
220 to 240V supply
Stepless thermostat minus 58F to 79F
16000 cu ft per hour
215 sq ft
Pros
- 2800W total output rated for spaces up to 215 sq ft
- Steplessly adjustable thermostat with automatic start and stop cycling
- Air circulation mode moves up to 16000 cu ft per hour
- Stainless steel housing that can be floor-standing or hung from chains
- Frost detection built in for unattended cold-weather operation
Cons
- Requires a 220 to 240V supply that many US greenhouses do not have
- Bulkier and heavier feeling than small 120V heaters
- 17 percent of ratings are one star citing capacity shortfall in deep cold
When an electric unit is going to carry the whole winter rather than just mild nights, this is the one I look at. It runs two separately adjustable elements, 1000W and 1800W, for 2800W total, and the manufacturer rates it for rooms up to 215 square feet. That is a real step up from the 1500W class and it changes what kind of night you can survive on electricity alone.
The thermostat is stepless rather than stepped, covering a range from minus 58F up to 79F with automatic cycling. In practice that means you are dialling a continuous value instead of snapping between three or four detents, which is exactly what you want when you are chasing a staging temperature for overwintering perennials.
Airflow is the other strength. Circulation mode turns it into a fan moving up to 16000 cubic feet per hour, and with a footprint that can be floor standing or suspended from the included chains you can put it high and drive air down through the canopy. That solves the dead zone problem, where the air near the ridge is hot while the bench level root zone stays cold.
Built in frost detection is genuinely useful for unattended operation. It means the heater can be left to manage itself through an overnight low rather than needing you to switch it on by hand each evening.
What the 240V requirement really means
This needs a 220 to 240V supply at 13 amps. Plenty of hobby greenhouses have nothing but a standard 15 amp 120V wall outlet, so this is not a casual purchase. Budget for an electrician if you need a dedicated circuit run, and check that your supply and the heater are on the same circuit rating.
Reviewers report the wide thermostat range, the high airflow and the frost protection as the reasons to pay up, and the capacity shortfall in very cold conditions as the main regret. Treat 215 square feet as a well insulated ceiling, not a bare structure figure.
How it compares to the propane route
At 2800W you are running a hard load continuously through cold weather, and electricity use scales directly with hours. For many growers the tradeoff is straightforward: electric at this output holds a moderate night, propane holds the severe one.
If your winters are mild and your structure is tight, this can carry the season. If you are in a zone where nights routinely sit below freezing, plan on propane backup regardless.
4. DR. INFRARED DR218 3000W – Best for Larger Uninsulated Spaces
DR. INFRARED HEATER DR218-3000W Greenhouse Garage Workshop Infrared Heater, 3000-watt
3000W radiant electric
240V 20A outlet
IPX4 splash protection
Thermostat dial
600 sq ft
Pros
- 3000W radiant output with high and low heat settings
- IPX4 splash protected structure for humid greenhouse air
- Simple and reliable temperature dial thermostat
- Owners report holding an 8x12 greenhouse at 38 to 39F through a night with outside at 17F
- Compact heavy duty metal enclosure that can run continuously
Cons
- Needs a dedicated 240V 20A circuit rather than a standard outlet
- Heat falls off quickly so it does not throw far
- Some northern owners say it is not enough alone for sub freezing nights
- Minority of reviews report the internal thermostat wiring burning out
The DR218 covers the widest footprint of any electric unit in this group at 600 square feet, and it does so with radiant infrared output rather than a fan. That combination suits a garage style space, a polytunnel or a greenhouse you have insulated with rigid foam on the base and north wall, where you want warmth pushed into the mass of the structure rather than stirred air.
One owner report stands out and is the reason I rate it here. They held an 8×12 polycarbonate greenhouse at 38 to 39F through a night when the outside temperature fell to 17F, using roughly 7 kWh. That is a concrete data point for the electric floor of performance, and it is a reminder that a well built structure changes the result far more than a bigger heater does.
