While there are many ways to heat a greenhouse for the winter (or for specialty tropical plants), using a heater is one of the most reliable methods. However, not all heaters are usable in a greenhouse; some can’t handle the humidity. To make it easier for homeowners, we’ve searched far and wide for the best greenhouse heaters available and then ranked them based on heat output, cost, and safety features.
Read these reviews to find the best greenhouse heater to keep your plants nice and toasty during cold weather. We’ve also included a buyer’s guide to help you figure out what features to look for when picking out a greenhouse heater.
Our top picks
Best electric greenhouse heaters – Reviews
Electric greenhouse heaters are among the safest and most reliable heaters for your greenhouse, but they often have a cord and need to be plugged into a power source.
1. PELONIS PHTA1ABB Portable Space Heater
The 5,118 BTU/hr of the PELONIS PHTA1ABB Portable Space Heater can heat up to 160 sq. ft., perfect for a greenhouse on the smaller side. Aside from having a low and high heat toggle, it also has an adjustable thermostat for precise temperature control. This convection heater also has a fan for good air circulation and spreading the warm air around evenly.
Fast and safe heating. This heater uses positive temperature coefficient (PTC) technology, specifically ceramic heater components. This makes it quickly heat up while still being energy-efficient. You don’t have to worry about overheating, as the PELONIS PHTA1ABB Portable Space Heater features overheating protection and a tip-over switch.
Useful all year round. The PELONIS PHTA1ABB Portable Space Heater also has a fan-only setting so you can use it even in the summer months to keep good air circulation for your plants. You can use it outside of your greenhouse, too; with its built-in carry handle and lightweight build, you can move it easily.
Product details
- BTU: 5,118
- Watts: 1,500
- Coverage: 160 sq. ft.
- Heating method: Forced air and convection
- Safety features:
- Automatic overheating shut-off
- Tip-over safety switch
- Made of flame-resistant ABS plastic
- Warranty: 1 year
Pros and cons
| What we liked | What we didn’t like |
| ✓ Precise temperature control ✓ Heats up fast ✓ Quiet ✓ Forced-air heating ✓ Has safety features ✓ Has a remote control ✓ Multi-functional and usable all year round ✓ UL-listed and ETL-compliant ✓ Easy to move ✓ Affordable ✓ Has a warranty | ✗ Fan is connected to the thermostat ✗ No timer ✗ Remote doesn’t always work |
Where to buy
2. Comfort Zone CZ220 Ceiling Mount Heater
Homeowners who want something more powerful will find the Comfort Zone CZ220 Ceiling Mount Heater more up their alley. It can output a maximum of 17,065 BTU per hour and can heat up to 750 sq. ft. of space, which is more than enough for even a large greenhouse. This heater has a dual-knob thermostat that lets you get the temperature right.
Precise heating. Just like other heaters on this list, the Comfort Zone CZ220 Ceiling Mount Heater is a forced-air unit. However, its louvers let you direct the unit exactly where airflow is needed the most. You can even adjust the angle of the heater itself for even more control.
Space saver. Because this heater is ceiling-mounted, homeowners won’t have to worry about giving up floor space to heat their greenhouses. However, this does mean that they can’t exactly move the heater easily, as they could a floor heater.
Product details
- BTU: 17,065
- Watts: 5,000 (max)
- Coverage: 750 sq. ft.
- Heating method: Forced air
- Safety features:
- Automatic overheating shut-off
- Power indicator light
- Warranty: 1 year
Pros and cons
| What we liked | What we didn’t like |
| ✓ Powerful ✓ Precise temperature control ✓ Forced-air heating ✓ Has safety features ✓ Adjustable ✓ Made of durable materials ✓ UL-listed and ETL-compliant ✓ Has a warranty | ✗ Fan is connected to the thermostat ✗ Fan needs to be reassembled when you get it ✗ Fan isn’t very strong and can fail |
Where to buy
3. PELONIS Oil-Filled Radiator Heater
Unlike the other PELONIS heater on this list, the PELONIS Oil-Filled Radiator Heater is a radiant heater. It doesn’t circulate hot air; instead, it heats objects in its immediate surroundings. Radiant heating is silent and doesn’t mess with your humidity levels, which is good if you need to maintain a certain moisture level in your greenhouse environment.
Easy to use. Homeowners can easily set the PELONIS Oil-Filled Radiator Heater to their desired temperature using the LED display and digital thermostat. You can also use the remote control that comes with the heater if you’re busy tending to plants on the other end of the greenhouse. You can set up a timer for up to 10 hours, too.
Heat on wheels. Despite it being on the larger side, this heater isn’t that difficult to move around because of the four wheels at its base and the handle up front.
