Best greenhouse heaters for winter: Keep your plants warm and thriving

Cold weather can be a real issue for greenhouse producers. In winter, because it gets so cold, plants can suffer or even die, especially fragile seedlings and tropical species. The temperature inside a greenhouse can plummet to unhealthy levels without heating, causing growth to be stunted, frostbite damage on leaves and even complete crop loss.

Like an electric blanket, a heater is frequently necessary to protect and nurture plants throughout winter. A decent greenhouse heater can keep inside warm despite freezing temperatures outside. It insulates plants from the cold, and allows gardeners to grow crops year-round.

Types of Greenhouse Heaters

Various types of heaters are used to heat greenhouses in the winter. They work in different ways and are appropriate to different sizes and kinds of greenhouses.

1. Electric Heaters

Greenhouses often use electric heaters. And they’re a snap to use, without the need for fuel, but just power.

• Forced-Air Heaters: These heaters push warm air into the greenhouse. They warm up the area fast and are the most popular heaters for small to medium-sized greenhouses.
• Infrared (Radiant) Heaters: These heat objects and plants, not only the air. They are most effective in well-insulated greenhouses as they lose less heat.
• Oil-Filled Radiators and Fan Heaters: These heaters release heat slowly and uniformly over time. They are quiet, safe and can come with tip-over protection and automatic shut-off.

2. Propane Heaters

Propane heaters are built to get the gas from a propane tank. They are effective and practical if there’s no electricity in a greenhouse.

• Vent-Free and Vented Heaters: Vent-free heaters are easy to set up, but they do require excellent airflow for the air to remain safe to breathe. Vented heaters are safer and better for long term use, but harder to install.
• BTU Output and Fuel Use: Models such as the Mr. Heater F274805 and Dyna-Glo are powerful enough to heat medium to large greenhouses. They generate a lot of heat and can be cheaper to operate than electric heaters.

3. Natural Gas Heaters

Natural gas heaters are best for large or commercial greenhouses. They are connected to a gas line, so there’s no need to refill a tank.

• Modine Hot Dawg® Series: These units are designed for larger areas. They generate a great deal of heat and are designed to burn for a long period of time. They do require a fixed gas connection, but typically are more cost-effective to run than electric heaters in the long run.

4. Solar and Passive Heating

These are sun-powered heaters to heat the greenhouse. They help save money on the energy bills, but they may not be enough on nights when it’s very, very cold.

• Passive Solar Design: This include things such as bubble wrap on the walls of a greenhouse, or water/filed barrels (or rock) that hold onto heat during the day and release it at night time.
• Solar Electric Heaters: As the name suggests, this kind of heaters, use solar panels to generate electricity. Some have batteries to store power for use at night.

5. Geothermal and Ground-Source Heat

These systems utilize the natural warmth underground to heat the greenhouse. They are very energy efficient but expensive to install.

• Earth Tubes and Buried Systems: Tubes or systems are buried underground where the temperature remains constant throughout the year. Once in place, they require little energy to continue operating.

Key Considerations When Choosing a Heater

If users are purchasing a greenhouse heater, there are a number of important factors to consider. The appropriate heater will have the correct space size, energy usage, safety and degree of installation and maintenance ease. Here is what to look out for:

Greenhouse Size and Heating Capacity

The size of the greenhouse is a big factor in choosing the appropriate heater. Each of the heaters will have a heating capacity expressed in either BTU (British Thermal Units) or watts.

• Larger greenhouses require more powerful heaters to keep the air warm in colder weather.
• One general rule is to calculate the cubic feet of the greenhouse (length × width × height) and then match that to the heater’s BTU rating.
• For small greenhouses (up to 100 sq. ft.), a heater with 1,000–2,500 watts may be enough. Medium greenhouses could require 5,000–10,000 watts or more depending on the climate in which it is located.

Tip: Choose a heater that’s rated for the coldest temperatures experience in the area especially if the greenhouse is not well insulated.

Energy Efficiency and Operating Costs

Select a heater that is efficient with energy, especially if you plan to use it for several hours a day.

• Electric heaters are sterile and simple, but electricity can be expensive.
• Propane and natural gas heaters generally are less expensive to operate over time, but they require adequate ventilation and a steady supply of fuel.
• Some regions even provide energy rebates or price reductions for using environmentally friendly heaters, like solar powered systems.

Tip: Consider a heater with a thermostat or a timer. These mechanisms help save energy by switching the heater off once the desired temperature is reached.

Safety Features

Heaters in general need to be safe to use, particularly in rooms with water, plants and potential flammable materials.

