Greenhouse Heating Cost Calculator

How Much Does It Cost to Heat a Greenhouse?

The short answer: anywhere from about 50 pounds to over 500 pounds a year, depending on four things -- how big your greenhouse is, what it is glazed with, how warm you want it, and what fuel you use. I have heated greenhouses for over a decade now, and the single biggest factor is glazing type. Switching from single glass to twin-wall polycarbonate nearly halves your bill overnight.

Here are some realistic 2026 UK figures for a standard 6x8 ft (1.8m x 2.4m) freestanding greenhouse kept frost-free (above 2 degrees C) through the heating season (October to April):

These figures assume UK average electricity at 24.5p/kWh and natural gas at 6.2p/kWh (April 2026 Ofgem price cap). Your actual costs will vary depending on your tariff, your local climate (Scotland is roughly 1-2 degrees C colder on average than southern England), and how draughty your greenhouse is.

Use the calculator above to get a precise estimate tailored to your exact setup. Once you know your heating costs, you may want to check our frost date calculator to see when your last frost is likely and plan your heating season accordingly.

Greenhouse Heating Costs by Glazing Type

The glazing material is the biggest single factor in your heating bill because it determines how fast heat escapes. The measure we use is the U-value -- the lower the number, the better the insulation. Here is how the four common greenhouse glazing materials compare.

Single glass is still the most common glazing on UK greenhouses, especially the classic aluminium-framed models from manufacturers like Halls and Elite. It lets in the most light (around 90% transmission) but is the second-worst insulator on the list. Only polyethylene film is worse.

Twin-wall polycarbonate is the best all-round choice for heated greenhouses. It cuts heat loss by roughly 42% compared to single glass, is virtually unbreakable, and still transmits about 80% of available light. The small reduction in light is irrelevant during the winter months when you are heating. I replaced the single glass on my own 8x6 ft greenhouse with 4mm polycarbonate panels three years ago and my winter electricity bill dropped from around 230 pounds to 140 pounds -- it paid for itself in under two seasons.

Double glass offers the best insulation but is expensive, heavy and only available on premium greenhouse models. Unless you are building new and budget is not a concern, polycarbonate is the better investment.

Types of Greenhouse Heaters

I have used every type of greenhouse heater over the years, and each has genuine advantages depending on your situation. Here is an honest comparison of what is available in the UK right now.

Electric Fan Heaters

This is what I recommend for most gardeners. A thermostat-controlled fan heater like the Bio Green Phoenix gives you precise temperature control, circulates air (which reduces fungal problems like botrytis and damping off), and requires zero maintenance beyond occasionally wiping dust off the grille. The running cost is the highest of any option at 24.5p per kWh, but the thermostat means it only fires when needed. In a well-insulated polycarbonate greenhouse, a 2kW fan heater keeping frost-free might only run 4-6 hours per day in the coldest month.

Electric Tube Heaters

Tube heaters (also called tubular heaters) provide gentle, even background heat. They are quieter than fans and good for greenhouses where you want constant low-level warmth rather than on-off blasts. The downside is they do not circulate air, so you may still need a small fan running separately. I use tube heaters in my propagation area where consistent temperature matters more than rapid response.

Paraffin Heaters

If your greenhouse has no electricity supply, paraffin is your main option. The Parasene Super Warm range has been a UK greenhouse staple for decades. They burn cleanly and produce CO2 that plants use. The big drawback is no thermostat -- they burn at a fixed rate until the fuel runs out. This means you waste fuel on mild nights and risk under-heating on very cold ones. They also produce water vapour, which raises humidity and can encourage grey mould. I would always choose electric if power is available, but for an allotment greenhouse with no mains, paraffin works.

Gas Heaters

Natural gas is by far the cheapest fuel per kWh at just 6.2p -- roughly a quarter of electricity. If your greenhouse is close to your house and you can run a gas supply to it, the installation cost (typically 300 to 800 pounds for a short run) pays back within 2-3 years on a heated greenhouse. Propane bottled gas is a middle-ground option at around 10-15p per kWh equivalent, cheaper than electric but more hassle than mains gas due to bottle changes. Both gas types need adequate ventilation as they consume oxygen and produce CO2 and moisture.

