Keeping a greenhouse productive through winter means holding a steady temperature above freezing—or even above 50°F for tender crops. Gas-fired heaters deliver raw British Thermal Units (BTUs) faster than electric resistance units, and they keep running when the grid goes down. But picking the wrong BTU rating, fuel type, or safety configuration can burn your plants or your wallet.
I’m Mohammad Maruf — the founder and writer behind Gardening Beyond. I’ve spent years comparing heating specifications, studying horticultural temperature data, and analyzing aggregated owner feedback to identify which gas greenhouse heaters actually perform in real-world growing environments.
Whether you need a compact unit for a hobby greenhouse or a high-BTU forced-air beast for a commercial setup, this guide dissects the top contenders to help you find the best gas greenhouse heaters for your growing space.
How To Choose The Best Gas Greenhouse Heaters
Selecting a gas greenhouse heater isn’t about picking the highest BTU number. You need to balance heat output, fuel type, safety features, and airflow style to match your greenhouse’s size, construction, and plants.
BTU Rating and Greenhouse Volume
BTU (British Thermal Unit) measures heat output. A general rule is 20 to 30 BTUs per square foot in mild climates, but uninsulated poly tunnels in northern zones can demand 50+ BTUs per square foot. Measure your greenhouse’s total cubic footage, not just floor area—higher ceilings require more heat. An undersized unit runs continuously and never reaches target temperature. An oversized unit short-cycles, creating temperature swings that stress plants.
Fuel Type: Propane vs. Natural Gas
Propane tanks (typically 20-pound or 100-pound cylinders) offer portability and off-grid capability—critical for remote greenhouses. Natural gas requires a permanent gas line but eliminates tank refills and usually costs less per BTU. Most propane units accept a natural gas conversion kit, but always check manufacturer compatibility before switching.
Heating Method: Radiant vs. Forced Air vs. Convection
Radiant (infrared) heaters warm objects and plants directly without drying the air, making them gentle for seedlings and propagation. Forced-air units blow hot air, distributing warmth quickly across large spaces—better for big greenhouses but can dessicate foliage if aimed directly at plants. Convection heaters rely on natural airflow and are silent but slower to distribute heat. Ventless radiant units conserve heat inside the greenhouse, while vented models expel combustion gases outside—safer for enclosed spaces but less efficient.
Safety Certifications You Must Not Ignore
An Oxygen Depletion Sensor (ODS) automatically shuts off the heater if oxygen levels drop too low, preventing carbon monoxide buildup. Tip-over protection cuts gas flow if the unit is knocked over—essential near workbenches or foot traffic. For indoor (enclosed greenhouse) use, only units labeled “indoor safe” or “ventless” with ODS should be considered. Forced-air units are typically rated for outdoor or well-ventilated areas only.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Mr. Heater MH200CVX | Premium | Large greenhouses (up to 5,000 sq ft) | 200,000 BTU convection | Amazon |
| Mr. Heater QBT 170K | Premium | Quiet forced-air heating | 170,000 BTU forced air | Amazon |
| Mr. Heater 20K Natural Gas | Mid-Range | Small greenhouses (up to 700 sq ft) | 20,000 BTU ventless | Amazon |
| ProCom MN100TBA-B | Mid-Range | Natural gas users, wall-mount | 10,000 BTU natural gas | Amazon |
| Gasland MHA18BN | Mid-Range | Portable cabinet radiant | 18,000 BTU radiant | Amazon |
| Remington LP Forced Air | Mid-Range | Garages and workshops | 60,000 BTU forced air | Amazon |
| Ruasveltan Cabinet Heater | Budget | Small spaces, entry-level | 18,000 BTU radiant | Amazon |
| OKF Propane Heater | Budget | Budget-friendly portable | 18,000 BTU radiant | Amazon |
| WELLUCK Cabinet Heater | Budget | Portability and quiet | 18,000 BTU radiant | Amazon |
In-Depth Reviews
1. Mr. Heater MH200CVX 200,000 BTU Convection Propane Heater
The Mr. Heater MH200CVX is a convection-style propane heater that pushes an enormous 200,000 BTUs, covering up to 5,000 square feet—enough for a multi-bay commercial greenhouse. Its convection method circulates heat without a noisy fan, which means less dust disturbance and a more gradual temperature rise that tender plants tolerate well. The piezo push-button igniter fires reliably, and the single control knob lets you dial heat from 75,000 to 200,000 BTUs, giving you fine-grained control over your greenhouse environment.
