The best seedling heat mats, compared.
Top pick: RC SLL 18 W four-pack title Best value: HBN 17.5 W fixed heat mat – About £14.99 with 4.6 from 283 reviews, the lowest price in this set at 4.4 or above with at least 200 reviews. Updated October 2026.
A seedling heat mat is a flat electric pad that warms compost from below so seeds germinate in a cool British house or greenhouse. That is common for tomatoes, peppers, chillies and aubergines from February, and a poor idea for lettuce and peas. The Royal Horticultural Society says most seeds need about 18°C and that the packet wins. Chillies are about 21°C, sweet peppers 18–21°C, and aubergines at least 21°C. The useful differences are the heated rectangle, a set temperature, and a fused BS 1363 plug. A fixed mat adds a lift above the room. The English puts a 17.5 W mat at about 8°C above ambient. It does not hold a set compost temperature. Bottom heat is for germination, not for growing on. Leaving the mat on after emergence is a usual route to leggy plants. The checks are in the [seedling heat mat buying guide](/hub/plant-accessories/seedling-heat-mat/sub/seedling-heat-mat-buying-guide). You buy one when the packet wants more warmth than the room holds overnight.
A seedling heat mat is a flat electric pad that warms compost from below so seeds germinate in a cool British house or greenhouse.
42 products checked · 62 hrs invested · +21,400 readers
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Personal buying guide
Question 1 of 2
What do you need the mat to do?
The RC SLL listing is about £42.99, the highest price in this set, with 4.7 from 46 reviews. The title says a four-pack of 18 W mats, each about 10 × 20.75 in, and reviews say four mats arrived. One bullet says the package includes only one pad, and that 2-packs and 4-packs exist. No thermostat is in the box. A bullet recommends an RC SLL thermostat separately. Voltage is not printed. A review quotes a do-not-submerge line printed on the mat. The 4.7 line is the highest star rating here, and the pack conflict plus the missing setpoint are why it is not the top pick.
Pros
Cons
Best for: Several trays on fixed mats, if the box that arrives matches the four-pack title and the reviews.
Less suitable: A setpoint, or a buyer who needs the listing to agree with itself on the pack count.
Specifications
Common questions
Does the box contain four mats?
The title says 4 pack, and reviews say four mats arrived. One bullet says the package includes only 1 pad and that 2-packs and 4-packs exist. The file keeps both lines.
Is a thermostat included?
No. A bullet recommends an RC SLL thermostat. Power-off protection is named and not defined. Voltage is not printed.
What size is one mat?
10 × 20.75 inches, also given as 52.71 × 1.27 × 25.4 cm, at 18 W per mat as written. A review quotes a do-not-submerge line printed on the mat.
The HBN CP-C93 is a 17.5 W mat at about £14.99, printed for 230–240 V, with a heated area of 25 × 50 cm. amazon.co.uk shows 4.6 from 283 reviews, the longest file among the fixed mats here. The listing claims about 24–30°C and tells you to leave it on for 24 hours. That band is a description, and there is no dial. Reviews use it under tomato and pepper trays, and they also report uneven heat, no timer, and at least one mat that stopped after a month or two. Waterproof is wording only, with no IP code. It is the best value in this set because it is the lowest price at 4.4 or above with at least 200 reviews. A cold night still changes the compost, because the mat only adds a lift above the room.
Pros
Cons
Best for: One seed tray on a windowsill when you will unplug the mat once the seedlings are up.
Less suitable: A greenhouse whose nights swing, or any crop that needs a set compost temperature.
Specifications
Common questions
Can you set the temperature on this HBN mat?
No. The listing claims about 24–30°C and says to leave it on 24 hours. Reviews say there is no temperature control and no timer.
What size is printed?
The listing states 10 by 20 inches, also given as 25 by 50 cm. The package line is 26.5 × 7.2 × 7.2 cm and 270 g.
Is waterproof the same as an IP code?
No. This listing says waterproof PVC. It does not print an IP code, and it does not state an immersion test.
The Senua mat is about £14.99, the same shelf price as the fixed HBN, at 20 W and 25 × 52.7 cm. amazon.co.uk shows 4.6 from 66 reviews. There is no thermostat, so the control is the plug. The bullets claim IP67 and include the listing’s own sentence of 1 m for 30 minutes. Voltage is not in the spec table. One review mentions a UK plug and a 3 A fuse, which the specification does not. Reviews say the edge stays cool, and that the pad is larger than one standard tray and short of two full trays. A printed IP code is a test description under BS EN 60529, and this page still gives you no permission to submerge the mat.
