Complete the kit
Key Takeaways
- The highest BTU output doesn’t always mean better for backup use—size and fuel efficiency matter for sustained use.
- Safety features like oxygen depletion sensors (ODS) and tip-over shutoffs are critical in backup scenarios, especially in enclosed spaces.
- Portability varies significantly; some heaters are designed for easy transport, while others are best kept stationary for emergency backup.
- Venting and vent-free designs influence installation flexibility and safety considerations—ventless models are easier to set up but may require more caution.
- Price range varies widely; investing in a heater with better safety and efficiency features may save costs over time.
| Mr. Heater 80,000 BTU Convection Heater Portable Propane |  | Best Overall for Large Outdoor or Indoor Spaces | BTU per hour: 80,000 | Heating area: up to 2,000 sq. ft. | Fuel type: Propane | VIEW LATEST PRICE | See Our Full Breakdown |
| Mr. Heater 9,000 BTU Portable Buddy Radiant Propane Heater |  | Best for Small Spaces and Portability | BTU: 9,000 | Heat coverage: 225 sq ft | Fuel type: Propane | VIEW LATEST PRICE | See Our Full Breakdown |
| Propane Heater Indoor and Outdoor, 18000 BTU Patio Heater with Safety Features |  | Best for Versatile Indoor/Outdoor Use with Adjustable Settings | Heating Output: 18000 BTU | Heating Range: 450 sq ft | Fuel Type: Propane | VIEW LATEST PRICE | See Our Full Breakdown |
| Portable Propane Forced Air Heater |  | Best for Large Area, High-Output Heating | BTU: 125,000 | Heating Area: 3,125 sq ft | Fuel Type: Propane | VIEW LATEST PRICE | See Our Full Breakdown |
| ProCom Heating Liquid Propane Ventless Blue Flame Heater – 30,000 BTU, Manual Control |  | Best for Power Outage and Indoor Backup Heating | BTU: 30,000 | Heating area: 1400 sq ft | Fuel type: Propane | VIEW LATEST PRICE | See Our Full Breakdown |
| ROVSUN 18000 BTU Portable Propane Heater for Indoor & Outdoor Use with ODS |  | Best Overall for Versatility and Runtime | Model: RS-HCG | Fuel Type: Propane (LP Gas) | Max Heating Output: 18,000 BTU/Hr | VIEW LATEST PRICE | See Our Full Breakdown |
| Mr. Heater Big Buddy PRO Series Heater |  | Best for Larger Spaces and Extended Use | Heating Coverage: 450 sq ft | BTU: 18,000 | Fuel Type: Propane | VIEW LATEST PRICE | See Our Full Breakdown |
| ProCom Liquid Propane Ventless Ice House Heater – 10,000 BTU, Thermostat Control |  | Best for Small, Ventless, Outdoor or Ice House Spaces | Technology: 10,000 BTU Liquid Propane | Safety Features: Oxygen Depletion Sensor, auto shut-off | Heating Area: Up to 300 sq ft | VIEW LATEST PRICE | See Our Full Breakdown |
| Mr. Heater 30,000 BTU Vent-Free Radiant Propane Heater |  | Best for Power and Indoor Comfort in Large Spaces | Heat Output: 30,000 BTU/hr | Heating Coverage: 750-1,000 sq ft | Fuel Type: Propane | VIEW LATEST PRICE | See Our Full Breakdown |
| Mr. Heater 30,000 BTU Vent-Free Blue Flame Dual Fuel Heater |  | Best Dual Fuel Flexibility for Versatile Backup Heating | Heat Output: 30,000 BTU/hr | Heating Coverage: 1,000 sq ft | Fuel Type: Propane, Natural Gas | VIEW LATEST PRICE | See Our Full Breakdown |
| MOZODAWN 2-in-1 Propane Heater & Stove, 13000 BTU Portable Outdoor Heater for Camping, Tent, Ice Fishing, Garage |  | Best for Multi-Function Outdoor Use | Heat Output: 13,000 BTU | Heating Type: 360-degree radiant | Interface: Stainless steel threaded | VIEW LATEST PRICE | See Our Full Breakdown |
| propane greenhouse heater for backup heat | Fuel type |
|---|---|
| Mr. Heater 80,000 BTU Convecti | Propane |
| Mr. Heater 9,000 BTU Portable | Propane |
| Propane Heater Indoor and Outd | Propane |
| Portable Propane Forced Air He | Propane |
| ProCom Heating Liquid Propane | Propane |
