First, do you actually need heating?
The honest answer for 90% of UK domestic greenhouses: no. Insulation plus frost protection covers everything except commercial tomato/cucumber year-round production (which needs propane heat at £40-80/m² heating cost, not consumer scale).
What you need depends on which group you're in:
Group A, March to October growing (no winter use)
- No heating needed. Greenhouse sits cool November to February, deep clean in October, restart sowing in February
- Cost: £0
Group B, frost protection only (tender perennials, kept above 3°C)
- 1 KW oil-filled radiator on thermostat, OR ceramic frost watcher (~£40-60)
- Bubble-wrap insulation reduces running cost by 40-50%
- Cost: £40-80 heater plus ~£80-150/winter electricity
Group C, cool greenhouse (5-10°C, salad plus hardy crops winter)
- 2 KW heater on thermostat
- Heavy insulation essential (bubble-wrap plus sealing all gaps)
- Cost: £80-150 heater plus ~£200-400/winter electricity
Group D, warm greenhouse (15-20°C, year-round tomato/cucumber)
- Propane / commercial heater 3-5 KW
- Triple-skin polycarbonate or heavily insulated
- Cost: £200-400 heater plus ~£600-1,500/winter gas (NOT recommended at UK domestic scale, the economics don't work)
Which group are you in? Most UK greenhouse owners shopping "greenhouse heater" actually want Group B (frost protection) but read advice for Group D and overspend.
Insulation FIRST, then heater
The biggest mistake: buying a heater without insulating. Heat escapes through:
- Single-glass panels: U-value ~5.8 W/m²K (high heat loss)
- Twin-wall polycarbonate (NORDIC CrystalLight): U-value ~3.9 W/m²K (~33% better than glass)
- Air gaps around vents, door, base sills
Bubble-wrap (Plantawrap or equivalent UV-stabilised greenhouse bubble) reduces U-value by ~40%. For a 7.8 m² greenhouse (NORDIC M), this means:
| Setup | U-value | Heating cost (frost protect) |
|---|---|---|
| Single glass, no insulation | 5.8 | ~£400/winter |
| Twin-wall PC, no insulation | 3.9 | ~£250/winter |
| Twin-wall PC plus bubble-wrap | 2.3 | ~£140/winter |
| Twin-wall PC plus bubble-wrap plus door brush seal | 2.0 | ~£110/winter |
Insulation pays back in one winter. £80 of bubble-wrap saves £100+ per winter for 5-10 years = £500-1000 saved over lifetime.
→ Deeper read: How to Insulate a Greenhouse for UK Winters
Heater types compared
Type 1: Electric oil-filled radiator (most common, recommended for frost protection)
How it works: 1-2 KW oil-filled heater, plug into outdoor-rated socket via thermostatic plug or built-in thermostat. Turns on at 3°C (frost) or 5°C (cool), maintains target temp.
Pros:
- Cleanest, no fumes, no moisture, no CO build-up
- Cheap to buy (£40-80)
- Built-in safety (tip-over cut-off, overheat protection)
- Quiet
- 95%+ thermal efficiency
- Variable wattage settings on most models
Cons:
- Needs outdoor-rated electricity (~£200-400 sparky job if not present)
- Running cost = electricity rate × wattage × duty cycle
- Limited by socket capacity (most UK 13A sockets max ~3 KW continuous)
Running cost (UK 2026, ~30p/kWh):
- Frost protection (1 KW running ~25% of winter hours): ~£130-160/winter
- Cool greenhouse (2 KW running ~40% of winter hours): ~£350-450/winter
Best for: Group B (frost protection) and lower end of Group C (cool greenhouse). A safe, domestic choice for frost protection where mains electricity is available.
Type 2: Paraffin heater
How it works: Burns paraffin (kerosene) via a wick plus reflective fins. No thermostat, burns at constant rate. ~85-90% thermal efficiency.
Pros:
- No electricity needed, fully portable
- Cheaper running cost per KW than electricity (paraffin ~£1.20-1.80/L, 1 L burns ~10 hours at 0.5 KW heat output)
- Produces moisture plus CO2, good for plants in winter (mild greenhouse effect)
Cons:
- No thermostat, runs whether needed or not (waste on mild nights)
- Open flame, fire risk if greenhouse contains combustibles
- Moisture output increases condensation plus disease risk
- CO2 plus moisture build-up needs ventilation, which defeats heating
- Smell of paraffin (not loved by everyone)
Running cost: ~£60-120/winter (less than electric for frost protection)
Best for: Off-grid greenhouses (allotments without power), or budget-tight Group B users willing to manage daily.
