3 / 5

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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.

4 / 5

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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.”

5 / 5

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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.

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.

Why You Should Trust Us

With more than 30 years working in the building trades, I used my hands-on experience and first-hand knowledge to select the best greenhouse heaters on the market. I’ve contributed to constructing a city in the Oregon desert, co-established two landscaping companies and worked as a carpenter, plumber and furniture refinisher. Since 2010, I’ve been sharing my expertise through DIY articles and serving as an online consultant, including with Home Depot’s Pro Referral service. My practical insights have been published on platforms like Landlordology, Apartments.com and Hunker, establishing me as a trusted source for reliable home improvement advice.

We consulted Sarah Boyce and Lori Johnson to gain more insight on why greenhouse heaters are needed and what factors you need to consider before buying one. Boyce is a franchise owner of Aire Serv of Bel Air, a Neighborly company. They’re experts on heating and cooling spaces. Johnson is the President of The Grounds Guys, a Neighborly company. They are licensed professionals who specialize in creating and maintaining beautiful lawns.

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.

FAQ

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 requiring proper ventilation.

What is the safest 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 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.

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