Pros
Cons
Best for: One tray when you want a claimed IP67 mat at the HBN’s price and you will check the plug in the photos.
Less suitable: A setpoint, or two Thompson & Morgan full trays edge to edge.
Specifications
Common questions
Does this Senua mat have a thermostat?
No. It is plug-in only. Reviews say the only control is unplugging or a separate timer plug, and that compost temperature should be checked.
What does the IP67 line say?
The bullets claim IP67 and include the listing’s own sentence of 1 m for 30 minutes. Voltage is not printed.
Will it cover two full British trays?
The heated area is printed as 25 × 52.7 cm. Reviews say that is larger than one standard tray and short of two full trays, and that the edge stays cool.
The AOOWU JX02 is about £18.99, with a title size of 52.5 × 25 cm and a controller stated at 20–45°C. amazon.co.uk shows 4.6 from 11 reviews. Wattage and voltage are not printed. IPX4 is printed, and the listing says not to immerse the mat and not to use it to heat a person. A separate probe is not named. Seven stored review texts also appear on the 52 × 52 cm AOOWU, so they do not describe this size on their own. A 4.6 from 11 is a thin sample beside the HBN’s 283 reviews. It is the lowest thermostat price in the set, and the missing supply figures are why the score stays mid-table.
Pros
Cons
Best for: A narrow tray when you want a stated 20–45°C band and you can accept a short, shared review file.
Less suitable: Anyone who needs a printed wattage, a named voltage, or reviews that describe this size.
Specifications
Common questions
Does this mat name a wattage or a voltage?
No. Both are absent from the file. The stated control range is 20–45°C, and IPX4 is printed.
Can you immerse it?
The listing says do not immerse it, and do not use it to heat a person. IPX4 is the printed code.
Do the reviews describe this size?
Seven stored texts are in the file, and the same seven appear on the 52 × 52 cm AOOWU. They do not describe this size on their own.
The AOOWU JX03 is about £24.99, with a title size of 52 × 52 cm and the same stated 20–45°C control as the narrower AOOWU. amazon.co.uk shows 4.6 from 11 reviews. Wattage and voltage are not printed. IPX4 is printed, and the listing says not to immerse the mat. The seven stored texts match the 52.5 × 25 cm listing and do not mention the square size. A separate probe is not named. The package line is 34.5 × 22.8 × 5.4 cm and 810 g, which is the parcel, not a second heated area. You pay more than for the narrow AOOWU for a footprint the review file does not describe.
Pros
Cons
Best for: Two small pots side by side if the square arrives as titled and a shared review file is enough for you.
Less suitable: Anyone who wants reviews of this footprint, or a printed wattage.
Specifications
Common questions
How big is the heated area?
The title says 52 × 52 cm. The package line is 34.5 × 22.8 × 5.4 cm and 810 g. Wattage and voltage are not printed.
Is a separate probe named?
No. A control device at 20–45°C is stated. A separate probe is not named. The listing says do not immerse the mat.
Do the reviews cover this square mat?
The seven stored texts match the 52.5 × 25 cm AOOWU. They do not mention the square size.
The WADEO HG0281EU is a 50 W mat at about £24.22, sized 52 × 25 × 0.2 cm, with a separate probe and a digital range of 5–45°C. amazon.co.uk shows 4.5 from 404 reviews, the longest file in this set. Stored reviews praise germination and the thermostat, and they also report a hotter centre, fussy probe placement, failed displays, and one report of a fire. The model code ends in EU, the technical language field repeats German, and the plug is not named, so the photo has to show a BS 1363 plug before you trust the socket. Voltage is not printed beyond a power-source type of ac_dc. It is the top pick here because a setpoint plus 404 reviews outscores every other listing after those deductions. It is dearer than the fixed HBN, which is the best value.
Pros
Cons
Best for: Windowsill tomatoes, peppers or chillies when the room swings and you will check the plug in the photos.
Less suitable: A buyer who will not look at the plug, or two mats that must sit at different temperatures.
Specifications
Common questions
What temperature can you set?
The listing states a digital thermostat from 5°C to 45°C with a separate probe, in °C and °F. A clock timer is not stated.
Is the plug named?
No. The model code is HG0281EU, and the technical language field repeats German. Voltage is not printed beyond a power-source type of ac_dc.