Safety is robust: a thermo-electric safety valve shuts the gas flow the instant the flame goes out, and the unit requires a 100-pound tank for extended runtime—up to 29 hours on low. The 10-foot hose and regulator are included, so setup is straightforward. At 19.2 pounds, it’s surprisingly portable for its output, though the sheer heat requires good ventilation in the greenhouse to avoid stressing plants with direct radiant exposure.
For large-scale growers who need raw heat output and convection’s gentle warmth, the MH200CVX delivers unmatched coverage per dollar. It’s not for small hobby greenhouses—the minimum 75,000 BTU output would overwhelm a 200-square-foot space. But for serious operations, this is the workhorse.
What works
- Massive 200,000 BTU covers 5,000 sq ft
- Convection heating is silent and gentle on plants
- Variable output from 75,000 to 200,000 BTUs
What doesn’t
- Overkill for small greenhouses under 1,000 sq ft
- Requires a 100-pound tank for long runtime
- Ventilation must be managed carefully
2. Mr. Heater 170,000 BTU Quiet Burner Technology Forced Air Propane Heater
Mr. Heater’s Quiet Burner Technology (QBT) sets this forced-air propane unit apart—it operates roughly 50 percent quieter than standard forced-air heaters, making it tolerable in greenhouses near homes or where noise carries. The 170,000 BTU output heats approximately 4,000 square feet, ideal for medium-to-large commercial greenhouses, barns, or workshops. The automatic solid-state ignition ensures reliable starts even in cold conditions, and the high-temperature limit switch prevents overheating.
On a 100-pound propane tank at the low setting, it runs up to 17 hours—enough for overnight protection during freeze warnings. Because it’s forced air, heat distribution is fast and even, but you’ll want to aim the airflow away from direct plant contact to avoid leaf desiccation. The unit is rated for outdoor/well-ventilated areas, so ensure your greenhouse has adequate air exchange.
At 18 pounds, it’s lighter than many comparable forced-air units, and the handle makes it easy to reposition. If you need powerful heat with significantly less noise than a conventional propane torpedo heater, the QBT model is a smart upgrade.
What works
- 50% quieter than standard forced-air heaters
- 170,000 BTU covers 4,000 sq ft quickly
- Solid-state ignition starts reliably in cold
What doesn’t
- Forced air can dry out foliage if aimed wrong
- Needs good ventilation—not for sealed greenhouses
- 17-hour max runtime requires big tank
3. Mr. Heater 20,000 BTU Vent Free Blue Flame Natural Gas Heater
This ventless natural gas heater from Mr. Heater produces 20,000 BTUs and covers up to 700 square feet, making it a strong candidate for mid-sized hobby greenhouses. The blue flame technology heats the air directly via convection, creating an even temperature without a fan—ideal for maintaining steady conditions around sensitive seedlings. The built-in adjustable thermostat lets you set your target temperature, and the battery-operated electronic ignition (one AA battery included) works during power outages.
Because it’s ventless, all heat stays inside the greenhouse—no energy wasted out a flue. The unit is indoor-safe, with an ODS that shuts it down if oxygen drops. Mounting hardware for wall installation is included, saving floor space in cramped greenhouses. At 19.6 pounds, it’s solid but not overly heavy, and the white cabinet fits neatly into a greenhouse aesthetic.
The natural gas connection requires a permanent line, which adds installation cost but eliminates tank refills. For growers with existing natural gas access who want a reliable, thermostat-controlled heater that doesn’t need electricity, this is a top contender.
What works
- Ventless operation keeps 100% of heat inside
- Thermostat control maintains steady temps
- Wall-mountable to save floor space
What doesn’t
- Requires natural gas line installation
- Blower fan kit sold separately for circulation
- 20,000 BTU max may be low for uninsulated greenhouses in cold zones
4. ProCom MN100TBA-B Ventless Natural Gas Blue Flame Space Heater
The ProCom MN100TBA-B delivers 10,000 BTUs of ventless natural gas heat—perfect for small greenhouses, propagation sheds, or overwintering setups up to 500 square feet. Its compact, slim profile (just 6.38 inches deep) mounts on a wall or sits on included base feet, making it unobtrusive. The thermostat control offers High, Medium, and Low settings, so you can match output to ambient conditions without constant adjustment.
Safety is handled by a built-in pilot ODS that immediately shuts down the heater if carbon monoxide or low oxygen is detected. The push-button ignition is simple and reliable. No electricity is required, so it’s fully operational during power outages—a real advantage for greenhouse growers in storm-prone areas. The white finish blends into most greenhouse interiors nicely.
The trade-off for this compact size is the BTU ceiling: 10,000 BTUs will only keep a small, well-insulated space warm on mild winter nights. In northern climates with deep freezes, you may need a second unit or supplemental heating. But for a small greenhouse or cold frame, the ProCom is an efficient, space-saving solution.
