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Greenhouse Heaters

The right greenhouse heater keeps frost off tender plants through winter and lets you start crops weeks earlier in spring. As a rough guide, a 2kW heater holds a 6x4 or 8x6 frost-free, while glass-to-ground, timber, and anything 8x8 and up wants 3kW or more. Heaters here start at £140.

What matters most is the thermostat, not the badge. A heater on a tight thermostat holds your target 5°C frost guard or 10°C growing temperature without the swings that stress plants, and without burning electricity you do not need.

Size to the Space 2kW for a 6x4-8x6, 3kW+ for bigger
Thermostat Is Key Holds temperature, cuts running cost
Three Fuels Electric, gas or paraffin
Free Delivery UK mainland shipping included
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Need Help Choosing?

Which greenhouse? Compare glazing, sizes and styles to find your match. Buyer's guide Materials, sizing, glazing and prices explained. Installation Base prep, assembly and our professional fitting service.

Or call our team free on 0800 098 8877

About Our Greenhouse Heaters

A heater turns a summer greenhouse into a year-round one. Hold it just above freezing and you can overwinter geraniums, fuchsias and citrus; push it to 10°C and you can sow weeks before anyone with an unheated house. We stock electric, gas and paraffin heaters from Eden, Palram Canopia and Elite, from £140.

Two things decide which heater you need: the size of the greenhouse and whether you have power to it. A 2kW electric heater holds frost off a 6x4 or 8x6. Larger or glass-to-ground houses lose heat faster and need 3kW or a gas heater. No mains supply? Gas or paraffin run independently, though they add moisture you must vent.

Why We Chose This Range

"People ask me which heater is cheapest to run, and the honest answer is the one with the best thermostat, whatever the fuel. I have watched a cheap heater with a crude dial burn money holding a greenhouse far warmer than it needed. Electric with a proper thermostat is the cleanest for most people. I keep gas and paraffin for plots with no power, but you have to crack a vent because they put water into the air as they burn."

— Matt, Founder of Greenhouse Stores

💡 Tip: Heat a smaller space, not the whole greenhouse. Curtaining off one end with bubble insulation, or standing tender plants together under fleece, lets a 2kW heater do the work of a much bigger one.

🔧 Matt's Installation Tip: Get electric power in safely

A greenhouse is a wet place full of metal, so electric heating needs an outdoor-rated supply on an RCD, ideally a proper armoured cable run by an electrician, not an extension lead trailed across the lawn. Stand the heater clear of foliage and let it draw and blow air freely.

Matt's Pick: Palram Canopia 2400W with thermostat

Best For: A mains-powered 6x4 to 8x6 that needs reliable frost protection.

Why I Recommend It: The built-in thermostat is the bit that saves you money. It holds your set temperature and switches off the moment it is reached, so you are not paying to overheat.

Price: from £199

Greenhouse heater fuels compared

FuelBest forWatch out for
Electric ⭐ Matt's PickClean, thermostatic, set and forgetNeeds a safe mains supply
Gas / propanePowerful heat, no mains neededAdds moisture, must be vented
ParaffinCheap backup, frost protectionNo thermostat, adds damp

Frequently Asked Questions

  • What size greenhouse heater do I need?

    A 2kW heater suits a 6x4 or 8x6. Larger, timber, or glass-to-ground greenhouses lose heat faster and need 3kW or more. Match the heater to the space, then set the thermostat to the temperature you actually need.

  • Is electric or paraffin cheaper to run?

    It depends on control, not just fuel. Paraffin is cheap to buy but has no thermostat, so it burns constantly. Electric with a good thermostat only runs when needed, which often makes it cheaper overall and far easier to manage.

  • What temperature should I keep my greenhouse?

    Aim for 3 to 5°C to keep frost off most tender plants. Raise it to around 10°C if you want to start seeds early or grow on through winter. Every degree higher adds running cost, so heat only as much as the plants need.

  • Do gas and paraffin heaters need ventilation?

    Yes, always crack a vent with gas or paraffin. Both give off water vapour as they burn, which raises humidity and can encourage disease. A little ventilation clears the moisture while still holding useful heat.

  • Do I need to heat my greenhouse in winter?

    Only if you grow tender plants or sow early. An unheated greenhouse still keeps off the worst frost. A heater matters if you overwinter pelargoniums, citrus and similar, or want a head start in spring.