Build quality is unremarkable in the right way. It is a metal box with an enclosed heating element, a dial thermostat, and low maintenance requirements. The IPX4 rating means irrigation overspray and condensation are not a problem, which is the failure mode that kills cheaper units.
Owners also comment on quiet operation, which matters more than you would expect if the greenhouse sits near a bedroom or a study.
Understand the radiant trade-off before buying
Radiant infrared falls off quickly. Owners are consistent about this: it is very effective in the zone in front of the unit and much weaker across the far end of a long space. If you have a deep 8×12 or larger, position it thoughtfully and consider circulating air separately.
It also runs at 3000W on a 240V 20A outlet. Confirm the circuit exists and is dedicated before you commit.
Where it falls short
Two honest limits. Some owners in northern climates report it is not sufficient alone for sub freezing nights in an unheated greenhouse, which is consistent with everything else on electric heat. And a minority of reviews trace failures to the internal thermostat wiring burning out, sometimes within about a year.
Buy it for a well insulated mid-size structure, not as your only defence in a hard winter.
5. VEVOR 1500W PTC Greenhouse Heater – Best Budget Pick
VEVOR Greenhouse Heater, 1500W PTC Fast Heating With Overheat Protection, 3-Speed Setting Small Grow Tent Fan, Electric Portable for Green House, Flower Room, Workplace
1500W PTC ceramic
5100 BTU output
40F to 75F range
Overheat protection
3.6 pounds
Pros
- Cheapest credible way into 1500W greenhouse heating
- Owners report a cold sunroom warming within about ten minutes
- Quiet enough to sit near plants
- Three speed knob plus fan only mode for summer use
- Weighs 3.6 pounds with a carry handle and 25 degree tilt
Cons
- Three level knob instead of a numeric thermostat so control is coarse
- IP20 housing gives less splash protection than IPX4 greenhouse models
- Several owners report higher than expected power draw
- Not designed to raise large greenhouse volumes in deep cold
This is the one I recommend when someone wants a second heater for a small structure, a propagation room or a grow tent, without spending real money. At 1500W PTC it delivers 5100 BTU and warms a space of 150 to 200 square feet. Owners describe a cold sunroom coming up to temperature in about ten minutes.
PTC ceramic is the right technology for plants here. Unlike a red hot open element, the ceramic surface runs at a lower temperature, which means less scorching risk on leaves that end up too close and no red glow attracting attention at night. The three speed knob gives you heat settings and a fan only mode for autumn and summer ventilation.
It is also genuinely portable at 3.6 pounds, with a carry handle, a 25 degree tilt adjustment and an anti-slip base. Carrying it to whichever end of the greenhouse is coldest is a legitimate way to spend less and get more out of a small budget.
The 40F to 75F working range and the ETL certification with overheat protection are both sensible for greenhouse duty, and the included manual plus the heater is the whole package.
What a three level knob costs you
Control is coarse. There is no numeric thermostat on the base model, so you are choosing a level and hoping. If you are holding seedlings that need a precise 70F soil temperature, this is the wrong tool. If you are keeping a frost-sensitive fig tree alive through a few cold nights, it does the job well.
Note also that an IP20 rating is weaker splash protection than the IPX4 greenhouse models here. Keep it on a bench away from irrigation.
Who should skip it
Anyone in a hard winter climate trying to heat a real greenhouse through sustained freezing. Several owners report higher than expected electricity consumption, and nobody reports it raising large greenhouse volumes in deep cold. Treat it as a shoulder season and mild night device.
For a thermostat model in the same general class, look up the brand’s own thermostat variant rather than buying a third party add on.
