Best Heater for Small Greenhouse: Which of These 5 Models Wins?

If you’re looking for the best heater for small greenhouse temperature control, you’ll find it here in this comprehensive review of five products.

We’ll share everything we found out about the pros and cons of each of these five small space heaters so you can choose the one that matches your needs.

At the end of this review, we’ll also tell you which one we chose as the winner in five product feature categories: largest heating area, most compact, most lightweight, best temperature control, and overall best heater for greenhouses.

All of the products in this review are electric greenhouse heaters designed for heating small spaces and working in conditions around growing plants, so read on to discover which electric small greenhouse heater is the one you need to keep your plants thriving. 

Quick Product Comparison Chart

Best 5 Heaters for Small Greenhouse

–Dr. Heater Small Greenhouse Space Heater

• Compact size, portable and light
• Convenient handle on top
• One temperature setting 
• Water splash protective design 

This Dr. Heater model uses infrared heat to warm up nearby objects while other heaters in this review produce radiant heat that warms the air in the space being heated. By contrast, infrared heat does not warm the air in the area between the heater and whatever is near it. Instead, it produces a form of heat that is not felt until it touches whatever objects are nearby in the room. 

– Heat Setting and Output

The Dr. Heater DR218 has a single heat setting of 1500 watts at 12.5 amps for producing a warm and cozy environment in up to 150 square feet on even the coldest days. It plugs into a standard 120-volt outlet and starts heating seconds after turning it on.

The motor contains heavy-duty components for reliable performance and is factory sealed and lubricated, so you never need to worry about maintaining it. 

This heater also contains a heat sensor for precision temperature control and prevention of overheating, and it shuts off if the unit gets too hot due to a built-in thermal fuse. The fan is also heavy-duty and built to last for many years if the unit is used according to the manufacturer’s instructions. 

– Splash-Proof Housing

This heater is advantageous for use in a small greenhouse space because it is designed with the IPX4 housing that protects the electronics inside from water splashing. Nonetheless, this is an electrical device that must not be submerged in water or allowed to get seriously wet, or it could produce a safety hazard. 

– Easily Portable

The Dr. Heater product has an easy-to-grip metal handle on top that makes it highly portable and straightforward to move around wherever you need it. The handle material wraps around the front of the unit to prevent the hot grill from contacting the floor or other surfaces if the heater tips over.

– Downsides

The manufacturer states that this heater is reliable to ambient temperatures of 50º F, and when the outside air cools off below this point, the heater might not work correctly.

Using this heater in an enclosed greenhouse on cool nights is likely to work well to protect tender plants and keep them growing. However, if your location has extremely low temperatures, this product might not be a good choice. 

In addition, some buyers have reported that the unit overheats and poses a fire hazard. However, this problem might be due to users plugging the heater into an extension cord. It’s crucial to understand that this electric heater should not be used with an extension cord, or it could damage the fuse and heating element and void the warranty. 

– AgiiMan Small Greenhouse Heater with Thermostat

• Adjustable thermostat
• 5118 BTU
• Convection forced air 
• 89 inch long cord 
• Safe around children and pets 

The AgiiMan Outdoor Patio Heater is a highly portable electric heater using convection forced air to warm small spaces like greenhouses. One switch on top of the device controls the fan speed, and the other adjusts the temperature setting. In addition, a light lets you know if the unit is turned on. 

– Adjustable Thermostat and Forced Air Fan

This heater’s adjustable thermostat allows you to choose a heat setting range on the dial control. Once you turn it on, it starts working to heat the space in only three seconds, making it ideal for getting warm temperatures in minimal time. The three available settings are ‘natural wind,’ ‘warm wind,’ and ‘hot wind,’ and a single switch controls all. 

The heat generated inside the device is forced outward with a small fan, producing a blast of warm air that quickly circulates in the space, keeping your greenhouse plants from freezing on cold days and nights. When the device is set on the heating function, a safety feature will automatically shut off if the temperature exceeds a safe limit. 

– Extra-Long Cord

This heater has the longest electric cord of all the products in this review. The extra-long cord makes it easy to plug in this model and move it around in a small area without needing to change to another outlet to reach where you want to place it, which is a significant advantage in many greenhouses.

– Fan Only Setting 

Another advantage of this heater is that you can use it on the ‘fan only’ setting for circulating air without added heat. You can operate the fan on either a high or low setting to adjust the breeze to match the exact needs of your greenhouse plants.

On cool nights where light frosts are possible, a simple fan device like this can protect tender greenhouse plants without skyrocketing the electric bill for unneeded heating. 

– Keep Pipes from Freezing

Many greenhouses have water pipes that can freeze in cold weather, leading to a disaster for plants and expensive and time-consuming repairs. This heater can also come in handy for keeping a warm breeze blowing over pipes and faucets to prevent freezing, keeping the vital watering system in your greenhouse functioning in winter. 