Product details
- BTU: 5,120
- Watts: 1,500
- Coverage: 164 sq. ft.
- Heating method: Radiant (static)
- Safety features:
- Automatic overheating shut-off
- Power indicator light
- Tip-over safety switch
- Timer
- Warranty: 1 year
Pros and cons
| What we liked | What we didn’t like |
| ✓ Precise temperature control ✓ Quiet ✓ Has safety features ✓ Has a remote control ✓ Easy to move ✓ UL-listed and ETL-compliant ✓ Has a warranty | ✗ Heat setting resets when you unplug it ✗ Reverts to low power mode when you use the timer ✗ Has a smell, especially when on high |
Where to buy
4. Dr. Infrared Heater DR-975 Electric Heater
Just like the Comfort Zone CZ220 Ceiling Mount Heater, the Dr. Infrared Heater DR-975 Electric Heater is a powerful ceiling-mounted model. It also has louvers you can use to direct airflow. However, this 7,500-watt heater is much more powerful, outputting nearly 26,000 BTUs per hour.
Temperature options. The Dr. Infrared Heater DR-975 Electric Heater comes with a remote-controlled built-in thermostat that allows homeowners to set their greenhouses’ temperature from 50°F to 85°F. You can also hardwire this heater to an external wall-mounted thermostat if you prefer that.
Hardwired. Unlike the other corded heaters we’ve listed, the Dr. Infrared Heater DR-975 Electric Heater is hardwired. Thus, it doesn’t come with its own cord. Instead, you’ll need to connect this heater to your house’s wiring with 8 AWG copper wires.
Product details
- BTU: 25,597
- Watts: 7,500
- Coverage: 750 sq. ft.
- Heating method: Forced air
- Safety features:
- Automatic overheating shut-off
- Timer
- Thermal-protected fan
- Warranty: 1 year
Pros and cons
| What we liked | What we didn’t like |
| ✓ Powerful ✓ Precise temperature control ✓ Quiet ✓ Forced-air heating ✓ Has safety features ✓ Adjustable ✓ Has a remote control ✓ UL and cUL-listed ✓ Has a warranty | ✗ Will shut off before the greenhouse reaches your desired temperature if it’s too close to a wall because of the internal thermostat ✗ Fan is too slow, which doesn’t help with the overheating ✗ Needs to be hardwired, so needs some technical knowledge to set up ✗ Will need to be turned back on after a power outage |
Where to buy
5. AirNmore Comfort Deluxe Infrared Space Heater
The AirNmore Comfort Deluxe Infrared Space Heater is another heater that uses PTC technology for efficient and long-lasting heat. However, it uses copper instead of the PELONIS PHTA1ABB Portable Space Heater‘s ceramic. The copper elements of this heater mean you can kiss replacing heater bulbs goodbye.
Pet and child safe. The AirNmore Comfort Deluxe Infrared Space Heater stays cool to the touch thanks to its dual high-temperature limit sensors. It also has a sensor that shuts the unit off when tipped over. So, you won’t have to worry about the little ones burning themselves if they want to explore and help around your greenhouse.
Smart heater. This heater has auto-reboot memory, meaning it will remember what heat settings it had before a power outage.
Product details
- BTU: 5,000
- Watts: 1,500 (max)
- Coverage: 1,000 sq. ft.
- Heating method: Forced air
- Safety features:
- Dual overheating sensors
- Tip-over sensor
- Warranty: 2 years
Pros and cons
| What we liked | What we didn’t like |
| ✓ Energy-efficient ✓ Cool to the touch ✓ Remembers settings even after a power outage ✓ Forced air heating ✓ Has safety features ✓ Has a remote control ✓ Easy to move ✓ ETL-listed ✓ Has a warranty | ✗ Much more expensive than other units with similar heating output ✗ Noisy ✗ Fan could be of better quality, especially for its price |
Where to buy
Best gas-powered greenhouse heaters – Reviews
Gas-powered heaters can run on either propane or natural gas. In general, they are less energy-efficient and eco-friendly than electric heaters, but they don’t need to be plugged in.
1. Mr. Heater Big Buddy Portable Propane Heater
With a max heat output of 18,000 BTUs per hour, the Mr. Heater Big Buddy Portable Propane Heater is a good option for homeowners looking for a reliable gas-powered greenhouse heater. This heater can heat up to 450 square feet, which is more than enough for most greenhouses.
Safe heating. While they don’t need wires and cables, gas-powered heaters have some downsides; mainly, the fact that they use up oxygen in the air. The Mr. Heater Big Buddy Portable Propane Heater has an oxygen depletion sensor that shuts off the unit when it detects a low amount of oxygen in the air. This heater also has a tip-over safety switch.