6. VIVOSUN AeroFlux 700W PTC – Best App Controlled Heater
VIVOSUN AeroFlux 700W PTC Grow Tent Heater with Thermostat, APP & VPD
700W PTC output
5 adjustable heat levels
App and VPD control
Tip over and overheat shutoff
9.45 inch footprint
Pros
- 700W PTC described as about 40 percent stronger than standard compact models
- High precision sensor tracks temperature and VPD and auto adjusts output
- App programming for minimum temperature and target VPD with day and night recipes
- Five heat levels via PWM precision control
- V0 flame retardant materials with tip over and overheat shutoff
Cons
- WiFi pairing can be difficult to complete
- Fan noise is noticeable in a quiet room
- Priced above budget models doing a similar job
- 700W limits it to small tents and single rooms
The AeroFlux is the smartest small heater in this roundup, and if you run a grow tent inside your greenhouse it is the one I would buy. At 700W PTC with five adjustable levels it is rated as roughly 40 percent stronger than standard models at the same class, which is how it manages a compact tent or a single room without pushing to maximum constantly.
The real differentiator is control. A high precision sensor tracks temperature and VPD in real time and adjusts output automatically, and the app handles minimum temperature, target VPD and day or night recipe programming. It also logs temperature and humidity, so you end the season with actual data on how cold your nights really get. Several growers report it replaced a much bulkier 1300W heater and did the job better.
Safety is handled properly for an indoor unit. V0 flame retardant materials, tip over protection and overheat shutoff are all built in, and the compact 9.45 inch footprint means it fits inside a tight tent or sits outside with airflow directed inward.
For a greenhouse this is genuinely useful as the bench level unit, holding a propagation area or seedling tray zone at a target while the main heater handles the air mass.
Is app control worth the extra complexity?
If you are already running sensors and scheduling in a tent, yes. The VPD targeting and day or night recipes remove guesswork, and the logging gives you a season long record. If you are simply trying to keep a greenhouse above freezing, the app adds a setup step and nothing else.
That is also the main source of complaints: WiFi pairing can be difficult to complete, and once paired the unit is generally stable.
What the wattage limits you to
700W is modest. It is sized for compact grow tents, plant rooms and single rooms, not a greenhouse volume. A 6×8 with poor insulation will simply outrun it on a cold night.
Fan noise is noticeable in a quiet room, so do not place it where you sleep. And while growers rate the results highly, several feel the price is not fully justified for the job it does.
7. Spider Farmer 530W PTC Heater – Best for Grow Tent Schedules
Spider Farmer Heater,530W 10-Level PTC Heating for Grow Tent,Plant Room
530W PTC heating
10 heat and fan levels
24 hour countdown timer
160 cm vent hose
Plus or minus 3F dead band
Pros
- Built in plus or minus 3F dead band that cuts short cycling
- 530W PTC with PWM control across 10 heat and fan levels
- Custom temperature sensor that adjusts heating and ventilation in real time
- Four modes for open running and all day daytime or night control
- 24 hour countdown timer with panel auto off after 30 seconds of inactivity
Cons
- The dead band makes temperature accuracy deliberately looser
- 530W is a modest output for anything beyond a small tent
- Digital display stays lit when active which matters for dark cycle
This heater solves a specific problem well: short cycling. Its built in plus or minus 3F dead band means it will not switch on and off every few seconds chasing a single number, which is what kills cheap heaters and causes temperature swings that stress plants. Growers who switched to it report steadier tent temperatures with fewer cycles, and most of them read the dead band as a feature rather than a flaw.
Output is 530W PTC with PWM control and ten levels for both heat and fan, on 110V at 3 amps. The included remote temperature sensor means you can place the sensor at canopy level rather than next to the heater, which is where most cheap units give you a misleading reading.
Scheduling is thorough. There are four modes covering normal open running, all day temperature control, daytime and night, plus a 24 hour countdown timer. The control panel also auto shuts off after 30 seconds of inactivity, which keeps the tent dark at night. A 160 cm adjustable vent hose is included to direct airflow away from plants.
Safety covers thermostat hardware protection plus internal and ambient over temperature protection, with flame retardant materials throughout.
How the dead band works in practice
Rather than trying to hold an exact figure, it holds a zone. If you set a target, expect to land within a few degrees of it either side. For propagation and vegetative growth that is fine, and it is better than constant cycling that dries the air and annoys the roots.
It also means you should not use this unit where you need a precise soil temperature for germination. That is a heat mat job.