• Overheat shutoff: Shuts down the heater if it overheats.
• Tip-over switch: Automatically turns off the heater if knocked over.
• Flame sensor: Discovers whether the flame is functioning properly, which is found in gas heaters.
• Safety certifications: Keep an eye out for labels such as UL (Underwriters Laboratories) or CSA (Canadian Standards Association). These indicate the product is up to safety standards.

Tip: Always follow the manufacturer’s safety instructions, and don’t leave a heater running unattended for extended periods.

Installation Requirements

There are plug-and-play safe heaters for greenhouses, and there are others that require a little more work to install.

• Best electric greenhouse heater usually only need a plug, but larger units may require a 220V outlet or special wiring.
• A gas and propane heater for greenhouse might require adequate venting, fuel line and clearances from walls or the ceiling.
• Ensure the heater is appropriate for the space and does not obstruct walkways or plants.

Tip: Look for small electric heaters; they are acceptable for beginners. For larger heaters, the user may require professional assistance to ensure safe and proper installation.

Maintenance and Longevity

The heater also requires maintenance to keep it functioning properly.

• Wash air filters to maintain strong airflow and reduce dust.
• Inspect fuel tanks for leaks and fill if necessary.
• Test thermostats to ensure the temperature remains constant.
• If maintained, safe heaters for greenhouses can last many years, though lower-cost models may wear out sooner.

Tip: Look for a heater that has a solid warranty and likely options for the more expensive or longer term models.

Best Greenhouse Heaters for Winter

The right heater can provide protection against the elements and ensure that the plants stay safe and warm during the colder months. Growcycle, for instance, is home to many quality and efficient greenhouse heaters. Here are some of the top heater picks:

1. Modine PTP300SS-0111 Tubular Natural Gas Heater

This natural gas heater has a high capacity and is great for large greenhouses or commercial spaces. It’s got a stainless-steel burner and a power-vented system to provide even and efficient heating. Its sturdy design means it will be a long-lasting investment for serious growers.

• Ideal for: Large commercial greenhouses
• Heating Power: 300,000 BTU/hour
• Fuel Type: Natural Gas
• Key features: High output, stainless-steel construction, efficient heating

2. Modine PTP250SS-0111 Tubular Natural Gas Heater

It's a good model for medium to large greenhouses. It has high heating performance through its high efficiency tubular heat exchanger. It’s quick to install and is ideal for locations where strong, energy-efficient greenhouse heating is required.

• Ideal for: Medium to large greenhouses
• Heating Power: 250,000 BTU/hour
• Fuel Type: Natural Gas
• Key features: Efficient design, easy installation, reliable operation

3. Modine Tubular Natural Gas Heater

This is a reliable small to medium greenhouse heater. It also uses a power-vented blower to ensure even heat distribution and safety. It also comes with a stainless steel burner and it is designed to endure long periods of usage throughout the winter time.

• Ideal for: Smaller greenhouses or areas needing steady heat
• Heating Power: 200,000 BTU/hour
• Fuel Type: Natural Gas
• Key features: Strong build, steady heating, easy venting

4. Titan Controls Ares Greenhouse Garden Heater

It's a combination system that heats the greenhouse and releases some CO₂ for the plants. It’s best for small greenhouses or indoor grow spaces. The unit includes oxygen-level monitoring, a tip-over safety switch and a built-in CO₂ controller. It’s the safe, intelligent, and efficient solution for year-round use.

• Ideal for: Small greenhouses or grow tents
• Heating Power: 35,000 BTU/hour
• Fuel Type: Natural Gas
• Bonus Feature: CO₂ Generation
• Key features: Built-in CO₂ controller, safety features, easy setup

Installation and Maintenance Tips

A greenhouse heater can be made to work safely and to last longer if it's installed correctly and maintained. Some things users can do will make a big difference, so whether it’s an electric, gas, or propane heater for greenhouse.

1. Choose the Right Location: Install the heater in a place where it can deliver equal heat to everywhere. And make sure it’s well away from flammable objects, vents and sources of water.
2. Mounting the Heater: Employ the brackets or assembly which comes with the apparatus. Wall or ceiling mounted units must be fixed to the solid structures using screws or expansion bolts.
3. Wiring (for electric heaters): Determine if there is adequate electrical capacity in the greenhouse. Wire according to the manufacturer’s diagram. Hire an electrician just in case people doubt electrical connections.
4. Venting (for gas and propane heaters): Vent the exhaust gases out of the building with an appropriate venting kit. Make sure that vents are securely closed and follow the clearances for the heater. For vent-free models, make sure to have great circulation in the greenhouse.
5. Setting the Thermostat: Wire the thermostat as directed in the installation manual. Keep it at plant height, out of direct heat. Turn the temperature to the desired setting, typically ranging from 45 degrees to 75 degrees, depending on the plants.