Type 3: Propane / butane heater
How it works: 11-13 kg gas bottle feeds a regulated burner. Can be thermostat-controlled with kit. 2-4 KW heat output.
Pros:
- High heat output per unit
- No electricity needed
- Cheaper per KW than paraffin (propane ~£60/13kg bottle = ~£0.40/kWh equivalent)
Cons:
- More expensive heater (£150-300)
- Open flame, fire risk
- CO build-up requires ventilation
- Bottle storage requirement (outdoors, regulated)
Best for: Group D commercial-scale plus off-grid serious growers. Overkill for typical UK domestic.
Type 4: Ceramic heater (small panel)
How it works: 0.4-1 KW electric ceramic panel. Some models thermostat-controlled.
Pros:
- Lowest-cost electric option (£25-50)
- Compact, easy to position
- Fast-warming
Cons:
- Lower output, doesn't cover large greenhouses well
- Most models no thermostat, run constantly
- Higher running cost per useful heat (less efficient than oil-filled)
Best for: Tiny greenhouses (<5 m²) frost protection only.
What to buy for your situation
Group B (frost protection, December to February, just keeping plants alive):
- Buy: 1 KW oil-filled radiator with thermostat (set 3°C)
- Insulate: bubble-wrap inside polycarbonate panels
- Cost: £60-80 heater plus £40-60 bubble-wrap plus £120-150 winter running = ~£250-300 first winter, £130-150 per subsequent winter
Group C (cool greenhouse, salads plus hardy through winter):
- Buy: 2 KW oil-filled radiator with thermostat (set 5-7°C)
- Insulate: bubble-wrap plus door brush seal plus ventilator covers when not opening
- Cost: £100-150 heater plus £80 insulation plus £300-450 winter running = ~£500-700 first winter, £350-450 subsequent
Group D (warm year-round growing, generally not economic at UK domestic scale):
- Reality check: heating 13 m² to 18°C through UK November to February costs £800-1,500/winter in gas alone
- For comparison: that's ~£100/kg of tomatoes at supermarket prices, plus all your time
- Only makes sense for commercial market gardeners or those with very high ornamental value (orchids, exotic perennials, and the like)
Don't overspend, match scale to use case
UK greenhouse heating mistakes are uniformly overheating: buying heaters meant for commercial nurseries (3-4 KW) for a 7 m² domestic frost-protection scenario, then complaining about £400/winter bills.
Match wattage to volume: rough rule 0.15-0.2 KW per m² floor area for frost protection, 0.3-0.4 KW/m² for cool greenhouse, 0.6-1 KW/m² for warm. For NORDIC M (7.8 m²): frost protection = 1.2-1.5 KW heater (a 1 KW or 2 KW oil-filled is plenty).
Power supply, the often-overlooked cost
Greenhouse power supply isn't free. If you don't have an outdoor-rated socket within reach:
| Solution | DIY? | Cost |
|---|---|---|
| Extension reel from house (NOT recommended long-term) | DIY | £30-60 plus risk |
| Outdoor weatherproof socket installed by sparky | Pro | £150-300 |
| Buried armoured cable to dedicated greenhouse socket | Pro | £300-600 |
| Solar panel plus battery (off-grid frost protection) | DIY-ish | £200-500 setup |
Extension reels are a fire hazard. They're not designed for sustained outdoor use, and the IP rating won't survive UK winter weather. Pay a sparky for proper installation; it's a one-time £200-400 cost that lasts the lifetime of the greenhouse.
Greenhouse heating safety
The 3 risk categories:
1. Fire risk. Paraffin/propane open flame plus dry plant matter (canes, twine, dried leaves) = ignition risk. Never run paraffin/propane unattended overnight without proper safety distance.
2. CO poisoning. Paraffin/propane combustion produces carbon monoxide. Even with ventilation, CO can accumulate. Don't enter the greenhouse first thing in the morning without first opening the door for 10 minutes to vent.
3. Electrical risk. Outdoor plus water plus electricity is a combination requiring proper installation. RCD-protected circuit mandatory for greenhouse electrics; IP-rated outdoor sockets only; cables run in proper conduit or armoured.
Putting it together, most common UK setup
The default for ~80% of UK domestic greenhouse owners who want winter use:
Setup:
- 1 KW oil-filled electric radiator with built-in thermostat (set 3°C frost protection)
- Bubble-wrap inside polycarbonate panels Nov to Feb
- Outdoor IP-rated socket via professionally-installed armoured cable from house
- Frost-tolerant winter crops: hardy salads, garlic, winter chard, overwintering broad beans
Total cost:
- £60 heater
- £60 bubble-wrap
- £250 sparky for outdoor socket (one-off)
- ~£130/winter electricity
What you get:
- Plants survive frost
- Lemon tree / fig in pot overwinters
- Hardy salads continue cropping
- Spring sowing starts in February with propagator running on same socket
- Total ~£500 first year, ~£130/year ongoing
This is the right answer for most UK domestic greenhouse owners. Anyone trying to grow tomatoes through January is solving a problem that supermarkets have already solved: supermarket tomatoes are cheaper than your own electricity bill.