Where it falls short
530W is a modest output, and it is honest about that. It is built for small tents and plant rooms, not greenhouse volumes. Owners who moved it into a larger space generally found the wattage ran out before the thermostat did.
The digital display staying lit when active is worth knowing about if you run a strict dark cycle for flowering photoperiod control, though the 30 second auto off largely handles it.
8. ProCom 10000 BTU Liquid Propane Heater – Best for Power Outages
ProCom Heating Liquid Propane Ventless Blue Flame Heater With Base Feet – 10,000 BTU, T-Stat Control – Model# ML100TBA-B
10000 BTU blue flame
T stat thermostat
ODS pilot safety sensor
No electricity needed
500 sq ft
Pros
- 10000 BTU blue flame output heating up to 500 sq ft from liquid propane
- T stat thermostat with high medium and low settings
- No electricity required so it works through a power outage
- Pilot oxygen depletion sensor shuts down on low oxygen or carbon monoxide and it is ANSI certified
- Wall mounting hardware plus base feet for freestanding use
Cons
- Ventless combustion means ventilation and air quality need thought
- The pilot flame produces a noticeable noise
- ODS sensor can trip when dirty and needs cleaning
- A minority report gas valve failure within weeks
This is the heater to buy if your power goes out mid winter, which it will eventually, or if you are off grid. It runs entirely on liquid propane with no electricity required, and 10000 BTU of blue flame output covers up to 500 square feet, roughly double the area of the radiant Buddy rated at 225 square feet.
Unlike the radiant Buddy, this one has a real thermostat. The T stat control gives you high, medium and low settings, so you can bring the output down to a pilot rather than running full output all night. Owners report consistent thermostat driven heat, low visible fumes compared with other ventless heaters, and use in RVs, small rooms and as backup heat.
Safety is the strongest part of the specification. Push button ignition is paired with a pilot oxygen depletion sensor that shuts the unit down on low oxygen or carbon monoxide detection, and the heater is ANSI certified. In a greenhouse you are deliberately sealing ventilation against frost, which is exactly when an ODS is worth having.
It is also flexible about placement. Wall mounting hardware is included, and base feet are supplied if you would rather stand it on the floor. The slim profile takes up very little bench space.
Is a ventless heater safe in a greenhouse?
It can be, with conditions. Ventless means combustion products enter the space rather than leaving through a flue, so you need a working oxygen depletion sensor, a fresh air inlet, and a rule about never sealing the structure completely. The ODS is the final safeguard, not a substitute for ventilation.
Keep the intake clear of foliage and never store fuel containers inside the greenhouse.
What to watch for
The pilot flame makes an audible noise that several reviewers mention, and it never fully goes out on low. The ODS sensor needs cleaning, since a dirty sensor can trip and cut heat at the worst moment.
A minority of buyers report gas valve failure within a matter of weeks to a month, so buy it from a seller who handles returns easily and test it before the season starts.
9. SwSun 1500W WiFi Greenhouse Heater – Best for Remote Temperature Alerts
1500W Greenhouse Heater with Thermostat WIFI APP, Heater for Outdoor Greenhouse Green House with APP Remote Control Portable Smart Electric Heat for Green Plants
1500W electric
40F to 113F range
WiFi app with SMS alerts
IPX4 metal exterior
Tip over and overheat shutoff
Pros
- WiFi app control with remote on off and scheduled timers
- SMS high and low temperature alerts when the greenhouse strays from set points
- Adjustable 40F to 113F range with a built in thermometer showing live temperature
- IPX4 rustproof metal exterior with PTC ceramic heating
- Dual heating and fan modes for year round use
- Multiple buyers report easy WiFi linking and straightforward setup
Cons
- Lowest average rating here at 3.8 with 14 percent one star reviews
- Several owners report it shutting down and not heating when real cold arrives
- Resets and does not restart on its own after a brief power interruption
- Insufficient to hold a minimum temperature in an 8x10 during multi day cold
- Oscillator can keep running when the heater is off
What makes this one interesting is the alerting. The app sends SMS high and low temperature tips to your phone when the greenhouse strays from your set points, and the unit carries a built in thermometer showing live temperature across an adjustable 40F to 113F range. For someone who is not sleeping beside the greenhouse, knowing at 5am that the temperature has collapsed is genuinely worth something.