| ROVSUN 18000 BTU Portable Prop | Propane (LP Gas) |
| Mr. Heater Big Buddy PRO Serie | Propane |
| ProCom Liquid Propane Ventless | Propane |
| Mr. Heater 30,000 BTU Vent-Fre | Propane |
| Mr. Heater 30,000 BTU Vent-Fre | Propane, Natural Gas |
| MOZODAWN 2-in-1 Propane Heater | — |
More Details on Our Top Picks
Mr. Heater 80,000 BTU Convection Heater Portable Propane
This heater stands out for its impressive 80,000 BTU output, capable of heating up to 2,000 square feet, making it ideal for large outdoor areas or expansive indoor spaces where reliable backup heat is needed. Compared with the Portable Buddy, it offers significantly more power, but this comes with added weight and the requirement for outdoor or garage setups. Its convection design ensures even heat distribution, and being fully assembled with safety features like a standing pilot and shut-off valve, it combines convenience with safety. However, its size and weight limit portability, and it demands a propane tank and outdoor connection, so it’s not suited for small or indoor-only environments.
Pros:- Extremely high heating capacity up to 80,000 BTU for large areas
- Operates quietly and odorlessly, suitable for outdoor or large indoor spaces
- Fully assembled with hose and regulator, ready to use
Cons:- Requires outdoor setup and propane tank, limiting indoor use
- Heavy weight (13.4 pounds) reduces portability
- Limited to outdoor or large indoor spaces, not suitable for small rooms
Best for: Property owners needing a powerful, reliable backup heat source for large outdoor or workshop areas
Not ideal for: Small residential spaces or indoor environments without outdoor access, due to its size and ventilation needs
- BTU per hour:80,000
- Heating area:up to 2,000 sq. ft.
- Fuel type:Propane
- Maximum temperature:120°F
- Item dimensions:15.75″D x 16.93″W x 21.81″H
- Item weight:13.4 pounds
- Heating method:Convection
- Coverage:2000 sq. ft.
Our verdict“This heater is best suited for users needing robust backup heat in large outdoor or workshop environments who can handle its size and setup requirements.”
Mr. Heater 9,000 BTU Portable Buddy Radiant Propane Heater
The Portable Buddy offers a compact, 9,000 BTU output, perfect for heating small to medium-sized areas up to 225 square feet, such as patios or small workshops. Its radiant heat provides quick warmth directly to people or objects, making it more efficient in targeted spaces than larger convection heaters like the Mr. Heater 80,000 BTU. It connects easily to a 1-lb propane cylinder, and safety features like oxygen depletion sensors and thermal shut-down enhance its appeal for personal outdoor use. The main tradeoff is its limited runtime—around 3 hours at high setting—and its suitability only for small, contained areas. Compared to the larger convection heater, it sacrifices power for portability and ease of use.
Pros:- Provides effective radiant heat for small to medium spaces
- Features safety systems like oxygen depletion sensor and thermal shut-down
- Connects easily to standard propane cylinders, portable for outdoor use
Cons:- Limited runtime (around 3 hours on a 1-lb cylinder at high), requiring frequent refills
- Limited heating coverage, not suitable for large areas
- Requires careful handling of propane and safety precautions
Best for: Campers, homeowners with small outdoor patios, or those needing portable backup heat
Not ideal for: Large outdoor spaces or big indoor areas, as it cannot deliver enough heat or run long enough for those situations
- BTU:9,000
- Heat coverage:225 sq ft
- Fuel type:Propane
- Max temperature:900 °F
- Number of speeds:2
- Warranty:Product Warranty
Our verdict“Ideal for portable, targeted heating in small outdoor or indoor spaces where ease of use and safety are priorities.”