What do the reviews say about the controller?
The first 50 stored reviews praise germination and the thermostat. They also report centre-hot mats, fussy probe placement, and controllers or displays that fail.
The WADEO MS-HG0429UK is about £25.75, at 50 W and 52 × 25 cm, with a separate probe and a stated range of 5–45°C. amazon.co.uk shows 4.5 from 21 reviews. The stored texts match the two-mat ASIN, so this file is not an independent sample. One review saw a range of 5–40°C on the unit in hand. Power-cut resume is claimed, and a clock timer is not. The model code ends in UK. That is not a plug specification, and the listing does not name the plug or the voltage. A shared review mentions IP67, which the bullets on this ASIN do not print.
Pros
Cons
Best for: One 52 × 25 cm mat when you want this model code and you will still check the plug in the photos.
Less suitable: Anyone treating 21 shared reviews as a test of this single mat on its own.
Specifications
Common questions
Does the model code mean a UK plug?
The part number is MS-HG0429UK. The listing does not name the plug or the voltage. A code ending in UK is not a plug specification.
Is there a clock timer?
No. Power-failure auto-resume is claimed. A clock timer is not stated on this ASIN.
Can the reviews be read as this mat alone?
The stored texts match the two-mat ASIN. One long review is about a single mat at a 13°C set point. Another describes two mats.
The WADEO MS-HG0430UK is about £36.09. The title says one thermostat for two mats, and it also says 104 × 50 cm. The dimensions line says 52 × 25 × 1 cm and 870 g. amazon.co.uk shows 4.5 from 21 reviews, and the stored texts match the single-mat UK model: one text is about a single mat, and another describes two mats of 52 × 25 cm. The listing states 50 W per mat. If the title is right, both mats share one setpoint, so two crops cannot sit at different temperatures. The file does not settle how many mats or which size are in the box, and the plug and voltage are not named.
Pros
Cons
Best for: A buyer who has checked the current photos for two mats and accepts one shared setpoint.
Less suitable: Two crops that need different temperatures, or anyone who needs one agreed size.
Specifications
Common questions
How many mats are in the box?
The title and bullets say two mats and one controller. The product dimensions line says 52 × 25 × 1 cm. A shared review also says two mats of 52 × 25 cm. The file does not resolve this.
Can the two mats sit at different temperatures?
No, if the title is right: one thermostat serves both. Reviews that describe two mats make the same point.
Is the size 104 × 50 cm?
That figure is in the title, including a line that calls each mat 104 × 50 cm. The dimensions line is 52 × 25 × 1 cm. Keep both.
The HBN thermostat combo is about £27.99, with a 17.5 W mat and a sensor probe stated at 5–42°C, which the listing also gives as 40–108°F. amazon.co.uk shows 4.4 from 48 reviews. The heated area is not printed. The package line is 26.9 × 13.8 × 9.5 cm and 1.04 kg, and a review says the mat did not cover two trays. The bullets say the thermostat can handle up to 2000 W, which is the controller claim, while the mat itself is 17.5 W. Error codes E1, E2 and E3 are named and not defined. Voltage is not printed, and a clock timer is not stated.
Pros
Cons
Best for: A 17.5 W mat you want on a probe, once you can measure the pad that arrives.
Less suitable: Anyone buying on a stated tray size, or a written guide to the error codes.
Specifications
Common questions
What can you set?
The thermostat is stated at 40–108°F, which the listing also gives as 5–42°C, with a sensor probe. A clock timer is not stated.
How big is the mat?
The heated area is not printed. The package line is 26.9 × 13.8 × 9.5 cm and 1.04 kg. A review says it did not cover two trays.
Is the controller claimed to run only this mat?
The mat is 17.5 W. The bullets say the thermostat can handle up to 2000 W. One reviewer used it on three mats with a plug strip. Voltage is not printed.
The WADEO HG0380UK is about £26.64, with 30 W stated, a 54 × 27 cm mat, a probe at 5–45°C, and a 0–12 hour timer. amazon.co.uk shows 4.4 from 23 reviews. Setting the timer to 0 hours means continuous heating. An Ireland review says that setting 24 does not mean 24-hour running. A reviewer’s meter read about 22 W against the stated 30 W. Reviews also report a cold border of about 20–25 mm, a mat that is hard to lay flat after being packed folded, and one controller that died after 42 days. Voltage is not printed. It is the only listing in this set with a clock timer, and the short file is why it sits below the 404-review WADEO.