Construction is sensible for the environment. The exterior is IPX4 rated rustproof metal with PTC ceramic heating inside, which is the right pairing for a humid space with irrigation. It runs at 1500W on a standard 120V outlet at 12.5 amps, and it has two working modes for heating and fan circulation, with the fan mode not affecting humidity.
Protections are comprehensive on paper: overheat shutoff at 65C, tip over shutoff and power failure protection. Alert ranges are separately adjustable, with a high band of 70F to 113F and a low band of 0F to 68F. The compact 7 by 2.5 by 5 inch body means it disappears onto a bench.
Several buyers report easy WiFi linking, which is not always the case with app controlled heaters. That is a real plus.
Why the rating sits lower than the rest
This is the lowest rated heater in the group at 3.8, with 14 percent of ratings at one star. The critical pattern is consistent and it is about durability rather than features: several owners describe the heater cutting out after a few months or during a cold snap, and not coming back.
There is also a specific report of it being insufficient to maintain a minimum temperature in an 8×10 greenhouse during multi day cold spells, which is a real capacity limit rather than a defect.
How to use it intelligently if you buy it
Treat it as a supplementary unit in a small, reasonably tight space, not as your primary defence. Keep the power failure protection in mind: it resets and does not restart on its own after a brief interruption, so a greenhouse on an automatic timer or a marginal supply needs a manual check after any outage.
One owner also reported the oscillator continuing to run when the heater is off, and stopping after a few weeks, so treat the fan as a secondary function.
10. Mr. Heater 30000 BTU Vent Free Radiant Heater – Best for Large Uninsulated Spaces
Mr. Heater 30,000 BTU Vent Free Radiant Propane Heater
30000 BTU propane radiant
Built in adjustable thermostat
No venting required
Low oxygen shutoff
4500 ft altitude rated
Pros
- 30000 BTU per hour rated to heat up to 1000 sq ft
- Built in adjustable thermostat with five heat settings
- Runs on propane with no electricity and no outdoor venting required
- Low oxygen safety shutoff plus battery electronic ignition with battery included
- Ceramic element version produces far less off gassing than open flame models
- Wall mounting hardware included and owners report it working at 7000 ft
Cons
- Manufacturer manual requires that it never run unsupervised
- Optional blower fan kit is sold separately and owners report it is loud and moves little air
- Very intense radiant heat very close to the unit
- Not suitable for ceiling or angled mounting
- Weighs 26.3 pounds so it is hard to relocate
This is the answer when you are heating a large structure that leaks heat, which is the situation the whole sizing conversation is really about. At 30000 BTU per hour it is rated to heat up to 1000 square feet, well beyond the 600 square feet of the widest electric unit in this roundup. It needs no outdoor venting and no electricity, only a propane supply, and it carries a 4500 ft high altitude rating with owners reporting it working at 7000 ft.
The built in adjustable thermostat with five heat settings is what lifts it above the radiant Buddy. You are not choosing between low and high, you are dialling continuously, and 78 percent of its 1434 ratings sit at five stars. Owners describe heating 1000 sq ft homes and workshops to comfortable temperatures in sub zero weather.
It is worth calling out the ceramic element version specifically. Owners of ceramic variants report far less off gassing than open flame models, which matters for anyone sensitive to combustion products and matters even more in a space you are sleeping near. The optional blower fan kit is a separate purchase, and reviewers say it is loud and moves little air, so plan your placement on radiant principles instead.
Wall mounting hardware is included, which solves the floor space problem in a packed greenhouse.
What the manual requires you to do
The manufacturer manual states that it must not be left unattended. That is not a review complaint, it is the operating condition. If you need something that manages itself overnight, this is the wrong heater and the electric units above are the right answer.