Safety Tip: Please read the product manual and comply with all local building codes. It is best left to professionals for gas lines or complicated installs .

Seasonal Maintenance Checklist

By making a few simple checks before, during and after winter, growers can protect their equipment from dying on them in the middle of a season and extend its life and reliability.

Pre-Winter Service (Before the First Cold Days)

• Clear the heater and its environment.
• Examine for corrosion, rust, or loose parts.
• Test the thermostat and safeguards.
• For gas models, examine the gas line for leaks.
• Clean filters and air inlets.

Mid-Season Inspections (Every 1–2 Months)

• Keep an ear and eye out for audible and olfactory abnormalities.
• Confirm the heater comes on and goes off properly.
• Inspect for obstructions in vents and filters.
• Fill propane tanks if necessary.

End-of-Season Shutdown

• Turn off and disconnect the power or fuel supply.
• From the heater inside and out.
• Protect cover or put it away under ready for use if removable.
• Identify any fixes that will need to be made before next winter.

Tips for Long-Term Use

• For the best electric greenhouse heater, use surge protectors.
• Maintain good ventilation and cleanliness in the greenhouse.
• Keep track of any problems or fixes in a maintenance log.
• Review the warranty to see repair choices.

Optimizing Greenhouse Temperature Management

Even in the cold months, nothing is more crucial to a well-functioning greenhouse than keeping it at the right temperature. The following is how to get the temperature management in the greenhouse operating effectively.

1. Integrating Thermostats, Timers, and Smart Controllers

The temperature is controlled by a thermostat, which automatically switches the heater on or off at a predetermined temperature. Growers can also save energy by setting temperatures at various levels throughout the day with a programmable thermostat.

Timers can be used to regulate when the heater comes on or off, making certain it is used only when required. This is particularly good for cutting out warmth at night or during those lighter evenings.

To fine-tune control, there are smart thermostats and controllers that can hook up to the smartphone or computer. Growers can use these systems to access and manage their greenhouses from anywhere. A small number of smart systems also enable connection with humidity and CO₂ sensors, and automatic fans, to provide complete control.

2. Using Vents, Fans, and Dampers for Even Heat Distribution

Opening and closing vents at the correct time will also control temperature by releasing the excess heat. Vents and automatic or adjustable openings can be set to open and close as temperature or humidity dictates.

Cooling air can be distributed throughout the greenhouse with the aid of fans. Exhaust fans expel hot air and circulation fans move air over plant beds, warding off cold pockets and establishing a consistent temperature.

Dampers are doors or valves that can be set to open or close to varying degrees to control the air flow through ducts, for accurate winter greenhouse temperature control. By incorporating dampers along with the vents, the heat will distribute more evenly, particularly in larger greenhouses.

3. Supplementary Heat Retention

User can hang thermal curtains inside the greenhouse which trap heat at night, making the inside temperature warmer. Curtains can be particularly effective at reducing the heating bills, providing an extra layer of insulation but without shading the room from daylight when the sun is shining.

Insulating walls, ceilings, or floors can cut heat loss. Options such as bubble wrap insulation, thermal blankets or double-glazed windows can make the greenhouse warmer and more efficient with less energy. Insulation also prevents drafts and controls the interior temperature.

FAQs

What is the most efficient heater for a greenhouse?

The natural gas Modine Tubular heaters are usually the most economical since it has the lowest operating cost and is capable of heating a lot of space.

How to heat a small greenhouse?

There is no best small greenhouse heater, but the way to heat the greenhouse effectively is by using a combination of energy-efficient heaters, insulated panels (so users can reduce the heating cost) and a ventilation system to regulate the temperature.

Will a greenhouse keep my plants warm?

Yes, the greenhouse absorbs heat from the sun and warms the interior, but additional heat may be needed in the extreme cold.

The Bottom Line

In winter, a warm greenhouse is critical to prevent plants from being frozen, while still providing enough light and moisture. The correct heater also keeps the interior warm and cozy even when it’s freezing outside. Alongside warmth, insulation and vents and fans is also key for temperature control.

The use of thermostats and timers serve to save energy and to maintain a consistent heat. The heater lasts longer and works more safely with regular maintenance. For impressive, energy-efficient greenhouse heating, visit Growcycle for the reliable products.

Disclaimer: This material is for informational purposes only and should not be relied on for legal, medical, financial, or any other form of professional advice.

About the Author

Victor Miller

Environmental Journalist Focused on Sustainable Agriculture

Victor Miller is an environmental journalist at Growcycle, specializing in sustainable agriculture. With a passion for storytelling, he highlights the latest trends, innovations, and practices that promote ecological balance and responsible farming.