A greenhouse heater can help to preserve a warm outdoor environment for your plants over the colder months.
There are generally three different types of greenhouse heater to choose from these days – electric, gas and paraffin. Heat pumps and other more eco and energy-saving alternatives are being developed but these remain excessively expensive for your average gardener to invest in.
In terms of the current ‘big 3’, electric heaters have replaced paraffin as the most popular heaters amongst gardeners. They aren’t as dangerous as paraffin heaters (which are notoriously easy to knock over) and are easy to switch on and off. In addition, it’s really not necessary with an electric heater to have to regularly ventilate the greenhouse (as you would with a gas or paraffin version). Paraffin heaters release toxic substances and it’s essential that where they are positioned there is also access to an outside air source. That being said, electric heaters are undoubtedly the most expensive of the three to run.
Last update on 2021-04-22 / All Pricing & Imagery from Amazon Product Advertising API
If you are currently in the market for a garden heater then we hope the following guide helps. We have carried out a comparison of some of the most widely used greenhouse heaters in the UK. Specifically, we judged products on heat capacity, price, ease of use and source materials. Why not read through before you go out and buy something that really isn’t suited for your greenhouse and gardening needs?
A top-quality electric greenhouse heater which can also be used as a fan for air circulation.
Cost: Price not available
Our best heater is the Biogreen 2.8/GB. A quality item, with a powerful heat output of up to 2.8Kw, this is a heater that’s definitely meant for the keener and more serious gardener. That’s because it is capable of providing enough warm air for a greenhouse measuring up to 100 sq ft. In terms of frost protection, you won’t have any problems with dampness using this, even in a greenhouse of up to 180 sq ft.
This heater is excellent for the cultivation of young plants in a greenhouse because it’s powerful enough to provide a continuous and balanced heat during the winter months. This is partly down to a precision thermostat which delivers temperatures of between 0 and 26 centigrade. There are actually three heat output levels: 1.0 kW, 1.8 kW or 2.8 kW.
The Biogreen 2.8/GB is a good-looking, robust heater with a stainless-steel finish. Choose whether to hang it out of the way using the chains already supplied with the unit or, if you prefer, have it securely floor mounted on feet (also included).
Use the Biogreen 2.8/GB as a thermostatic heater or a fan-controlled version (which can also be used on its own), depending on your need and the time of year.
If you want a heater that doesn’t let you down – even during the freezing cold winter months – then you’ve found it.
- Quiet when running
- Very flexible, thanks to a choice of three different heat options
- Has both heating and cooling switch
- Rust-proof (ie spray waterproof)
- Energy-saving thermostat technology
- Robust so can stand a lot of moving around
- Isn’t particularly expensive to run
- Razor-sharp edges round the stainless-steel body at each end
- Most expensive of the heaters we assessed
A heater which doesn’t cost the earth to buy or run and is guaranteed to keep plants frost-free
Cost: Price not available
Our value pick greenhouse warmer is the Biogreen WM-P4 Paraffin Heater. Inexpensive and with low running costs compared to other forms of heating, it is capable of heating a greenhouse measuring around 8ft x 6ft. Four litres of paraffin can last in a greenhouse this size for as long as seven days.
There is a little more maintenance involved with this heater compared to other forms, mainly due to the wicks. These have to be trimmed and the flame coaxed to the correct size. Failure to get the right length of wick can result in your greenhouse being filled with soot. As a result, this heater may be better for someone used to handling paraffin heaters; otherwise electric might be better. If you still prefer paraffin and are new to greenhouse heaters then have a practice cutting the wicks and adjusting the flame height outdoors for a couple of days until you get the hang of it.
Having said that, if you’re looking for a heater which doesn’t cost the earth to buy or run and is reasonably easy to assemble, then the Biogreen WM-P4 Paraffin Heater is just the ticket. Your frost-free plants will definitely thank you for it.
- Easy to put together and use
- Attractive traditional design
- Energy-saving because it uses paraffin rather than electricity
- Not expensive to buy
- Works best with fresh paraffin
- Problems fitting the burner top screw into the black collar screw in some models
- Soot can result if the wick isn’t trimmed to the correct size
An excellent compact heater for small greenhouses where space can prove an issue
In terms of quality, the Biogreen 2.0/GB Heater & Digital Thermostat takes a lot of beating. Certainly, its temperature setting accuracy is legendary. It already has an internal thermostat (set to temperatures in the range of -50C to + 99C) but it works more efficiently when used in conjunction with the external thermostat – both can be purchased together to save money.
If not buying the external thermostat then you’ll find that the fan will continue to run once the heater reaches its desired temperature and automatically switches off. Having said that, there shouldn’t be any fear of over-heating since the heater itself slopes upwards, allowing cold air in and preventing the front mesh area becoming too hot. By continuing to run during winter your plants will benefit, but your pocket won’t, since it’ll bump up your utility bill.