It also cannot be mounted on a ceiling or at an angle, because doing so can trigger the internal overheat sensor and shut it down. Wall mount it exactly as specified.
Who should not buy this
Anyone with a small hobby greenhouse. 30000 BTU in a 6×8 space is not a heater, it is a kiln, and the radiant heat close in is intense enough to need real caution around children and dry plant material.
It is also 26.3 pounds, which is a genuine problem if you ever need to move it. And close range radiant intensity means you should think carefully about where your benches sit relative to it.
How to Size a Greenhouse Heater
Start with insulation, not with a number. Heat loss, not heater capacity, decides whether you have a solvable problem. Single layer polycarbonate on glass loses heat so fast that no portable heater you can carry into a greenhouse will keep pace with it, and you will burn fuel all winter for a space that still drops below freezing by dawn. Rigid foam on the knee wall and base, bubble wrap or double glazing on the glazing bars, and a tight seal around the door will typically halve your heating load before you buy anything.
Thermal mass is the second lever and it is free. Water barrels, a tank, a brick wall or a bed of moist soil inside the structure absorb heat during the day and release it overnight. Growers on r/Greenhouses describe deliberately creating more of an insulating mass this way and reporting steadier overnight temperatures with a small propane heater rather than a large one.
Now do the arithmetic. A common rule of thumb in the trade is that a well insulated greenhouse needs on the order of 20000 BTU or more to reliably hold growing temperatures through winter, and that capacity has to rise as insulation falls and as your local climate gets colder. A published sizing guide makes the same point, linking required capacity directly to insulation quality and climate rather than to floor area alone.
Worked examples. A 6×8 greenhouse is 48 square feet with a modest volume, and at roughly 120 square feet of coverage the Bio Green PALMA is the correct electric match for a tight, insulated structure. An 8×12 is 96 square feet and sits at the top of what a 1500W unit can hold, which is where the Bio Green Phoenix at 215 square feet of rated coverage or the DR. INFRARED DR218 at 600 square feet rated coverage start to make sense. A 10×20 is 200 square feet with a large air volume, and in most climates that is a combustion heater job, not an electric one.
Understand the ambient floor. The single most useful real world finding from the forums is that an electric heater can hold roughly 50F inside while outside sits around 32F, and once the outside temperature drops below that, electric alone cannot hold it. That is the trigger point for switching on propane, and it is why the two stage electric plus propane approach is the dominant pattern among experienced growers.
Finally, match the electrical supply before the heater. A 1500W unit on 120V is a normal household load. A 2400W or 3000W model on 240V needs a dedicated circuit, and the DR218 specifically needs a 20A 240V outlet. If your greenhouse has one socket on an extension lead, that constraint should narrow your list before anything else does.
For comparison, indoor propane and radiant shop heat often needs nothing beyond a standard wall outlet, which is worth reading before you start planning a circuit. We have covered those categories in detail in our guides to the best patio heaters and the best radiant shop heaters.
What Type of Heater Is Most Efficient for a Greenhouse?
Infrared quartz heaters are the most efficient per watt for a greenhouse, because they warm plants and surfaces directly instead of heating all the air. But the most efficient choice overall depends on your goal: a small propagation bench wants infrared, a frost protected hobby greenhouse wants a thermostat controlled electric unit, and a large structure in a hard winter wants propane. Efficiency per watt and efficiency per night are different questions.
Electric vs Propane vs Infrared: Which Should You Buy?
Electric gives you precise, automatic control, zero combustion products and a thermostat that holds a set point without you. Its ceiling is real: roughly 1500W on a standard outlet, 2800 to 3000W with a 240V circuit, and a practical ambient floor near 32F outside. Propane ignores all of that ceiling and burns through cold nights reliably, but it is unattended-unfriendly, needs cylinders, and every unit is a combustion device in a space you are sealing against frost. Infrared and radiant heat warms surfaces and plants rather than air, which is efficient for a bench or a row of citrus and wrong for raising the temperature of an entire structure.
