The 6 Best Greenhouse Heaters For Winter Months
By Thomas O'Rourke - 27th October, 2018
Gardening becomes seriously challenging when temperatures drop. Whether you have a portable greenhouse, or you’ve invested in a more permanent solution, heating the space during winter is a must.
Luckily, UK retailers offer a bountiful range of greenhouse heaters, from small devices suitable for a propagation tent to large units for spaces of over 100 square feet.
Choosing the best greenhouse heater takes a lot of consideration though. From the size of the unit to the technology involved and energy efficiency, there are many factors to account for. That’s why we’ve tested and rated some of the most promising greenhouse heaters in the UK and picked our favourites. Check them out below.
In this guide - our best picks for greenhouse heating, including...
Best Of The Rest
A compact freestanding greenhouse heater capable of delivering unrivalled power output and air circulation rates.
The traditional twin chimney design lets you choose between fuel efficiency and maximum heat.
Electric fan heater ideal to use in a greenhouse or other space of up to 8×12 feet.
Two heat modes and cool air function make this electric heater an all-season essential.
The Bio Green Phoenix is an outstanding electric greenhouse heater designed to heat up to 100 square feet and offer frost protection in spaces up to 180 square feet. Constructed in high-quality rustproof steel, this unit offers two functioning modes and acts as a cooling fan or heater depending on the season.
The unit is easy to operate from two analogue knobs and boasts three heat output options which allow you to choose either maximum power at 2.8 kW or energy efficiency at 1 kW.
Ideal for heating greenhouses or the interior of your home, the Bio Green Phoenix provides consistent heat or ventilation and comes equipped with a precision thermostat, with variable temperature control between 0 and 26°C.
We also liked the multiple setup options. You can use this heater either as a freestanding or suspended unit, thanks to the floor feet and suspension chains included in the box.
Perfect for protecting your plants from frost or to promote propagation, Phoenix is no doubt one of the best units on the market.
Budget-savvy gardeners will probably appreciate this tube greenhouse heater. It comes not only with an attractive price but is one of the most energy efficient on the market.
Coming in three sizes which output from 45 to 135 watts, this tubular unit is ideal for smaller environments, although its efficiency largely depends on the size of the greenhouse and the outside temperatures.
On the bright side, the unit is easy to connect to a thermostat and can be programmed to switch on only during night time, for example.
Lacking a temperature control feature, the tube gets very hot when in function and it is recommended to install it at a distance from any flammable materials including tent fabric, plastics and plants.
Efficiency is offered by the radiant heat technology which transfers heat to the objects rather than the air, preventing the emergence of any hot spots as well as the heat dissipation. Furthermore, the product is splash-resistant and does a great job in protecting plants from frost.
The smaller brother of the Phoenix unit above, the Bio Green Palma is another product that doesn’t disappoint. If you have a smaller greenhouse and plants that require consistent heat, Palma could be your best bet.
This is a great floor-standing heater capable of outputting up to 2 kW of power. A reliable bimetal thermostat allows you to set any temperature between 0 and 85°C while the 190-centimetre cable enhances mobility.
Perfect for greenhouses, damper room, and garages, this electric unit boasts a rugged steel construction and is IPX4 splash-proof.
Two intuitive knobs allow you to control both the temperature and the heating mode as either static or ventilated; furthermore, it is even possible to use the unit for ventilation purposes only.
With the fan on, the product provides air circulation at a rate of 163 cubic metres per hour.
If you’re looking for an alternative to the popular electric units, the Bio Green WM-P5 Paraffin is a great unit to consider. Running on paraffin oil and boasting a traditional two chimney design, this unit promises to keep your plants in a warm environment throughout the winter.
Unsuitable to use in your home due to carbon dioxide emissions, this heater is perfect for the greenhouse for the same reason. The extra CO₂ will, in fact, help your plants thrive in the coldest months.
The 4.5-litre tank holds sufficient fuel for up to 16 hours of constant heat, while the temperature intensity is easy to control by lighting one or both burners. However, the unit doesn’t have a thermostat, and you must switch it off manually as needed.
A great advantage of this greenhouse heater is its simple maintenance. You will also be able to keep your plants in a suitable environment during power outages and will never have to worry about the impact greenhouse heating has on your electricity bill.