Pros
Cons
Best for: A sowing spell you want to switch off after a set number of hours, once you know that 0 means always on.
Less suitable: A 24-hour programme, or a buyer who will set 24 and expect the mat to stay on.
Specifications
Common questions
How does the timer work?
The range is 0–12 hours. 0 hours means continuous heating. A timed setting switches off when the time ends. An Ireland review says setting 24 does not mean 24-hour running.
Is 30 W what a reviewer measured?
30 W is the stated wattage. A reviewer’s energy meter read about 22 W. Voltage is not printed.
Does the whole mat warm?
A review reports a cold border of about 20–25 mm. Another says the mat is hard to lay flat after being packed folded, and one controller died after 42 days.
The HYDGOOHO BHD-100 is about £25.99, with 18 W and 220–240 V at 50 Hz printed, and a heated area of 53 × 25 cm. amazon.co.uk shows 4.0 from 35 reviews. IP67 is claimed. The bullets describe a lift of 10–20°F over the room, the dial range is not printed, and a reviewer’s meter read about 7 W against the 18 W nameplate. Keep 18 W as the printed figure and treat the meter as one review. Other reviews say it would not reach 25–27°C, that about an inch of the edge stayed cold, or that the unit stopped, while one reviewer called germination their best. The printed voltage is the strength, and the 4.0 from 35 is the weak point.
Pros
Cons
Best for: A buyer who wants 220–240 V printed on a thermostat mat and will check the draw with a meter.
Less suitable: Anyone who needs the dial range written in the listing, or a long review file.
Specifications
Common questions
What voltage is printed?
220–240 V at 50 Hz, and 18 W. A reviewer’s meter read about 7 W. Treat the meter note as a review, not as the nameplate.
Is the set-point range printed?
The bullets claim 10–20°F over ambient. The dial range is not in the bullets. A review describes °C/°F and a sensor with a suction cup.
Did it hold a high set point in reviews?
One reviewer called germination their best and praised a bright display. Others said it would not reach 25–27°C, that about an inch of the edge stayed cold, or that the unit stopped.
The Gsycle pad is listed at about £8.90, with a title size of 22.1 × 15.7 cm and a technical line of 1 × 0.99 × 1 cm. amazon.co.uk shows 3.2 from 12 reviews. The page claims three gears and a band of about 40–45°C, and it prints neither wattage, voltage nor a plug. Reviews call it USB-powered, and one says two USB socket outlets were damaged. Another review measured at least 50°C on the lowest gear, so those gears are a rough switch rather than a compost setpoint. The Electrical Equipment (Safety) Regulations 2016 start at 50 V AC, which puts this pad outside the 17.5–50 W mains mats in the same comparison. It is the cheapest listing here, and the star line is the weakest.
Pros
Cons
Best for: A very small pad you will power only from a USB supply you can afford to lose, and check with a thermometer.
Less suitable: A windowsill seed tray on mains, or any socket you cannot replace.
Specifications
Common questions
Does the listing state the power supply?
No. Wattage, voltage, current and plug are not printed. Reviews say it is USB-powered, and one says two USB socket outlets were damaged.
Can you set a compost temperature?
The listing describes three gears and a claimed band of about 40–45°C. A review measured at least 50°C on the lowest gear. There is no probe thermostat.
What size is printed?
The title says 22.1 × 15.7 cm. The technical dimensions line says 1 × 0.99 × 1 cm. Both lines are in the file.
Twelve seedling heat mats on amazon.co.uk were scored from the listing facts in this set on 16 October 2026. The editorial score uses five blocks that sum to 100, then deductions for shared review texts, an EU model code with an unnamed plug, a size or pack clash, a reviewer meter well below the printed wattage, or a report of damaged USB outlets. Price in this set is one block. It does not override a higher score. There was no lab germination test. Stars and review counts are the amazon.co.uk lines in the display file.
Stars
24%The amazon.co.uk rating divided by 5, then multiplied by 24, and rounded to the nearest integer. The star line is the start of the score, not a lab result.
Review volume
22%200 or more reviews score 22. A file of 50–99 scores 14, 20–49 scores 8, and 10–19 scores 4. A short file cannot outrank a long one on stars alone.
Control
28%A probe with a printed °C range and a 0–12 hour timer scores 28. A probe with a printed °C range scores 26. A claimed thermostat without a named probe or a printed dial range scores 18. A fixed mat with a printed wattage scores 12. Three gears and no probe score 6.