Frequently asked questions
What's the cheapest way to heat a greenhouse in UK winter?
For frost protection (3°C minimum): 1 KW oil-filled electric radiator with thermostat plus bubble-wrap insulation. Running cost ~£130/winter at 2026 electricity rates. Cheaper option: paraffin heater (~£60-120/winter) but produces moisture and CO2 plus open-flame risk.
Do I need to heat my greenhouse in winter UK?
Most likely no. If you're growing March to October only, you can leave the greenhouse unheated and let it rest from November to February. If you want frost protection for tender perennials (lemon, fig, overwintering chillies), £130/winter electric oil radiator covers it. Full year-round tomato growing in an unheated UK greenhouse doesn't work even with heat: supermarket tomatoes are cheaper than the gas bill.
What's the best greenhouse heater for the UK?
1 KW or 2 KW electric oil-filled radiator with built-in thermostat. Clean (no fumes), safe (built-in cut-off), efficient (95%+), inexpensive (£60-100). Paraffin and propane work for off-grid scenarios but introduce fire/CO risks not worth it for indoor-electric-available domestic plots.
How much does it cost to heat a greenhouse for winter UK?
At 2026 UK electricity rates (~30p/kWh), frost protection for a 7-8 m² greenhouse: ~£130-160/winter. Cool greenhouse (5-7°C): ~£350-450/winter. Warm year-round (15-20°C): ~£800-1,500/winter (not economic at domestic scale).
Can I use a paraffin heater in my greenhouse?
Yes, but with caveats. Pros: no electricity needed, cheap running. Cons: open flame (fire risk), produces moisture (humidity plus disease risk), produces CO (ventilation needed which negates heating). Best for off-grid allotments without power. Don't run overnight unattended.
Will bubble-wrap insulation save money on heating?
Yes, significantly. Bubble-wrap reduces twin-wall polycarbonate U-value from 3.9 to ~2.3 W/m²K (~40% reduction in heat loss). For a 7.8 m² greenhouse, this saves ~£100-150/winter on heating costs. £80 of bubble-wrap pays back in the first winter.
How do I keep frost out of my greenhouse cheaply?
Three-step approach: (1) insulate with bubble-wrap inside polycarbonate, (2) seal door plus vent gaps with brush seal strips, (3) install 1 KW oil-filled electric heater on 3°C thermostat. Total setup ~£200, running cost ~£130/winter. Keeps tender perennials alive without growing winter veg.
What temperature should I keep my greenhouse at in winter?
For frost protection: 3°C (just above freezing). For salad-greenhouse: 5-7°C (slow growth but plants healthy). For tomato/cucumber year-round: 15-18°C minimum (not economic UK domestic). Setting any higher than needed wastes electricity proportionally.
Can I heat a greenhouse with solar?
For frost protection only, yes, in a limited way. A 200W solar panel plus 100Ah leisure battery plus 1 KW thermostat-controlled inverter heater can manage frost protection on a small greenhouse if installed correctly. Cost ~£300-500 setup, off-grid forever. Not suitable for cool/warm greenhouse: solar yield in December to February is too low to sustain higher wattages.
Next steps
For a year-round usable greenhouse, the right structure matters as much as the right heater. Twin-wall polycarbonate (vs single glass) cuts heat loss through the glazing by roughly a third before you add insulation. NORDIC's 4 mm standard CrystalLight polycarbonate panels (U≈3.9 W/m²K) are the structural answer; bubble-wrap plus 1 KW electric radiator is the winter management answer.
→ Browse the NORDIC range, five sizes from £999 → How to Insulate a Greenhouse for UK Winters, the bubble-wrap detail → Polycarbonate Wooden Greenhouse, why twin-wall PC outperforms single glass for winter use → Wooden Greenhouse Cost UK 2026, total cost of ownership including heating
Related Reading
- How to insulate a greenhouse for UK winter, the partner piece on bubble wrap and thermal mass
- Monthly greenhouse calendar UK
- How to grow tomatoes in a UK greenhouse
- Wooden greenhouse maintenance, annual schedule
- Polycarbonate wooden greenhouse, twin-wall thermal performance
- Waldenhaus wooden greenhouses, main hub
- Shop the NORDIC range, from £999
