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Plant heater buying guide

Updated: October 2026

A plant heater on amazon.co.uk can be a 17.5 W tray mat, a 12 W windowsill propagator, a shed tube, or a 120 V tent heater that will not run on a UK socket. This buying guide is the choice before stars: a seed tray, a kitchen sill, or a greenhouse that must stay above freezing. Name the job first. A claimed band only helps once you know whether you are heating compost or air. The listings are in our [plant heater comparison](/hub/plant-accessories/plant-heater). The Products Compared editorial team checked them on 16 October 2026. We did not run a lab test. A qualifying purchase can earn us a commission at no extra cost to you.

A plant heater on amazon.co.uk can be a 17.5 W tray mat, a 12 W windowsill propagator, a shed tube, or a 120 V tent heater that will not run on a UK socket.

Our top picks

HBN HBN 17.5 W seedling mat

Best overall

HBN HBN 17.5 W seedling mat
9.2/10about £14.99
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EarlyGrow EarlyGrow 3-bay heated propagator

Rank 2

EarlyGrow EarlyGrow 3-bay heated propagator
9.0/10about £42.95
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Airmaster Airmaster 520 W frost convector

Rank 3

Airmaster Airmaster 520 W frost convector
8.6/10about £25.94
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On this page
  1. 1.Four tools, one search phrase
  2. 2.A setpoint you can change
  3. 3.230 V, a BS 1363 plug, and a 120 V listing
  4. 4.IP codes and watts for the space you actually have

Four tools, one search phrase

Shoppers use one phrase for four tools. A seedling heat mat sits under a tray at about 17.5–20 W. A heated propagator adds a lid: the EarlyGrow is 12 W at a fixed band of about 16–19°C. A greenhouse heater moves air. The LightHouse tube is about 45–50 W, the Morris tube is 120 W, and the Airmaster convector is 520 W with a thermostat. The Royal Horticultural Society says many seeds germinate around 18°C. Holding a glasshouse near 4°C on a frost night is a different target. If the air in the house must stay above freezing, a mat will not do it.

A setpoint you can change

A printed band is not a thermostat. The HBN 17.5 W mat at £14.99 prints 230–240 V and claims about 24–30°C, with no dial and no timer. The Levson 20 W mat prints IP65 and 230 V at £14.36, and reviews say seedlings cooked because there is no setting. The EarlyGrow band of about 16–19°C is gentler on paper, and you still cannot turn it down on a sunny sill. A controller can still fail. The AOOWU claims 20–45°C, though wattage and voltage are not printed. The HBN combo claims 5–42°C, and some reviews say the setpoint did not stick. The WADEO pair shares one controller, and reviews mention soil that overshoots. The Morris tube has a cut-out, and reviews say there is no dial.
HBN HBN 17.5 W seedling mat

Testsieger

HBN HBN 17.5 W seedling mat
9.2/10about £14.99
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230 V, a BS 1363 plug, and a 120 V listing

UK mains are 230 V. An appliance for a UK domestic socket should carry a BS 1363 plug, the point of regulation 35 of the Electrical Equipment (Safety) Regulations 2016. The EarlyGrow states a UK plug and 220–240 V, and the listing says it is made in the United Kingdom. The HBN 17.5 W mat and the Levson print a 230 V or 230–240 V supply. The AOOWU, the HBN combo, the WADEO set, and the RC SLL mat do not print voltage. Missing voltage is a reason to pause. The THERMOFORGE T7 at £119 prints 120 V AC, and this file does not show a BS 1363 plug. A 4.3 from 57 reviews, mostly from the United States or Canada, does not make it a UK appliance. One Ireland Levson review received an EU plug twice although the picture showed three pins. A greenhouse circuit should be on a 30 mA RCD.

IP codes and watts for the space you actually have

Waterproof without a code is a wipe-clean claim. IPX4 on the AOOWU is splash resistance, and the listing still says not to immerse the mat. IP20 on the Airmaster is a dry indoor rating, while the blurb mentions greenhouses. IP55 on the Morris tube and IP65 on the Levson are higher jet ratings. Mats here are about 12–50 W, which is a tray. The LightHouse at about 45–50 W and the Morris at 120 W are background warmth. The Airmaster is 520 W with a stated cover of up to 10 m². About 1 kW for a small insulated 6 × 8 ft greenhouse is a writer’s rule of thumb, not an RHS table. Compost versus air is seedling heat mat or greenhouse heater. If two products remain, best plant heater names one top pick and one best value.

Common questions

Is a seedling heat mat a greenhouse heater?
No. A mat in this set is about 12–50 W under a tray. The RHS treats a heat mat as a way to warm seed compost, often around 18°C. Holding greenhouse air above freezing is a different job. Use the mat for compost and size an air heater separately.
Do you need a thermostat, or is a claimed 20–30°C band enough?
A claimed band is not a setpoint. The HBN 17.5 W mat and the Levson stay on, and reviewers report cooked seedlings where there is no dial. You want a thermostat if you will be away, or if you need about 18°C for seed or about 5°C for pelargoniums.
What plug and voltage should a UK plant heater have?
Look for 220–240 V or 230 V on the listing, and a BS 1363 plug. Regulation 35 of the Electrical Equipment (Safety) Regulations 2016 is the plug rule. The EarlyGrow states a UK plug and 220–240 V. A listing that prints 120 V, such as the THERMOFORGE T7, does not match UK mains. If voltage is missing, treat it as unknown.
What is the difference between waterproof, IPX4, IP20, IP55, and IP65?
Waterproof with no code, as on the HBN mat, usually means you can wipe it. IPX4 is splash resistance. IP20, which the Airmaster prints, is a dry indoor rating. IP55 and IP65, on the Morris tube and the Levson, are higher jet ratings. None of these codes say you should immerse the heater or stand it in a puddle.
When should you call an electrician instead of buying another heater?
Call an electrician for a new greenhouse supply, a burning smell, a cracked plug, or if you do not know whether the socket is on a 30 mA RCD. New fixed wiring in England and Wales is Building Regulations Part P work. Do not keep using a heater that smoked on first switch-on while you shop for more watts.

Related pages

How to use a seedling heat mat

Greenhouse frost heater

Plant heaters

Best plant heater: windowsill top pick in this set

Seedling heat mat or a greenhouse heater for the UK

Sources

Public UK sources for greenhouse heat, sowing temperature and electrical safety, plus the amazon.co.uk listing facts in the display file. Shelf prices and star lines are those captured figures, not a live re-check.

  1. RHS: heating greenhouses efficiently (retrieved 16 October 2026)
  2. RHS: electricity in the garden (retrieved 16 October 2026)
  3. RHS: sow seeds indoors (retrieved 16 October 2026)
  4. RHS: April greenhouse jobs (retrieved 16 October 2026)
  5. Electrical Equipment (Safety) Regulations 2016, regulation 35 (retrieved 16 October 2026)
  6. NICEIC: gardens and electrics (retrieved 16 October 2026)
  7. Gardeners' World: heated propagators (retrieved 16 October 2026)
  8. Thompson & Morgan: heating a greenhouse (retrieved 16 October 2026)