By the UK Glasshouse Guide — Expert Reviews, Comparisons & Buying Advice Team · Updated May 2026 · Independent, reader-supported

How to Heat a Glasshouse in Winter UK: Best Methods Compared

Keeping your glasshouse warm enough through a British winter is one of the biggest challenges for growers, whether you're protecting tender perennials, forcing early vegetables, or maintaining a collection of exotic plants. Temperatures can plummet below freezing for weeks at a time, and a single hard frost at the wrong moment can wipe out months of work. The good news is that several proven heating methods exist, each with distinct advantages and trade-offs depending on your setup, budget, and what you're growing.

Why Heating Matters in UK Glasshouses

Most plants grown in UK glasshouses—from tomatoes and cucumbers to orchids and succulents—need protection from temperatures below 5°C. Unheated glasshouses can reach 0°C or lower on winter nights, even when the air outside is only slightly colder. The glass conducts heat away rapidly, and there's no mass inside to retain warmth overnight. Without heating, your options shrink dramatically, and you'll lose tender plants.

The goal isn't always to maintain summer warmth. Many growers aim for frost-free conditions (5–10°C), which is enough to keep most plants ticking over through winter without triggering growth. That's usually cheaper than heating to 15–20°C, which some fruit or vegetable crops need.

Electric Heaters: Reliable but Running Costs Matter

Electric fan heaters and convection heaters are the most straightforward option. They plug in, turn on when temperature drops, and deliver steady heat without mess or fumes. Most come with built-in thermostats that cycle on and off to maintain your target temperature.

Pros: No fuel to store or buy in bulk. No combustion, so no ventilation risk. Thermostatic control is simple and accurate. Fan-assisted models spread heat evenly. Installation is minimal—just a weatherproof socket and, ideally, an external RCD-protected supply.

Cons: Running costs are the real drawback. A 2kW heater left on continuously through a hard winter can cost £250–400 depending on your electricity rate. Even with a thermostat cycling it on and off, costs add up in cold snaps. Many UK properties also don't have dedicated garden circuits rated for continuous outdoor use, and running a heater via an extension lead is a fire hazard.

Best for: Smaller glasshouses (under 8m²), or growers who heat only occasionally or for short spells. Also ideal if you have off-peak electricity rates or solar panels.

Paraffin Heaters: Traditional, Portable, Fairly Economical

Paraffin (kerosene) heaters are common in UK glasshouses and represent the middle ground between cost and effort. You buy jerry cans of fuel, fill the heater's tank, light it (or use electronic ignition on newer models), and it produces steady radiant heat.

Pros: Fuel is relatively cheap—roughly £7–10 per litre—and one tank often runs for several days of background heating. No electricity needed; some models are entirely fuel-fired. Radiant heat feels pleasant and warms solid objects directly. Portable and work in any glasshouse without modifications.

Cons: Paraffin combustion produces water vapour as a by-product, which raises humidity significantly. This increases fungal disease risk unless you ventilate regularly—defeating some heat-saving gains. You must handle, store, and clean up fuel, and the smell persists. Incomplete combustion can damage plants, so cheap heaters or poor maintenance are risky. Refilling every few days in peak winter is tedious. Safety concerns exist around tipping and fire hazard if knocked over; they also require proper ventilation if used in sealed spaces, though glasshouses aren't usually completely airtight.

Best for: Medium-sized glasshouses (8–15m²) where you don't mind the fuel handling and humidity trade-off. Good if electricity supply is limited. Less suitable for plants sensitive to humidity swings.

Bio-Ethanol Heaters: Clean-Burning but Pricier Fuel

Bio-ethanol heaters are a newer option in UK glasshouses. They burn bioethanol (a plant-derived alcohol fuel) and produce only heat, water vapour, and carbon dioxide—no soot or odour.

Pros: Cleaner combustion than paraffin. Less smell. Radiant heat with no fans needed. Fuel stores safely and is less hazardous than paraffin. No electricity requirement.

Cons: Bioethanol fuel costs roughly £15–25 per litre, making running costs substantially higher than paraffin—sometimes comparable to electricity for continuous heating. Also produces humidity, so ventilation is still necessary. Fewer fuel suppliers in rural areas; you may struggle to source fuel reliably. Heater choice is more limited than for paraffin or electric models.

Best for: Growers prioritising minimal smoke and smell, or those with strong environmental preferences. Less practical as a primary heat source for tight budgets, but excellent for supplementary heating or smaller spaces where fuel consumption is low.

Insulation: The Unsung First Step

Before committing to a heater, insulate your glasshouse. This directly reduces how much heat you need to generate. Bubble wrap—especially the larger-bubble version—is the go-to method in UK glasshouses. Tape it to the inside of glass panels in autumn, leaving the roof clear to admit winter light (which is precious and helps plants photosynthesize). A single layer cuts heat loss by around 30–40%. Double-layer bubble wrap (or specialist glasshouse insulation film) does better but blocks more light.

Ground-level insulation matters too. Lining the base with straw or fleece reduces upward heat loss. Shade cloth or old bubble wrap can also be hung inside on cold nights and removed during the day to maximise solar gain.

Cost is low—a roll of bubble wrap costs £10–20—and it works with any heating method.

Temperature Monitoring and Control

Whichever heater you choose, install a reliable thermometer or thermostat. Cheap dial thermometers are inaccurate; a digital max-min thermometer (£10–20) shows you the coldest temperature reached overnight, which is essential for knowing whether your heating is working.

Many electric heaters have built-in thermostats, but paraffin and bio-ethanol models often don't. A separate thermostat controller that triggers a heater via a relay is possible but complicates installation. Many growers simply turn paraffin heaters on when frost threatens and off during mild spells.

The Practical Choice

Most UK glasshouse growers use a layered approach: good insulation as a foundation, then paraffin heating for reliable, economical background warmth through winter, plus an electric fan heater as backup for the coldest weeks. This spreads cost and risk. If electricity is expensive, paraffin alone may be better. If you have off-peak rate access, electric heating shines.

Start with insulation and monitoring. Once you know how much heat you actually need, choosing a heater becomes clearer—and your fuel bills will thank you.