– Downsides

This unit is small, and some buyers complain that it is too small to heat anything but a tiny area directly in front of the heater. In addition, some buyers report that the fan appears to be unbalanced, causing the heater to vibrate and move around when the fan is set on the high setting.

There are also reports of the control knob becoming stuck after a few weeks or months of use, and the manufacturer states the product should not be used in damp conditions that occur in a greenhouse. 

– OPOLAR Portable Greenhouse Heater

• Ceramic heater
• Adjustable thermostat
• Over-heating protection
• Fast heating 
• 1,000 and 1,500-watt settings 
• Heating and fan only settings 

The OPOLAR is a digital, ceramic space heater that lets you choose the temperature setting from two options of 1000 watts for lower heat ranges and 1500 watts settings for maximum warmth.

Ceramic heaters like this have a long-lasting core of dense ceramic inside that heats up from the electric current and then radiates that warmth into the surrounding environment. This design has no open electric coils that can create a safety hazard or burnout. It comes in two colors, black, and silver. 

– Large Fan for Hot or Cool Air 

This OPOLAR space heater has a built-in electric fan for blasting out warmth and heating up to 400 square feet of indoor space in a greenhouse. The ceramic heating element gets hot quickly, so you can expect a cozy warm area in about three seconds after turning on the device. The thermostat automatically turns the heater on and off, depending on the ambient temperature and the heat setting you select. 

The unit has two digital controls. One changes the setting between high, low, and fan only, and the other sets the fan speed. So if you only want to blow air without heat, you can use this heater on a fan-only setting, which can also come in handy for keeping greenhouse environments at an even temperature for growing plants. 

– Compact and Lightweight

This heater is also exceptionally compact and light, making it convenient to move around or store away when you don’t need it.

The sleek design and shape make this heater attractive and practical. In addition, the rugged top handle is extra-convenient for moving the device and carrying it to new locations. 

– Safety Features 

If the heater accidentally gets tipped over on any side, it has a safety feature that instantly shuts it off to prevent a fire or electrical hazard. The heater also has a built-in overheating sensor to automatically shut off if it gets too hot. If this heater reaches a hazardously high temperature above 149º F, it automatically shuts off for safety. 

– Low Noise Levels

In addition, this heater is exceptionally quiet at approximately 50 dB when it’s running on the high setting, which is a beneficial feature in noise-sensitive environments. 

– Downsides

One downside of this heater, when used in a greenhouse, is that it does not oscillate, so the warm air only comes out directly in front of the device.

The other downside is that this is a popular space heater, and it can be hard to find.

– MULTIFUN Mini Greenhouse Heater

• Convection forced air
• Adjustable thermostat 
• Tip-over protection 
• Heating and fan only settings 
• Easy carry handle on top 

This Multifun electric heater is the most miniature model in this review, measuring only 7 by 6.7 by 6 inches in size and weighing only 2.4 pounds. If you have an extra-small greenhouse or a cold frame you want to warm up, this model is tiny enough to fit in a tight space easily. The minute size, low weight, and rugged top handle make it easy to move this heater around anywhere you need it. 

– Forced Air and Ceramic Heating Element

The Multifun heater uses forced air from a ceramic element and a small fan to generate warm airflow that keeps plants comfortable when the weather gets chilly and prevents freezing in a small space. In addition, the device’s exterior is constructed with UL and ETL certified flame-retardant plastic, which makes it safe against a fire hazard.

In addition, an overheat protector and a tip-over protection switch keep shut down this device if it gets too hot or falls over. Finally, the ceramic element is durable and won’t burn out from regular use, providing you with a reliable heat source for many seasons. 

– Fast Warming and Precise Temperature Control 

This electric heater warms up in seconds and generates up to 1500 watts of output on the high setting, letting you rapidly warm a space up to 108 square feet in minutes. The thermostat adjusts using a dial that keeps the ambient temperature between 41º – 95º F, a comfortable and safe range for warming plants in a greenhouse. 

– Large Heating Area Distribution

One unique feature of this heater is the angled shape of the unit that directs heat upward rather than blasting it out straight in front of the heater. This design helps distribute the warm air over a larger area and warm a bigger space. 

– Low Noise Levels

This heater is ultra-quiet with a sound rating of 50 dB, and it also does not have any lights visible on the front, making it inconspicuous and less annoying at night. 

– Money-Back Guarantee

This device comes with a 90-day money-back guarantee, so you can quickly return it if it does not prove to suit your needs. It also has a one-year warranty. 

– Downsides

One downside of this unit is the length of the cable at 4.9 feet long.

This length is short for use in many locations, and the manufacturer does not recommend using an extension cord, so this could be a problem in a greenhouse.  