Propane Heater Indoor and Outdoor, 18000 BTU Patio Heater with Safety Features
This heater provides 18,000 BTU, striking a balance between power and portability, suitable for heating up to 450 square feet. Its adjustable heat modes and safety features like oxygen depletion shutoff and tip-over protection make it a flexible choice for patios, garages, or camping. Compared with high-capacity models like the 80,000 BTU convection heater, it offers less power but more versatility for smaller spaces and safer indoor use. Its portability and safety features make it a practical backup for occasional use, though it requires a 20-lb propane tank, limiting mobility for some outdoor scenarios. It’s best for small to medium spaces where safety and adjustability matter most.
Pros:- Adjustable heat settings for customized comfort
- Safe for indoor and outdoor use with safety shutoffs
- Portable and space-saving design
Cons:- Requires a 20-lb propane tank, which adds bulk and limits portability
- Limited to heating up to 450 sq ft, not suitable for large areas
- Potential safety concerns if not used according to instructions
Best for: Homeowners needing a versatile, safe backup heater for patios or garages
Not ideal for: Large outdoor spaces or for use as primary heating in big areas, due to its limited BTU output
- Heating Output:18000 BTU
- Heating Range:450 sq ft
- Fuel Type:Propane
- Number of Heating Modes:3
- Safety Features:ODS & Tip-over
- Color:Black
Our verdict“A good choice for small to medium spaces needing adjustable, safe backup heat with indoor/outdoor flexibility.”
Portable Propane Forced Air Heater
This forced air heater delivers an impressive 125,000 BTU, capable of warming up to 3,125 square feet, making it suitable for large garages, workshops, or outdoor zones where reliable backup heat is essential. Its forced air design heats quickly and evenly, outperforming radiant-only models like the Portable Buddy in large, open environments. Despite its high power, it’s still portable, with a manageable weight of 19.4 pounds, and runs on standard propane tanks. The main tradeoffs involve its lack of a built-in thermostat, requiring manual control, and the need for proper ventilation to handle exhaust fumes safely. Compared to smaller, lower BTU heaters, this model prioritizes space coverage over finesse, making it ideal for users who need serious heat in large areas.
Pros:- Exceptional heat output of 125,000 BTU for large areas
- Portable with easy mobility
- Uses standard propane tanks, no special setup needed
Cons:- No built-in thermostat, manual adjustments required
- Heavy weight may limit frequent moving
- Requires proper ventilation due to exhaust fumes
Best for: Construction sites, large garages, or outdoor zones needing robust backup heating in cold conditions
Not ideal for: Small indoor spaces or environments where precise temperature control is a priority, due to no thermostat
- BTU:125,000
- Heating Area:3,125 sq ft
- Fuel Type:Propane
- Heating Method:Forced Air
- Item Dimensions:9.84″D x 25.83″W x 15.28″H
- Item weight:19.4 pounds
Our verdict“Best suited for large, open spaces where powerful, reliable backup heat is necessary and manual control is acceptable.”
ProCom Heating Liquid Propane Ventless Blue Flame Heater – 30,000 BTU, Manual Control
This ventless heater offers 30,000 BTU, capable of warming spaces up to 1,400 square feet without electricity, making it a strong backup during power outages. Its blue flame design provides a steady, comfortable heat, and safety features like oxygen depletion sensor and manual controls add reassurance. Compared with the larger convection heater, it excels in indoor safety and convenience, especially where electrical power may be interrupted. However, it requires professional installation and the blower is sold separately, which slightly complicates setup. Its limited BTU compared to larger outdoor units means it’s best for smaller indoor spaces or as a supplemental heat source rather than primary, large-area heating.
Pros:- No electricity needed, perfect for power outages
- Adjustable heat with three settings for comfort control
- Features safety sensors like oxygen depletion detection
Cons:- Blower must be purchased separately, adding cost and complexity
- Requires professional installation for safe operation
- Limited to indoor use and moderate space coverage
Best for: Homeowners seeking reliable, ventless backup heat during outages or in spaces without electrical supply
Not ideal for: Large open outdoor areas or spaces requiring high BTU heating, due to its moderate output
- BTU:30,000
- Heating area:1400 sq ft
- Fuel type:Propane
- Control type:Manual
- Safety features:Oxygen Depletion Sensor
- Form factor:Pedestal
Our verdict“A dependable indoor backup heater that performs well without electricity, ideal for small to medium indoor spaces during outages.”