How to Reduce Greenhouse Heating Costs

Before you spend money on fuel, spend a little on insulation. The cheapest heat is the heat you do not lose in the first place. I have personally tested all of these methods and they genuinely work.

Bubble Wrap Insulation

Horticultural bubble wrap with large bubbles (not standard packaging material) is the single best investment you can make. Fix it to the inside of your glazing with clips or tape. Large-bubble wrap reduces heat loss by 30-50% on single-glazed greenhouses, effectively giving you polycarbonate-level insulation at a fraction of the cost. A 50-metre roll costs 15-25 pounds and covers a typical 6x8 ft greenhouse. Replace it every 2-3 seasons as UV light degrades the plastic. The only downside is a 10-15% reduction in light transmission, which is a non-issue in winter.

Thermal Screens

A thermal screen or fleece curtain draped across the greenhouse at gutter height creates a false ceiling that traps warm air around your plants. This can reduce the heated volume by 30-40%, cutting costs proportionally. I use a sheet of horticultural fleece clipped to the glazing bars -- it costs about 10 pounds and takes 20 minutes to install. Remove it during the day to let light in, then drop it back at dusk.

Thermal Mass (Heat Sinks)

Water stores heat far better than air. Place black-painted water containers (old 25-litre drums, large plastic bottles) along the north wall of your greenhouse. During the day, they absorb solar heat. At night, they release it slowly, providing 2-4 degrees of free frost protection. In my lean-to greenhouse, six 25-litre containers along the back wall keep the temperature 3 degrees above outside on clear nights without any heater. It is not enough on its own in a hard frost, but it significantly reduces the hours your heater needs to run.

Draught Proofing

Gaps around doors, vents and where panes overlap leak more heat than most people realise. Seal gaps with self-adhesive foam tape (available from any hardware shop for about 3 pounds a roll). Check the base where the frame meets the foundation wall -- this is a common cold bridge. A strip of closed-cell foam or even old carpet along the base makes a noticeable difference. On aluminium greenhouses, replace any missing or perished glazing clips -- each missing clip creates a gap that whistles cold air directly onto your plants.

Only Heat What You Need

If you only need to protect a few trays of seedlings or a handful of tender plants, do not heat the entire greenhouse. A heated propagator (15-30 watts) or a small section partitioned off with bubble wrap costs a fraction of heating the full volume. I partition my 8x6 ft greenhouse in winter so I am only heating a 4x6 ft section. This alone cuts my heating bill by roughly 40%.

What Temperature Should a Greenhouse Be in Winter?

This depends entirely on what you are growing. Every step up in temperature roughly doubles your heating bill, so it pays to be honest about what you actually need rather than keeping things warmer than necessary.

In my experience, frost-free is the sweet spot for 90% of UK gardeners. It protects everything that needs protecting without breaking the bank. If you are growing winter salads (which I recommend -- nothing beats fresh lettuce in January), cool at 7 degrees C is worth the extra cost. Anything above that is specialist territory and you should be confident in the value of what you are growing before committing to those energy bills.

UK Greenhouse Heating Season

In most of the UK, the greenhouse heating season runs from October to April -- roughly 7 months. But the costs are not spread evenly. January and February account for 35-40% of your total annual bill because the temperature lift is greatest and the nights are longest.

The calculation is based on average UK monthly outside temperatures. When the outside average is below your target, you need heat. The difference between your target and the outside temperature is called the "temperature lift" -- the bigger the lift, the more energy you burn.

Note that the "average" hides a lot of variation. January averages 4 degrees C across the UK, but individual nights regularly drop to minus 2 to minus 5 degrees C. Your heater needs to cope with these extremes, not just the average. This is why I always recommend a heater rated 20% above your calculated peak heat loss -- the coldest nights are when it matters most.

Interested in when frosts will hit your area? Our frost date calculator gives local first and last frost predictions, and our planting calendar shows you exactly when to start seeds under heat.

Frequently Asked Questions

Best Greenhouse Heaters UK 2026

I have tested and researched the most popular greenhouse heaters on sale in the UK right now. These are my top picks based on performance, reliability and value for money.

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