In terms of maximum temperature raising ability, it’s possible for the Biogreen 2.0/GB Heater & Digital Thermostat to raise the temperature by three degrees in a standard 6X8 greenhouse in just a few minutes. It’s overall heating output being 2000 W and with an air circulation rate of 163 m3/h. Heating is achieved via two rings, rather than the standard wire coils.
Floor-standing, portable and splash-proof, this heater measures 280 mm length by 195 mm width by 315 mm height. A good quality heater and powerful heater that is reliable as well as efficient.
- Very economic to run
- Well-built and sturdy (built mostly using stainless steel)
- Doesn’t take up a lot of room in your greenhouse
- Slip-resistant rubber feet and comes with an easy-carrying handle
- IPX4 protection
- Use as an emergency heater in the home
- Fan continues to run after the heater is switched off which results in higher running costs
A basic heater that is easy to set up and does exactly ‘what it says on the tin’
This is a heater which works well in both small and larger greenhouses, as well as a conservatory in the home, the Large Paraseen Electric Greenhouse offers you a choice of two heat settings – 1000W or 2000W. The heating comes on instantly and can be adjusted very easily by using a dial.
Despite its name, this greenhouse heater isn’t particularly large – measuring just 19.5cm (L) 18cm (W) x 29cm (H). This means it doesn’t actually take up a lot of room in your greenhouse – leaving more space for cultivating seedlings – and is also easy to move around from one side of the greenhouse to the other (especially since it comes equipped with a handle on top).
This heater also offers a fan option, meaning you can forget about it producing any smells, such as humidity fumes etc.
- Robust and well put-together
- Neat and compact in terms of design
- IP24 Approved
- Painted green so it blends into the background
- The fan doesn’t switch off after heating reaches the desired temperature, and runs as soon as the heater itself is switched on
- Lead isn’t particularly long
A good paraffin heater in a traditional design which easily heats up your average-sized greenhouse
Cost: Price not available
Capable of heating a greenhouse measuring 12ft x8ft, the Biogreen WM-P5 Paraffin Heater produces an average temperature of 50 – 55 degrees.
The traditional design means there are no naked flames with the four burners and not all have to be used at once; it’s possible to light only two at a time. The wicks are one foot long each, meaning an increased 40 percent more burning time. The paraffin tank has a maximum 4.5-litre capacity (16 hours of burning) meaning you’re not going to be running back and forward to the garage for supplies too often – unless it’s a particularly cold spell.
Unlike many paraffin heaters, the Biogreen WM-P5 sits low on the ground so is easy for a cat, dog or child to accidentally knock over. Increased stability can be gained by using the fixing brackets which come supplied with the heater.
- Made with quality materials – even the filler cap is made from brass
- Has two wicks for each burner
- Comes with snuffers to put out each of the flames
- Easy to use
- Saves energy
- Not affected if there’s a power cut
- Supplied wicks are thin – but can be replaced with a thicker version for easy lighting
- No pre-drilled holes to fit the funnel – you’ll have to drill your own
- Instructions aren’t great – even with pictures to assist
- Not always easy to keep temperature constantly at the same level
How to Use A Greenhouse Heater
Electric greenhouse heaters remain very popular but – like paraffin and gas heaters – it’s important to keep them away from anything that’s likely to go up in flames. And if you have an extension cord running from the house, then regularly check the connections. Another essential is to ensure the heat moves around; this will ensure all the plants benefit from the heat and that condensation doesn’t take hold.
Another benefit of electric heaters is that if they come with a thermostat or automatic timer then these will switch themselves on and off while you’re at work. And you don’t have to worry about your heater becoming too warm and over-heating, thanks to automatic shut-off mechanisms.
Taking advantage of new digital greenhouse heater technology means that you’re approaching your gardening project with the savvy of a real horticulturist.
In order to benefit from your greenhouse heater, your greenhouse should be as well insulated as possible. That means ensuring there are no gaps between the windows and door where the cold can creep in. Many people use bubble wrap to seal gaps, but this can prevent any sunlight from getting into the plants. Covering plants with fleece can also help during particularly freezing spells.
A minimum temperature of 3ºC (37ºF) is usually all that’s needed to keep most plants flourishing. However, 7ºC (45ºF), and 10ºC (50ºF) is usually recommended for better protection (tomatoes, in particular, flourish best at 7ºC ). You can, of course, improve your chances of benefitting from ‘natural heat’ by positioning your greenhouse perfectly in the first place – ideally with its north wall against the side of your house facing south. That way you won’t require your electric as often and will cut back on running costs.
You could also create thermal mass by filling black containers with water then adding black food dye and placing them around the greenhouse. They should absorb heat in direct sunlight.
Another trick is to keep compost in the greenhouse; it’ll warm up the environment.
I'm an avid gardener and home DIY enthusiast from Yorkshire in the North of England. I'm passionate about helping our readers get out into their gardens - by making the most of the outdoors and ensuring they get the best possible deals on their gardening equipment. I also believe strongly in the preservation of our beautiful garden wildlife.