You've given your plants shelter from the winter by building a greenhouse. Now you need a greenhouse heater to take away the chill.
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A greenhouse shields seeds and plants from the elements while maintaining a warm environment. However, even a well-insulated greenhouse may require assistance when the temperature drops. Buying a greenhouse heater provides the additional warmth plants need.
“Factors that can determine if a heater is needed are climate, location and the species of plant,” says Sarah Boyce, franchise owner of Aire Serv of Bel Air, a heating and air conditioning company.
It’s important to choose wisely: Oversize the heater and your plants will bake, while undersizing it may result in paying for gas or electricity without the benefits.
“Plants that would not normally grow due to cold weather can thrive in a greenhouse using a heater. The heater in the greenhouse can also allow for year-round growing,” says Lori Johnson, President of The Grounds Guys, a landscaping and lawn care service. “Plant roots grow better in warm conditions. The warm conditions help with root growth and plant resiliency. A heater in a greenhouse can be used to temporarily store potted plants when frost is expected.”
Unless you’re growing tropical plants, your greenhouse heater doesn’t need to maintain the same temperature as your home. Nonetheless, setting a target temperature based on your specific crops is essential. This determination will guide you in selecting the appropriate type of heater and the required heat output. Keep reading for the best options on the market.
What to Look for When Buying a Greenhouse Heater
What is the best type of heater for a greenhouse?
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On Sale
Best Overall Greenhouse Heater
Bio Green Palma Greenhouse Heater
Pros:
- Sturdy stainless steel casing
- Compact size and lightweight
- Easy-to-use adjustable thermostat
- Energy-efficient
- Powerful heating output
Cons:
- Not suitable for spaces larger than 120 square feet
Designed for small greenhouses, the Bio Green Palma Greenhouse Heater puts out 5,200 BTU, enough to heat 120 square feet. This electric space heater has a built-in circulation fan and draws 1,500 watts of electricity on a 120-volt circuit. Lightweight and sturdy, this splash-proof unit features an auto-shutoff in case of overheating.
A detachable 0 to 90-degree thermostat can be removed from the heater housing and mounted at eye level. It also earns top marks from Amazon raters and reviewers, with many customers noting how easy it is to use. Another happy shopper, Dswift13, calls it the “best greenhouse heater ever” adding, “I’m so glad we found these heaters! Definitely worth the money!”
Dimensions: 11 by 8 by 12.5 in. | Weight: 4.5 lbs. | Type: Electric
Best Budget Electric Greenhouse Heater
Dr. Heater DR218 Infrared Greenhouse Heater
Pros:
- Wallet-friendly
- Precision temperature sensor
- Built-in over-heat protection
- Adjustable thermostat control
- IPX4 structure protects against water splashing
- Heavy-duty steel housing
- Lightweight and portable
Cons:
- Warranty is for parts and repair only
The Dr. Heater DR218 Infrared Heater is equipped with a single 1,500-watt setting, an adjustable thermostat and a temperature sensor for efficient cycling on and off to maintain a consistent temperature. With the capacity to warm an area of up to 150 square feet, this straightforward heater also features a fan-only mode for warmer days, ensuring air circulation around delicate flora.
Its stainless steel housing offers a sturdy build, yet it’s still lightweight and extremely portable, making it easy to direct radiant heat precisely where it’s needed for greenhouse plants. Additionally, the heater includes an automatic shut-off function to prevent overheating, providing both convenience and safety.
Dimensions: 10 by 15 by 10 in. | Weight: 13 lbs. | Type: Electric
Best Large Electric Greenhouse Heater
Comfort Zone Ceiling-Mount Heater
Pros:
- Heats large spaces, up to 1,000 square feet
- Fan-forced design for wide heat dispersion
- Adjustable thermostat for precise temperature control
- Removable front grill for easy cleaning
- Adjustable louvers provide targeted airflow
- Overheat protection sensor
Cons:
- Not portable
Hardwiring into a 240-volt circuit is a requirement for the Comfort Zone Ceiling-Mount Heater, but it delivers an impressive 17,065 BTU of heating power while drawing 5,000 watts of electricity. This unit, similar to this Mr. Heater Garage heater, hangs from the ceiling, which frees up valuable floor space. Its powerful fan-forced design effectively disperses heat throughout a large area, while movable vents enable precise heat direction.
The adjustable thermostat control provides settings of 3,000, 4,000 and 5,000 watts, allowing you to get just the right temperature for your space. For added safety, the greenhouse heater includes a built-in sensor that automatically shuts off the unit in case of overheating, and an indicator light ensures you know exactly when it is powered on.
Dimensions: 17.25 by 13.7 by 14.5 in. | Type: Hard wired
Best Propane Greenhouse Heater
Mr. Heater F232000 Buddy Heater
Pros:
- Connects quickly to a one-pound propane bottle or a 20-pound tank
- Affordable
- Swivel out regulator for easy fuel connection
- Emergency low-oxygen safety system
- Accidental tip-over safety shut-off
- Includes Piezo igniter
Cons:
- May shut off at altitudes higher than 7,000 feet
The Mr. Heater F232000 Buddy Heater features two settings that deliver 4,000 and 9,000 BTU, providing coverage for up to five hours. The portable unit operates on a one-pound propane cylinder but can also connect directly to a 20-pound tank with the purchase of a hose and filter. Rated for indoor use, this heater doesn’t require ventilation, making it ideal for heating small spaces up to 225 square feet.
This popular pick boasts more than 21,000 five-star ratings on Amazon, including Quiltlady-1958 who calls it “fantastic,” enthusiastically writing: “We highly recommend this heater!!! It is safe, easy to use, and does the job!!! We like the size and weight.”