Easy to set up. Its swivel-out fuel connectors allow you to easily hook up two 1 lb. propane cylinders to your heater. If you need even more fuel, you can buy additional Buddy accessories that let you connect it to a 20 lb. propane tank.
Product details
- BTU: 18,000 (max)
- Fuel capacity: 1 lb. propane cylinder (x2), can use a 20 lb. propane tank with accessories
- Coverage: 450 sq. ft.
- Heating method: Radiant
- Safety features:
- Oxygen depletion sensor and automatic shut-off
- Tip-over safety switch
- Warranty: 1 year
Pros and cons
| What we liked | What we didn’t like |
| ✓ Powerful ✓ Adjustable heat settings ✓ Has safety features ✓ Can be connected to a larger fuel source ✓ CSA-certified ✓ Portable | ✗ Smells ✗ Only runs up to 3 hours on max heat unless hooked up to a 20 lb. tank ✗ Attachment hose comes separately ✗ Doesn’t come with a carbon monoxide detector |
Where to buy
2. Mr. Heater F232000 MH9BX Buddy Portable Propane Heater
Don’t need the power of the Big Buddy heater? Mr. Heater’s F232000 MH9BX Buddy Portable Propane Heater is the Big Buddy’s smaller, less powerful sibling. Outputting a maximum of 9,000 BTUs per hour, this greenhouse heater can heat up to 225 square feet of space.
Big Buddy, but smaller. Since it’s just a smaller version of Mr. Heater’s Big Buddy model, the Buddy Portable Heater has the same features. It shuts off when it detects low oxygen levels and has tip-over protection.
Only one cylinder. The Mr. Heater F232000 MH9BX Buddy Portable Propane Heater can only take one 1 lb. propane cylinder of fuel unless you buy the hose accessory. With the hose, you can hook it up to a propane tank.
Product details
- BTU: 9,000 (max)
- Fuel capacity: 1 lb. propane cylinder, can use a 20 lb. propane tank with accessories
- Coverage: 225 sq. ft.
- Heating method: Radiant
- Safety features:
- Oxygen depletion sensor and automatic shut-off
- Tip-over safety switch
- Automatic overheating shut-off
- Warranty: 1 year
Pros and cons
| What we liked | What we didn’t like |
| ✓ Adjustable heat settings ✓ Heats up fast ✓ Has safety features ✓ Can be connected to a larger fuel source ✓ CSA-certified ✓ Portable | ✗ Only runs up to 3 hours on max heat unless hooked up to a 20 lb. tank ✗ Attachment hose comes separately ✗ Doesn’t come with a carbon monoxide detector |
Where to buy
3. Dyna-Glo 30,000 BTU Natural Gas Heater
Natural gas is usually a cheaper fuel source than propane. If you would rather have a powerful greenhouse heater powered by natural gas, then consider the Dyna-Glo 30,000 BTU Natural Gas Heater. Heating up to 1,000 sq. ft. of space, this wall-mounted heater doesn’t require venting through a flue or chimney.
Blue flame technology. The Dyna-Glo 30,000 BTU Natural Gas Heater’s blue flame isn’t just for show. Blue flame heating technology heats air much more cleanly than orange or yellow flames, so there’s no soot. It heats up greenhouses and other spaces through convection, circulating warm air all throughout.
Oxygen sensor. This heater has a built-in oxygen depletion sensor that shuts the unit off not only when there’s a lack of oxygen but also when there’s a build-up of carbon monoxide. However, it doesn’t have a thermostat or an overheating protection system.
Product details
- BTU: 30,000
- Fuel capacity: Hooked up to your natural gas line
- Coverage: 1,000 sq. ft.
- Heating method: Radiant
- Safety features:
- Oxygen depletion sensor and automatic shut-off
- Warranty: 1 year
Pros and cons
| What we liked | What we didn’t like |
| ✓ Powerful ✓ Heats up quickly ✓ Will run as long as it’s properly connected to your natural gas line ✓ Easy to install ✓ Has an oxygen depletion sensor | ✗ Not available in some states ✗ Might be too powerful for smaller greenhouses ✗ No thermostat control (thermostat model is more expensive) |
Where to buy
Buyer’s guide to greenhouse heaters
Are you looking to buy a heater for your greenhouse? Here are the things to look out for so you can buy the right greenhouse heater for your needs.
Heat output and coverage
The main factor to look out for is how powerful a heater is. More powerful heaters can raise an area’s temperature by a fair bit, and they can also heat larger greenhouses with ease. While it’s best to check how large of an area a heater can affect – usually in the description of a heater – looking at the heat output is not a bad way to determine if a heater will be good for your greenhouse.