The recommendation matrix is short. Small greenhouse, mild winters, frost protection only: the Bio Green PALMA on 1500W. Mid-size greenhouse, moderate winters, insulated: the Bio Green Phoenix or the DR. INFRARED DR218 with a 240V circuit. Propagation benches and tents inside the greenhouse: the VIVOSUN AeroFlux or Spider Farmer units, sized to the tent rather than the greenhouse. Hard winters, large or leaky structures: propane, either the ProCom with its thermostat and oxygen depletion sensor, or the Mr. Heater 30000 BTU where the area is genuinely large.
On running economics, the honest comparison is not between the fuels in the abstract but between hours of operation. Electric load scales directly with time and a thermostat minimises it, while propane consumes a cylinder regardless. A 3000W radiant unit on high drew about 7 kWh across one reported night holding an 8×12 greenhouse at 38 to 39F, which is a useful benchmark for planning. Propane radiant units are measured differently, with the Buddy running 2.4 hours on high or 5.4 hours on low from a 1 lb cylinder.
The efficient answer in practice is usually the two stage setup: electric on the thermostat for the majority of nights, propane for the handful of nights that would otherwise lose the crop. If you are also considering heating a building rather than a frame, our guides to the best electric tankless water heaters cover a different kind of heating decision entirely.
Heater Placement and Airflow: The Most Reported Mistake
Placement is the single most reported source of disappointment, and it is free to fix. Put the heater low and at one end, not centred and not overhead, so the warm air travels the length of the structure and the cold air that settles along the glazing has somewhere to fall away from the canopy. If your heater has a fan, aim it along the benches rather than across them.
Keep at least a foot of clear air around the outlet and around the body. Owners report the overheat alert sounding in well insulated structures precisely because clearance was tight. Suspended mounting, where the hardware allows it, is usually the best answer in a tall greenhouse.
Then fight the dead zone. A heater at ridge height warms air that never reaches the root zone, and a bench sitting in that cold pocket will not grow no matter what the thermometer near the roof reads. Measure at bench height, not at the ridge.
Safety First: Combustion Heat Inside a Sealed Greenhouse
Ventless and radiant propane heaters produce combustion products indoors by design, and a greenhouse in winter is a space you have deliberately closed up. The Buddy addresses this with an emergency low oxygen safety system and self extinguishing construction. The ProCom goes further, with a pilot oxygen depletion sensor that shuts the unit down on low oxygen or carbon monoxide detection plus ANSI certification.
Ventilation is still required. Provide a fresh air inlet, keep the sensor clean, and never run a combustion heater in a completely sealed structure. The sensor is a final safeguard, not a substitute for air. Do not store fuel cylinders inside the greenhouse.
On the electrical side, confirm the circuit rating matches the heater, use outdoor rated extension leads for any run outside, and keep all connections away from irrigation water. IPX4 rated housings like the PALMA, the DR218 and the SwSun tolerate damp conditions far better than IP20 models such as the VEVOR.
And clear the combustibles. Radiant output is intense at close range, so keep the propane units away from dry foliage, plastic sheeting and mulch, and make sure the 30,000 BTU model is wall mounted as specified and never ceiling mounted.
Should You Even Heat Your Greenhouse?
Sometimes no, and the gardening forums are blunt about it. The consensus on r/gardening is that most hobby greenhouses are structurally inefficient for winter heating, and that the better move is to dedicate a room or a basement area instead. A basement with a bench, a light and a heat mat costs a fraction of what it takes to hold a leaky frame above freezing.
Cheaper alternatives worth considering before you buy capacity, in rough order of cost: heavy mulch over root zones, thermal mass barrels, a low tunnel set up inside the greenhouse to shrink the space you actually heat, rigid foam insulation panels, and closing the greenhouse at dusk to trap the day’s stored heat.
Heating makes sense when you have something genuinely temperature sensitive in there, such as overwintering citrus and figs, propagating cuttings, or keeping greens growing through the cold months. If you are only protecting a few hardy perennials, a cold frame or an unheated structure may be the right answer.