– PELONIS Small Heaters for Greenhouse Spaces

• Vortex heater and fan
• 90º adjustable tilting stand
• Convection heater 
• 900 and 1500 watt settings 
• Overheating and tip-over shut off protection 

The PELONIS portable heater with a vortex fan is ultra-compact with a round housing that tilts up to 90º inside the frame so you can adjust the angle of the heat flow exactly where you want it to go. The sturdy metal base keeps this fan upright and stationary.

Still, if it does tip over accidentally, a switch inside the device senses the movement and instantly shuts off the power to prevent a fire hazard. 

– Ceramic Heating Element

This PELONIS heater uses a ceramic core for rapid and sustained heating without exposing a hot heating element coil or open flames. The powerful but subtle heat source is ideal for warming cold greenhouses and other small spaces.

The temperature settings are visible on an easy-to-read digital display rather than a dial. Choose from two high and low settings for the optimum heating level for your environment and heating up to 175 square feet of space. 

– Adjustable Digital Settings 

It has two heat settings on a digital control panel with the low-temperature setting at 900 watts and the high one at 1500 watts, allowing you to choose a temperature range suitable to your needs. It also has a fan-only mode, so you can also use it on warm days to circulate air and keep the environment pleasantly breezy.

– Adjustable Housing

Compared to others in this review, one of the unique features of this device is that the heating unit tilts inside the sturdy frame that supports the unit. This feature allows you to rapidly adjust airflow direction from downward to straight-ahead to upward.

This adjustability can be exceptionally useful for warming the environment without blasting hot air directly onto tender plants in a greenhouse situation. 

– Compact Size and Low Weight

This heater measures 11.9 inches high, 7.6 inches wide, and 11.1 inches deep and weighs 4.36 pounds, making it highly portable and easy to move around.  

– Warranty

This space heater comes with a one-year manufacturer warranty. 

– Downsides

One of the few downsides of this heater is that the area it can warm is relatively tiny.

The manufacturer recommends it for heating only up to 175 square feet of space. 

Product Comparison

The main differences between these electric greenhouse heaters and small greenhouse heaters are in the types of heating elements they use, how much space they can warm, whether or not they have adjustable temperature settings, and how light and portable they are. Now, we will compare these five heaters side-by-side in five feature categories and choose a winner for each. 

– Largest Heating Area

Winner: OPOLAR Ceramic Space Heater

The OPOLAR has the largest capacity for heating of all of the heaters reviewed here. It is capable of warming a space up to 400 square feet. However, it’s essential to keep in mind that the height of the room you are heating is crucial in how large an area the heater can warm. For example, rooms with low ceilings warm up faster than rooms with high ceilings. 

– Most Adjustable

Winner: PELONIS 

Like the OPOLAR, AGIIMAN, and MULTIFUN heaters, the PELONIS has two wattage settings and an adjustable thermostat for precision temperature control. However, only the PELONIS allows you to change airflow direction by tilting the heating unit inside the frame, making it the winner for this category. 

– Most Lightweight

Winner: MULTIFUN 

If you want the lightest possible space heater for your greenhouse, the MULTIFUN space heater wins at only 2.6 pounds.

– Most Compact

Winner: MULTIFUN

The MULTIFUN heater is also the smallest, measuring only 7 inches high by 6.7 inches wide and 6 inches deep. However, this heater also has the smallest heating area at only 108 square feet, so the slight warming capacity offsets the ultra-compact size. 

– Overall Best Heater

Winners: OPOLAR and PELONIS

Our top picks for the best heaters for small greenhouse spaces are the OPOLAR and the PELONIS heaters. These heaters have adjustable settings and precision temperature control along with a fan-only setting that is most useful in a small greenhouse.

In addition, they can heat more extensive areas than the other heaters, matching the size of many small greenhouse spaces. 

Additional Safety Information about These Heaters

Like the ones reviewed here, electric heaters can be a significant asset in your greenhouse to keep plants from freezing during cold weather.

However, it’s crucial to use these products following the manufacturer’s instruction manual and follow basic safety rules for the protection of people, pets and structures, including:

• Do not touch any part of the heater grill surface with bare skin when the device is on.
• Only use the heater outside if the manufacturer states it is safe.
• Do not place anything on top of or near the heater. 
• Prevent the heater from getting wet, and do not use it near bathtubs, swimming pools or other open bodies of water 

Conclusion

Electric heaters do not produce the same indoor air quality concerns as combustion heaters like those using propane as a fuel, making them useful in greenhouses.

However, electric space heaters like the ones reviewed here are more expensive to operate than combustion heaters, and they can pose safety hazards if misused. Therefore, the buyer should always read and closely follow usage instructions in the owner’s manual. 

The best heater for small greenhouse temperature control depends partly on the size of your greenhouse and how cold the ambient air is inside the unheated space. Each of these heaters can be useful in some situations. However, in our opinion, the OPOLAR and PELONIS heaters are the most versatile and adjustable electric heaters for use in a small greenhouse.