Another happy shopper, Ben, says “Love my little buddy,” and provides a helpful tip: “You can save a lot of money by refilling your one-pound tanks. It’s super cheap and easy to do with a propane refill adapter. I reuse one pound tanks over and over all winter long for pennies on the dollar.”
Dimensions: 14.25 by 8 by 15 in. | Type: Propane
On Sale
Best Greenhouse Radiator Heater
Pelonis Oil Filled Radiator Heater
Pros:
- Efficient and cost-effective electrical heating solution
- Four swivel wheels for easy mobility
- Auto shut-off protection
- Safety tip-over switch
- 10-hour timer and remote control
- Eco energy-saving mode
- Five temperature settings (65°F to 85°F)
Cons:
- Only for small spaces up to 164 square feet
Oil-filled radiator heaters are mostly used for warming up indoor spaces. However, they can provide enough ambient heat to protect plants from frost in a 120-square-foot greenhouse when temperatures drop below 32 degrees. The Pelonis Portable Space Heater features three power settings and uses electricity to heat its oil-filled radiator. It’s smart too, turning off when the oil is warm enough to spread the heat around, which saves energy. Unlike many oil heaters, this one has its own fan to keep warm air circulating throughout the space.
Dimensions: 14.17 by 11.02 by 25.2 in. | Weight: 17.64 lbs. | Type: Electric
On Sale
Best Heater for Small Greenhouses
Vornado Space Heater
Pros:
- Built-in timer
- Distributes heat evenly
- Compact build
- Comes with a remote control
Cons:
- Cannot get wet
What to Look for When Buying a Greenhouse Heater
- Size: To determine the BTU (British thermal units) size needed for your greenhouse, multiply its square footage by the desired temperature increase and an insulation factor. The insulation factor depends on how well-insulated your greenhouse is, with 1.0 for minimal and 1.5 for good insulation. The formula is BTUs = greenhouse square footage × temperature increase × insulation factor. A size calculator like the one at ACF Greenhouses can help with your calculations.
- Fuel source: If you want to use natural gas or electricity, your greenhouse must be equipped for it. Otherwise, your options are propane or paraffin. Paraffin isn’t as easy to find as it used to be, so paraffin heaters aren’t common.
- Ventilation: Some propane and natural gas heaters need good ventilation. Many burn so efficiently that ventilation isn’t an issue, although the small possibility of carbon monoxide off-gassing means you should install a carbon monoxide detector. Electric heaters have no emissions and don’t need ventilation.
- Static or forced-air: A static heater distributes heat by convection, which is fine for a small greenhouse. A large greenhouse in a cold climate may need a forced-air heater.
- Thermostat controls: A heater with a thermostat can self-adjust to maintain a steady temperature. If you make frequent trips to the greenhouse, you may not need this feature, but it’s nice to have.
- Safety features: Greenhouse heaters are sometimes left unattended for long periods, so most electric ones have a breaker that trips when the unit begins to overheat. Some gas heaters monitor oxygen levels and switch off when those levels fall too low. And most heaters, whether gas or electric, switch off automatically when they tip over.
- Splash protection: Many electric heaters are splash-proof, so they won’t be affected if you spray them while watering plants.
How We Found the Best Greenhouse Heaters
We researched lots of different greenhouse heating options, taking into account size, fuel source, efficiency and safety features. Then, we research the features that speak to the product’s quality, taking advice from industry insiders and subject matter experts on what makes a product a smart value (or worthy of a splurge). Finally, we do the work of combing through user reviews to see how real people interact with these heaters, and if they stand up to the test.
FAQs
What is the best type of heater for a greenhouse?
The best type of heater for a greenhouse depends on factors such as the size, climate and specific plant requirements. Electric fan heaters are efficient for smaller spaces, providing even heat distribution. Oil-filled radiators offer steady warmth without drying the air and are suitable for medium-sized greenhouses. Propane or gas heaters are effective for larger structures, delivering powerful heating, but they require proper ventilation.
What is the best source of heat for a greenhouse?
Electric heaters with built-in safety features are often considered the safest choice for greenhouse heating. They eliminate open flames, carbon monoxide emissions and the need for combustible fuels. Models with tip-over protection and overheating shut-off features enhance safety by automatically turning off the heater in case of accidental falls or excessive heating.
What temperature should you heat your greenhouse to in winter?
The ideal winter temperature for a greenhouse depends on the plants being cultivated, but a common recommendation is to maintain a minimum temperature of 45 to 50 degrees Fahrenheit during the night to prevent frost damage. “The general daytime range is between 70 to 80 degrees,” says Johnson. Some cold-tolerant plants may thrive in slightly cooler conditions, while more delicate or tropical varieties may require higher heat.
Do greenhouse heaters use a lot of electricity?
That depends on how often you run the greenhouse heater and what kind you have. Larger spaces require more heating to cover the area. In general, a propane heater is a more cost-effective option than an electric model.
Why Trust Us
I’ve spent more than 30 years working in the building trades. Constructing a city in the Oregon desert, co-establishing two landscaping companies and working as a carpenter, plumber and furniture refinisher are just a few highlights on my resume. My practical insights have been published on publications including Landlordology, Apartments.com and Hunker, establishing me as a trusted source for reliable home improvement advice.
I consulted Sarah Boyce, a franchise owner of Aire Serv of Bel Air, a Neighborly company, and Lori Johnson, president of The Grounds Guys, a Neighborly company, to gain more insight on why greenhouse heaters are needed and what factors you need to consider before buying one. They’re both licensed professionals in the heating and cooling space. Using her content strategy and SEO expertise, Caitlyn Fitzpatrick, an editor and writer since 2014, helped update this piece.