What works
- Ultra-compact and wall-mountable
- Thermostat control with 3 heat settings
- Fully operational without electricity
What doesn’t
- 10,000 BTU insufficient for large or uninsulated greenhouses
- Natural gas only—no propane option
- Pilotless design may need periodic recalibration
5. Gasland MHA18BN Propane Radiant Heater
The Gasland MHA18BN is a cabinet-style radiant propane heater that offers 18,000 BTUs of infrared heat, warming up to 450 square feet—ideal for a small-to-medium hobby greenhouse. Radiant heat warms plants and soil directly without drying the air, which is gentler on transpiration-sensitive crops like seedlings and leafy greens. The three heating modes (6,000, 12,000, and 18,000 BTU) let you fine-tune output, and the built-in rolling wheels and carry handle make repositioning simple.
Safety features include tip-over protection and an ODS that automatically cuts off the gas if oxygen levels drop. The LP tank hides inside the cabinet, keeping the greenhouse tidy and reducing trip hazards. No electricity is required—just connect a standard 20-pound propane cylinder. Customer feedback consistently notes the near-silent operation, which is a significant advantage over fan-forced units.
The 450-square-foot coverage is realistic for a sealed, insulated greenhouse; drafty poly tunnels will need more BTUs. At this price point, the MHA18BN offers excellent value for dedicated hobbyists who want quiet, radiant warmth without a permanent gas line installation.
What works
- Radiant heat is gentle on plants and soil
- Three adjustable heat settings for temp control
- Near-silent operation at under 30 dB
What doesn’t
- Coverage limited to 450 sq ft
- Not for uninsulated or drafty greenhouses
- Propane tank sits inside cabinet—reduces internal space
6. Remington LP Forced Air Heater
The Remington LP Forced Air Heater brings 60,000 BTUs of directed heat to spaces up to 1,500 square feet—a fit for larger hobby greenhouses or workshop-connected growing areas. Its forced-air design pushes warm air quickly across the space, reducing cold spots in longer greenhouses. The heavy-duty steel construction and 11-pound weight make it rugged and portable, with a pedestal form factor that stands securely on uneven ground.
Variable heat settings and adjustable height let you customize the heat pattern, while safety features include a thermocouple, high-temperature limit shut-off, and flame-out fuel cut-off. The electronic ignition starts reliably, and the included 10-foot LP cylinder hose and regulator simplify setup. It runs on a standard 20-pound propane tank (not included).
One limitation: this unit is rated for outdoor or well-ventilated indoor use, meaning your greenhouse needs active ventilation to avoid combustion gas buildup. The forced air can also create drafts that stress young plants, so directional aiming is critical. For greenhouses that double as workspaces, though, the Remington delivers quick, powerful heat when you need it.
What works
- 60,000 BTU quickly warms 1,500 sq ft
- Adjustable height and heat settings
- Rugged steel build for demanding environments
What doesn’t
- Forced air requires active ventilation
- Airs can dry out foliage if directed poorly
- Heavy for its size at 11 pounds, but not cabinet-portable
7. Ruasveltan Propane Heater Indoor and Outdoor
Ruasveltan’s cabinet propane heater delivers 18,000 BTUs across three adjustable modes, covering up to 450 square feet—adequate for a small hobby greenhouse or propagation tent. The radiant ceramic panel emits infrared heat that warms plants directly without stirring up dust or drying the air, which is advantageous for humidity-loving crops. The piezoelectric ignition fires reliably without batteries or electricity, keeping the unit fully off-grid.
The cabinet design is lightweight at 13.8 pounds, with a wide fixed stand that provides stability on soil or concrete floors. The dual safety system—ODS and tip-over shutoff—meets basic greenhouse safety requirements. The unit’s ultra-thin profile makes it easy to store when not in use. At the low 6,000 BTU setting, it can run up to 69 hours on a 20-pound tank, offering extended runtime for overnight freeze protection.
The trade-off for the entry-level price is build quality: some users report less durable construction compared to premium brands, and the 450-square-foot coverage assumes a well-insulated space. In drafty greenhouses, you’ll likely need the high setting, which reduces runtime. For a budget-conscious first-time greenhouse heater, though, the Ruasveltan is a functional starting point.