ROVSUN 18000 BTU Portable Propane Heater for Indoor & Outdoor Use with ODS
The ROVSUN 18000 BTU heater stands out for its combination of power, portability, and long runtime, making it a top choice for backup heat in various settings. Its adjustable heat settings and 69-hour runtime on a 20-lb tank provide flexibility that surpasses many similar models like the Mr. Heater Big Buddy, especially in terms of operational duration. The all-metal construction and safety protections add peace of mind, though it demands proper ventilation due to venting requirements. Compared to ventless options, this heater requires more setup but offers greater control over airflow and safety. Its mobility, with locking casters, makes it ideal for garages, workshops, or outdoor use where frequent repositioning is needed. The tradeoff involves handling propane safely and ensuring adequate ventilation, which might complicate installation for some users.
Pros:- Powerful 18,000 BTU output suitable for up to 450 sq. ft.
- Long runtime of up to 69 hours on a single tank
- Battery-free piezo ignition for quick, reliable startup
- Portable with locking casters for easy movement
Cons:- Requires ventilation openings for safe operation
- Heats up to 450 sq. ft., less suitable for larger areas
- Propane handling and storage precautions are necessary
Best for: Homeowners or small business operators needing reliable backup heat with long runtime and portability
Not ideal for: Small indoor spaces or environments with strict ventilation constraints where ventless models excel
- Model:RS-HCG
- Fuel Type:Propane (LP Gas)
- Max Heating Output:18,000 BTU/Hr
- Heat Settings:3 (Low / Medium / High)
- Runtime on 20-lb Cylinder:69h / 35h / 23h
- Combustion Efficiency:98%
- Certifications:SGS Certified, CSA Standards
Our verdict“This heater is best for users needing a robust, portable backup heat source that can run long hours with good safety measures in place.”
Mr. Heater Big Buddy PRO Series Heater
The Mr. Heater Big Buddy PRO offers a substantial 18,000 BTU output with multiple heat settings, making it well-suited for indoor or outdoor areas up to 450 sq. ft. Its design is bulkier and heavier than portable models like the ROVSUN, but it compensates with a more robust build and adjustable heat modes, including safety features like tip-over protection and low-oxygen shutoff. Unlike the ventless Mr. Heater 30,000 BTU models, this heater requires external venting and careful setup, but it is better suited for continuous use in larger, well-ventilated spaces. Its multiple safety features provide confidence for prolonged backup heating, though its size and weight make mobility less convenient. This option is ideal for users who prioritize power and safety over portability.
Pros:- High 18,000 BTU output for sizable spaces
- Multiple heat settings and safety features for reliable operation
- Can connect to propane tanks for extended use
- Suitable for indoor and outdoor use
Cons:- Heavier and less portable than compact heaters
- Requires external venting and proper setup
- No electric or alternative power options
Best for: Home or business owners needing a powerful, reliable heater for larger, ventilated spaces
Not ideal for: Users seeking a lightweight, easily movable heater for small or poorly ventilated areas
- Heating Coverage:450 sq ft
- BTU:18,000
- Fuel Type:Propane
- Heating Method:Radiant and convection
- Item Dimensions:18.5″D x 18″W x 11.4″H
- Item Weight:14.1 pounds
- Number of Speeds:3
- Max Temperature:900°F
Our verdict“This heater is best for users needing substantial heating capacity and safety in larger, well-ventilated spaces, accepting less portability.”