Heat output is typically measured in British Thermal Units (BTUs). A larger BTU rating means more power.
Just make sure you’re buying a heater with a heat output that matches your greenhouse’s heating needs. More powerful heaters might not be able to go below a certain BTU rating, making your small greenhouse too hot.
Fuel source
Another major factor to consider is a heater’s fuel source. There are many ways to power a greenhouse heater – wood, electricity, natural gas, propane, kerosene, and even solar panels – and each one has its pros and cons. Let’s talk about electricity and gas as fuel sources, the only fuel sources we’ve included in this list.
Electric heaters are cleaner, typically more precise, and sometimes cheaper to power compared to gas heaters. Electric heaters don’t use up oxygen and don’t produce carbon monoxide, which can be deadly in large amounts. However, they’re largely corded; they need to be plugged in and will fail during a power outage.
Gas heaters run on either propane or natural gas. Natural gas is cheaper, but not as clean nor energy-efficient as propane. Propane is more environmentally friendly than natural gas.
Precise temperature control
Since temperature is quite important for growing plants, you’ll want a heater that you can fine-tune for the perfect greenhouse environment. Not all heaters have thermostats that can help you set the precise temperature your heater should heat your greenhouse to.
Some heaters don’t even have more than two to three heat settings. If you don’t have a thermometer in your greenhouse, you might want to invest in one if you choose a heater without precise temperature control.
Safety features and certifications
Since they output heat – sometimes needing a flame – heaters have the potential to be quite dangerous. For the maximum safety, look for a heater with automatic shut-off systems. They can trigger when the heater is tipped, starts overheating, or when it detects low oxygen or high carbon monoxide levels.
Some heaters also come with certifications, such as the Underwriters Laboratories (UL and cUL) mark, Electrical Testing Laboratories (ETL) mark, and the Canadian Standards Association (CSA) mark. The UL, cUL, and ETL are marks that say an electrical device has passed standards, while CSA is used for other products – not just heaters.
Upfront cost
Some heaters are quite expensive because of the extra bells and whistles that they come with. Others become more expensive because of renovations. You might need to renovate if you didn’t build your greenhouse to take temperature control into account.
Keep in mind that cost doesn’t just mean the cost of the heater unit. There are long-term costs of running a heater, mainly fuel and maintenance. Some fuel sources, like electricity and natural gas, are cheaper than others; wood can be cheap as well if you end up with a lot of wood over the winter.
Cost of keeping a greenhouse warm
The greenhouse heaters on our list range from a little over $30 to more than $250, but that’s only for the heater itself. Expect your heating costs to rise over time due to fuel and maintenance costs. You may even need to buy multiple heaters depending on the size of your greenhouse.
However, that’s not the only way to keep a greenhouse warm. Insulating your greenhouse or using construction materials with high R-values can help keep your greenhouse toasty throughout winter even without a heater. The cost of greenhouse insulation ranges from $1.50 to $4 per square foot.
Learn more about the cost of building and maintaining a greenhouse in our complete guide to greenhouse costs.
FAQ about greenhouse heaters
1. How can you keep your greenhouse warm cheaply?
Keeping your greenhouse warm doesn’t have to be expensive. Some cheap ways to warm a greenhouse are using fall leaves as insulation and adding materials with high thermal mass. You can even make a tiny DIY heater. Learn more in our article about how to heat a greenhouse.
One of the best ways to keep greenhouse heating costs down is to insulate your greenhouse or use one of the insulated greenhouses from our list of the best greenhouse kits. That way, your greenhouse will experience less heat loss.
2. How many BTUs do you need to warm your greenhouse?
There are many ways to calculate how many BTUs you’ll need to warm a greenhouse. One way is by multiplying your greenhouse’s total square feet by its U-factor (dependent on materials) and then multiplying that value by heat loss (70 is the maximum amount of heat loss).
A much simpler formula is multiplying your greenhouse’s area by 77. This will give you a rough estimate of how much BTU you will need to heat your greenhouse.
It might be better just to look at a heater’s coverage area if you want to save yourself the headache of calculating BTUs.
3. What temperature should you heat your greenhouse to in winter?
You should warm your greenhouse to a minimum of 37° Fahrenheit to support even the most tender plants. Ideally, your greenhouse should be 45°F to 50°F for your garden to thrive in the winter.
Let pros get your garden ready for winter
Heating isn’t the only thing homeowners need to take care of to get their greenhouse gardens ready for the winter, and it’s not like every homeowner can dedicate the time and energy toward their gardens this fall. Hiring a professional gardener can free up your time without leaving your flowers and ornamentals to fend for themselves. Get a free quote from a local gardening pro through Lawn Love today.
Main Photo Credit: Sanga Park / Canva Pro / License