What works
- Affordable entry into gas greenhouse heating
- Radiant heat is gentle on plants
- Up to 69 hours runtime on low setting
What doesn’t
- Build quality feels less robust than premium options
- 450 sq ft assumes good insulation
- Limited to 18,000 BTU max output
8. OKF Propane Heater
The OKF propane heater uses a pulse ignition system, which is more durable and reliable than traditional piezo starters—no repeated clicking to get a flame. It delivers 6,000 to 18,000 BTUs across three modes, heating up to 450 square feet with radiant infrared warmth. The cabinet on casters includes four wheels with brakes, making it easy to roll across greenhouse floors and lock in place. The LP tank stores discreetly inside the cabinet, keeping the footprint clean.
Noise levels are impressively low at below 30 decibels—essentially silent, which matters in a greenhouse where constant fan hum can be disruptive during quiet work sessions. Dual safety protection (ODS and tip-over shutoff) provides the expected safeguards. On low setting, the OKF runs up to 69 hours on a 20-pound tank, and the regulated hose is included for immediate setup.
The main limitation is shared with other cabinet-style radiant heaters: the 450-square-foot coverage is realistic for sealed greenhouses but falls short in uninsulated or high-ceiling structures. The OKF is also on the heavier side among cabinet units at approximately 27 pounds, though the casters compensate. For growers prioritizing easy mobility and pulse ignition reliability, this is a solid mid-range pick.
What works
- Pulse ignition is more durable than piezo
- Four locking casters for easy movement
- Near-silent operation at under 30 dB
What doesn’t
- Heavier than similar cabinet units
- Coverage drops in uninsulated spaces
- Max output still 18,000 BTU
9. WELLUCK Propane Heater Indoor Outdoor
The WELLUCK propane heater stands out with a foldable design and two 360-degree swivel casters, allowing it to compress for storage against a wall or under a bench—a rare feature in the cabinet heater category. Its 18,000 BTUs heat 450 square feet across three settings (6,000, 12,000, and 18,000 BTU), and the radiant heating element warms plants without drying the air. The ODS and tip-over protection meet standard safety expectations for enclosed greenhouse use.
At 32 decibels, it’s marginally louder than the OKF but still whisper-quiet—you won’t notice it running during daily gardening tasks. The unit operates without electricity, connecting to a standard 20-pound propane tank. On low, it runs up to 69 hours, making it suitable for overnight freeze protection. The foldable frame collapses to a much smaller footprint, which is a genuine advantage for small greenhouses where every square inch counts.
Like other budget-tier cabinet radiants, the 450-square-foot rating assumes a sealed, insulated space. The build quality is good for the price tier, but long-term durability against the humidity and condensation typical in greenhouses remains unproven. For growers with limited storage space who want a quiet, effective propane heater that stows easily between seasons, the WELLUCK is a smart choice.
What works
- Foldable design saves storage space
- Dual swivel casters for easy maneuverability
- Quiet 32 dB operation
What doesn’t
- Coverage realistic only for insulated greenhouses
- Long-term humidity resistance unknown
- No thermostat—manual gas knob adjustment only
Hardware & Specs Guide
Heating Method: Radiant vs. Forced Air vs. Convection
Radiant (infrared) heaters warm objects and soil directly without heating the air, which reduces moisture loss and is ideal for seedlings, propagation, and humidity-loving crops. Forced-air heaters use a fan to blow hot air across the space, distributing heat faster—better for large greenhouses but can dry out foliage if directed poorly. Convection heaters rely on natural air currents, offering silent operation with slower, more even heat distribution. Choose radiant or convection for plant-sensitive areas; forced air is best for large structures where fast temperature recovery is critical.
BTU Sizing: Matching Output to Your Greenhouse
Calculate your greenhouse’s total cubic volume (length × width × average height) and use 20–30 BTUs per cubic foot in mild winter climates, and 40–60 BTUs per cubic foot in zones with sustained freezing temperatures. An undersized heater runs continuously without reaching set point; an oversized heater short-cycles, causing temperature swings that stress plants and waste fuel. Always size conservatively—it’s better to run a properly sized heater on a lower setting than to overshoot and struggle with temperature fluctuations.
FAQ
Can I use a forced-air propane heater in a sealed greenhouse?
How many BTUs do I need for a 10×12 greenhouse?
What does ODS protection mean for a greenhouse heater?
Final Thoughts: The Verdict
For most gardeners, the best gas greenhouse heaters winner is the Mr. Heater MH200CVX because it delivers massive 200,000 BTUs of convection heat across 5,000 square feet with a silent, gentle warmth that won’t dry out your plants. If you need a quieter forced-air option for a large greenhouse, grab the Mr. Heater 170,000 BTU QBT. And for a compact, ventless natural gas heater in a small greenhouse, nothing beats the Mr. Heater 20,000 BTU Natural Gas.