This 2kW Greenhouse Fan Heater is another great product to consider if you like the reliability of an electric unit. A dual operating mode makes the unit perfect to use both in the warm and cold seasons, in a space of up to 8×12 feet.
Compatible with a variety of thermostats, the heater ensures powerful temperature control even during the colder nights when temperatures hit -10°C or less.
Powerful and durable, the product boasts a power output of 2,000 watts and comes with a strong metal casing powder coated in an attractive green colour which camouflages the heater amongst plants.
We also like the stainless-steel heating element and the powerful fan which provide a constant and even temperature thanks to minimal heat dissipation and optimal airflow.
Reliable in most conditions, the unit performs wonderfully in larger greenhouses too if you only want to maintain a frost free environment and is compact enough to fit on a shelf.
Praised for its capabilities and exceptional price, the Botanico 2 kW Greenhouse is the last heater featured in our list, but not by its importance.
In fact, the product impresses with exceptional quality and, depending on your needs, is ideal to use in greenhouses up to 10×6 feet.
Two power modes allow you to choose from frost protection and energy efficiency or high heat while the cool air function ensures a proper airflow during any warmer days. The maximum power output is 2 kW, which is ideal for heating a greenhouse up to 6×6 feet.
Like most electric heaters, Botanico comes with an IPX4 safety rated housing which is splash-proof and ideal to use in humid environments.
Designed to keep your greenhouse above freezing point, whilst being affordable and reliable, this is one of the best greenhouse heaters you can find.
How To Heat A Greenhouse During Winter
A greenhouse provides cold weather protection to your warm weather plants, but keeping the temperatures above freezing point during the colder months could be challenging.
Although greenhouses are built to capture and store the heat coming from the sun, your plants will certainly welcome some auxiliary help when the temperatures drop below 0°C.
Luckily, keeping a greenhouse or conservatory warm during winter is less complicated than it seems. Here are a few tips from our experts to help make things easier:
- Learn how to position your greenhouse
Sun exposure plays an important role in keeping your greenhouse warm during the winter. When erecting the structure, position it in an east to west fashion along its length, so one full side will always be exposed to the south. Also, try to place the northern side as close as possible to a wall or fence.
This position exposes a larger part of the structure to the winter sun, while the other side is protected from wind, providing insulation.
- Insulate the greenhouse
It is useless to argue a greenhouse is made to provide frost protection. If you really care about your plants, add a further layer of insulation to your structure.
Plastic greenhouses benefit the most from sheet foam insulation during the night. Alternatively, clip bubble wrap to the interior of your greenhouse to minimise heat loss.
In a glass greenhouse you should insulate the northern wall with moisture-proof foam insulation.
- Create thermal mass
This fancy term describes those objects capable of absorbing heat during the day to then release it during the night.
The easiest way to create thermal mass in a greenhouse is with water containers. It is recommended to use black containers and also colour the water with black food dye to increase heat absorption.
Three-litre capped containers are the most commonly used; just fill as many as needed with water and place them throughout the greenhouse in areas exposed to direct sunlight.
- Store compost inside the greenhouse
Nothing makes your plants thrive in the warm season like good organic fertiliser.
Making compost and storing it in the middle of the greenhouse is a win-win situation. You’ll create optimal nutrients for your plants while the pile will warm up the environment during the cold winter.
Keeping the compost in the greenhouse also comes with other benefits as the pile won’t be exposed to rain, which could wash off some of the nutrients.
- Get a reliable greenhouse heating system
From electric fan heaters to paraffin oil systems or fuel-powered alternatives, the market is full of options to choose from.
Regardless of the system you buy, the key to keeping your greenhouse warm during winter is nailing the right temperature.
Temperate weather plants don’t require tropical temperatures during winter, so if you want to protect vegetables or native plants, it could be a waste of money investing in a system that releases high levels of heat.
Most vegetables and perennials are happy in temperatures just above freezing point. More sensitive plants, like tomatoes, may require a minimum temperature of 7°C, while very young plants and a few delicate species like the Sundaville may need over 13°C.
- Position the heater where it’s needed
If your greenhouse is rather small, place the heater centrally at one end of the greenhouse, paying attention to direct the airflow above any plants placed in the proximity of the heater.
In a larger greenhouse, it is advisable to group the most delicate plants in an area of the structure and direct the airflow towards that area.
Use bubble wrap to create further insulation between the sensitive plants and the rest of the greenhouse if needed.