ProCom Liquid Propane Ventless Ice House Heater – 10,000 BTU, Thermostat Control
The ProCom Ventless Ice House Heater delivers 10,000 BTU suited for small spaces up to 300 sq. ft., with safety features like an oxygen depletion sensor and thermostat control. Its ventless design simplifies setup, especially in outdoor shacks or ice houses, but it offers less power than larger models like the Mr. Heater 30,000 BTU, making it less ideal for larger greenhouse backup needs. The inclusion of a 10-foot hose and regulator makes it straightforward to connect to a standard propane cylinder, yet its limited heating capacity restricts use in bigger or poorly insulated spaces. Compared to vented heaters, this model sacrifices some safety and control for ease of installation and compactness, which might suit specific outdoor or emergency scenarios better.
Pros:- Safe with oxygen depletion sensor and auto shut-off
- Vented design eliminates need for chimney or ducting
- Includes long hose and regulator for easy setup
- Efficient 99.9% combustion efficiency
Cons:- Limited to 300 sq. ft., not suitable for larger greenhouses
- Requires a 20lb propane tank, still needs handling precautions
- Primarily designed for outdoor or ice house use
Best for: Campers, hunters, or small-scale outdoor spaces requiring safe, ventless heat
Not ideal for: Larger greenhouses or spaces needing more than 300 sq. ft. of coverage
- Technology:10,000 BTU Liquid Propane
- Safety Features:Oxygen Depletion Sensor, auto shut-off
- Heating Area:Up to 300 sq ft
- Fuel Type:Propane
- Includes:10-foot hose with regulator
- Dimensions:7″D x 14″W x 19″H
- Weight:15 pounds
- Max Temperature:100°C
Our verdict“This heater excels for small outdoor or ice house applications where ventless operation and safety are priorities, but it falls short for larger greenhouse backup needs.”
Mr. Heater 30,000 BTU Vent-Free Radiant Propane Heater
The Mr. Heater 30,000 BTU Vent-Free Radiant Heater delivers ample heat for spaces up to 1,000 sq. ft., making it a strong candidate for backup heating in sizable greenhouses or workshops. Its vent-free design simplifies installation, and features like a built-in thermostat and electronic ignition enhance usability. Unlike vented models, it requires no chimney or external venting, but this can increase indoor humidity and necessitate proper space sizing for safety. While it doesn’t include a blower, the direct radiant heat provides comfort, especially when power outages occur since it needs no electricity. Its lower altitude restriction (under 4,500 ft) limits use in mountainous locations, but for regular low-altitude sites, it offers reliable warmth.
Pros:- Heats up to 1,000 sq. ft. with 30,000 BTU
- No electrical power needed, ideal for outages
- Vent-free design simplifies setup
- Built-in thermostat and electronic ignition
Cons:- Not suitable for use above 4,500 ft altitude
- Blower fan kit sold separately
- Can increase indoor humidity and safety considerations
Best for: Large indoor spaces needing a powerful, easy-to-install backup heat source during outages
Not ideal for: High-altitude locations or spaces requiring forced-air circulation with a blower
- Heat Output:30,000 BTU/hr
- Heating Coverage:750-1,000 sq ft
- Fuel Type:Propane
- Ignition:Battery-operated electronic
- Thermostat:Built-in adjustable
- Dimensions:23.75″D x 11.25″W x 27″H
- Weight:26.3 lbs
- Max Temperature Setting:90 °F
Our verdict“This heater is suited for large, well-ventilated indoor backup heating, especially where power outages are frequent, accepting some humidity tradeoffs.”
Mr. Heater 30,000 BTU Vent-Free Blue Flame Dual Fuel Heater
The Mr. Heater 30,000 BTU Blue Flame Dual Fuel offers versatile operation on propane or natural gas, making it highly adaptable for backup heat in diverse settings. Its vent-free design and 1,000 sq. ft. coverage ensure straightforward installation and reliable warmth, comparable to the ventless single-fuel models but with added fuel flexibility. The built-in thermostat and electronic spark ignition improve control, though it requires careful setup to ensure safety, especially with dual fuel options. It’s primarily designed for indoor use, with no blower included, making it less suitable for large or poorly ventilated spaces where forced air might be preferred. The dual fuel capability makes it more adaptable in scenarios where natural gas supply is available, but handling two fuel types increases complexity.