Frequently Asked Questions
What type of heater is most efficient for a greenhouse?
Infrared and radiant heat is the most efficient per watt because it warms plants and surfaces rather than heating all the air. The most efficient overall choice depends on the job: a propagation bench wants infrared, a frost-protected hobby greenhouse wants a thermostat-controlled electric unit, and a large structure in a hard winter wants propane. Per-watt efficiency and cost per night are different questions.
What’s better, an electric or propane heater?
Electric wins on control, safety and unattended operation because a thermostat cycles it automatically and there are no combustion products. Propane wins on raw output and cold weather reach, burning reliably when outside temperatures fall toward freezing. In practice most experienced growers run both, using electric on the thermostat for ordinary nights and propane only when the temperature drops.
What is the best propane gas heater for a greenhouse?
The Mr. Heater Buddy 9000 BTU is the best all-round propane choice, with 29212 ratings averaging 4.7, two output settings, a low oxygen safety shutoff and coverage of roughly 225 square feet. For larger areas or when you need a thermostat, the ProCom 10000 BTU adds T-stat control, an oxygen depletion sensor and no-electricity operation, while the Mr. Heater 30000 BTU covers up to 1000 square feet.
What is the best electric greenhouse heater?
The Bio Green PALMA 1500W is the best electric greenhouse heater for most hobby growers, with a digital thermostat, two separately adjustable elements, a fan-only circulation mode, IPX4 splash proof housing and 3393 ratings. For bigger structures, the Bio Green Phoenix at 2800W covers up to 215 square feet, and the DR. INFRARED DR218 at 3000W is rated to 600 square feet, both requiring a 240V circuit.
What is the best 1500W electric heater?
For a greenhouse the VEVOR 1500W PTC is the budget answer, delivering 5100 BTU with overheat protection and a three speed knob, though control is coarse and the IP20 housing gives less splash protection. For precise control at the same wattage, the Bio Green PALMA 1500W adds a digital thermostat, IPX4 housing and a fan-only mode, which is why it is our first pick overall.
How do I keep my greenhouse warm during winter?
Reduce heat loss before adding capacity. Insulate the base and knee wall with rigid foam and double glaze the glazing bars, then add thermal mass such as water barrels or a brick wall. Size a thermostat-controlled electric heater to your floor area, position it low at one end so warm air travels the length of the structure, and measure temperature at bench height. Add propane for nights when outside temperatures fall near freezing.
What is the cheapest way to heat a greenhouse in the winter?
Ranked by cost, the cheapest options come first. Use thermal mass such as filled water barrels and a heavy mulch over root zones. Set a low tunnel inside the greenhouse to shrink the space you actually heat. Add rigid foam panels to the base and knee wall. Run a small thermostat-controlled PTC unit such as a 530W or 700W model for a propagation bench. Heat only what must stay alive, and move tender plants indoors when temperatures drop hard.
How do the Amish heat their greenhouses?
Amish growers generally avoid heating a greenhouse at all, relying instead on unheated high tunnels, careful siting, thermal mass and cold-hardy varieties chosen for the local zone. Where heat is needed it comes from small wood or rocket mass heater builds rather than purchased electric or propane units. The transferable lesson is that passive retention and choosing the right structure matter more than purchased capacity.
The Bottom Line
If you want one answer, the Bio Green PALMA 1500W is the best greenhouse heater for winter growing in 2026 for a small to mid-size structure, because a real thermostat plus IPX4 splash proofing plus a fan-only mode is the combination that survives a season. Add a Mr. Heater Buddy 9000 BTU propane unit as your cold snap backup and you match the two stage pattern experienced growers describe: electric on the thermostat for ordinary nights, propane for the nights when outside temperatures approach freezing.
Before either one goes in the shed, spend a weekend on insulation and thermal mass. The heater you can afford works far harder in a structure that is not bleeding heat through every panel, and if the numbers still do not work, moving tender plants to a dedicated room is a legitimate answer rather than a failure.