Pros:- Heats up to 1,000 sq. ft. with 30,000 BTU
- Dual fuel capability for propane or natural gas
- No electricity required, electronic ignition included
- Adjustable thermostat and safety features
Cons:- Blower fan kit sold separately
- Floor-mounting feet not included
- Designed exclusively for indoor use
Best for: Indoor spaces with access to natural gas or propane, needing flexible backup heat options
Not ideal for: Outdoor use or spaces without natural gas connections, due to ventless design and fuel dependency
- Heat Output:30,000 BTU/hr
- Heating Coverage:1,000 sq ft
- Fuel Type:Propane, Natural Gas
- Ignition:Electronic spark
- Thermostat:Built-in adjustable
- Dimensions:11.42″ D x 27.36″ W x 25.51″ H
- Weight:26.1 lbs
- Max Temperature Setting:90 °F
Our verdict“This heater offers excellent fuel flexibility for indoor backup heating in spaces with natural gas access, accepting the added setup complexity.”
MOZODAWN 2-in-1 Propane Heater & Stove, 13000 BTU Portable Outdoor Heater for Camping, Tent, Ice Fishing, Garage
This 2-in-1 unit from MOZODAWN stands out for combining both heating and cooking in a single portable design, making it ideal for outdoor activities where versatility is key. Compared with the Mr. Heater 9,000 BTU Portable Buddy, it offers higher heat output and the convenience of cooking, which can be a real advantage in colder conditions. However, its dual functions come with tradeoffs: it is bulkier and requires a separate propane tank (not included), unlike dedicated space heaters that are more streamlined and easier to set up. The safety features—tip-over, flame-out, and low-oxygen shutoff—add peace of mind but do not compensate for the need to handle fuel tanks carefully. This pick makes the most sense for campers, ice anglers, or outdoor enthusiasts who want both warmth and meal prep capability in one device.
Pros:- Dual function as both heater and stove for cooking and warmth
- Triple safety protection with tip-over, flame-out, and low-oxygen shutoff
- Fast 360-degree radiant heating up to 13,000 BTU
- Portable design with handle and included hose connector
Cons:- Propane gas tank not included, requiring an additional purchase
- Not suitable for indoor or greenhouse use due to safety and venting concerns
- Bulkier compared to single-function heaters, less ideal for compact spaces
Best for: Adventure seekers and outdoor enthusiasts needing a combined heating and cooking solution in remote locations.
Not ideal for: Homeowners seeking a dedicated backup heater for stable indoor or greenhouse heating, as this is primarily designed for outdoor use and portability.
- Heat Output:13,000 BTU
- Heating Type:360-degree radiant
- Interface:Stainless steel threaded
- Included:5FT gas hose connector, instruction manual
- Gas Tank:Not included
- Safety Features:Tip-over switch, flame-out auto shutoff, low-oxygen shutoff
Our verdict“This heater-stove combo is best suited for outdoor users who need flexible heating and cooking, not for greenhouse backup heat.”
How We Picked
These heaters were selected based on their performance in providing reliable backup heat, safety features, ease of use, and fuel efficiency. We prioritized models with sufficient BTU ratings to cover typical greenhouse sizes and considered portability for emergency scenarios. Durability, safety certifications, and user reviews also played a role in our rankings. The products are ordered to reflect a balance between power, safety, and value, ensuring options for different needs and budgets. Our evaluation aimed to identify heaters that perform well in backup situations, where dependability and safety are paramount.| propane greenhouse heater for backup heat | Fuel type |
|---|---|
| Mr. Heater 80,000 BTU Convecti | Propane |
| Mr. Heater 9,000 BTU Portable | Propane |
| Propane Heater Indoor and Outd | Propane |
| Portable Propane Forced Air He | Propane |
| ProCom Heating Liquid Propane | Propane |
| ROVSUN 18000 BTU Portable Prop | Propane (LP Gas) |
| Mr. Heater Big Buddy PRO Serie | Propane |
| ProCom Liquid Propane Ventless | Propane |
| Mr. Heater 30,000 BTU Vent-Fre | Propane |
| Mr. Heater 30,000 BTU Vent-Fre | Propane, Natural Gas |
| MOZODAWN 2-in-1 Propane Heater | — |