Spec clarity
16%Four points each, and only when the listing prints it: wattage, voltage, one heated-area figure, and an IP code (IPX4 or IP67). A size or pack contradiction scores 0 for the area point.
Price in this set
10%Under £15 scores 10. £15–£24.99 scores 7. £25–£29.99 scores 5. £30 or more scores 3. The best-value badge is a separate rule: the lowest shelf price at 4.4 or above with at least 200 reviews.
Start with the crop and the night temperature, then with whether you can set a point, then with the heated rectangle. Watts, the plug and the water line come after. The notes below follow that order for these twelve listings.
A seedling heat mat is a flat electric pad that warms compost from below so seeds germinate in a cool British house or greenhouse. You buy one when the packet wants more warmth than the room holds overnight. That is common for tomatoes, peppers, chillies and aubergines from February, and a poor idea for lettuce and peas. The Royal Horticultural Society says most seeds need about 18°C and that the packet wins. Chillies are about 21°C, sweet peppers 18–21°C, and aubergines at least 21°C.
A 50 W mat and an 18 W mat can share a similar footprint, and a title size can disagree with the dimensions line. Measure the heated area against the tray, not against the wattage alone.
A fixed mat only lifts the room. It does not hold 21°C. A dome in sun on top of that lift is a usual route to leggy plants. Vent the lid once seedlings are up, then switch the mat off.
IP67 is a temporary immersion description under BS EN 60529. The waterproof listings still say not to immerse the mat. Wipe spills and keep the controller dry.
Match the packet before the brand. Most seed wants about 18°C. Chillies are about 21°C, sweet peppers 18–21°C, and aubergines at least 21°C. Lettuce and peas are a poor fit for a hot mat. Bottom heat is for germination. RHS chilli advice then moves seedlings to bright light at 16–18°C. A fixed mat adds a lift. The English Garden puts a 17.5 W mat at about 8°C above ambient. A thermostat holds a set point when the room swings.
Mains mats here are 17.5–50 W. Only the fixed HBN prints 230–240 V, and only HYDGOOHO prints 220–240 V at 50 Hz. Everyone else leaves voltage off the spec table. A BS 1363 plug is required for a domestic appliance under the Electrical Equipment (Safety) Regulations 2016, regulation 35, and several listings never name the plug. HG0281EU, with a German-language field, is a reason to read the photo. A model code ending in UK is not that plug.
Three typical situations, each with a recommendation from this comparison.
The room swings overnight and the packet wants more than the house holds. The WADEO HG0281EU is about £24.22, with a probe at 5–45°C and 4.5 from 404 reviews. The model code ends in EU and the plug is not named, so check the photo for a BS 1363 plug.
You want a lift for a fortnight, not a setpoint. The HBN CP-C93 is about £14.99, 17.5 W at 230–240 V, 25 × 50 cm, with 4.6 from 283 reviews. There is no thermostat. Unplug it once the seedlings are up.
You want the mat to switch off after a set number of hours. The WADEO HG0380UK is about £26.64, with a probe at 5–45°C and a 0–12 hour timer. 0 hours means continuous. A reviewer meter read about 22 W against the stated 30 W.
In this set of twelve amazon.co.uk listings, the top pick is the WADEO HG0281EU at about £24.22. It is a 50 W mat, 52 × 25 cm, with a separate probe and a printed range of 5–45°C, and 4.5 from 404 reviews. The EU model code and the unnamed plug are already deducted. Stored reviews report a hotter centre, fussy probe placement, failed displays and one fire. The best value is the fixed HBN CP-C93 at about £14.99, 17.5 W at 230–240 V, 25 × 50 cm, with 4.6 from 283 reviews and no thermostat. A cold night still changes the compost, because that mat only adds a lift above the room. None of these listings was lab-tested for germination.
HBN 17.5 W fixed heat mat
About £14.99 with 4.6 from 283 reviews, the lowest price in this set at 4.4 or above with at least 200 reviews.
Editorial
Products Compared publishes British-English buying guides based on amazon.co.uk listings and public UK sources. We do not run a lab and we do not invent test scores.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources checked for this comparison, plus the amazon.co.uk listing facts in the display file on 16 October 2026. Shelf prices and star lines are those UK figures. The Ofgem unit rate is the Direct Debit average for England, Scotland and Wales, not a Northern Ireland tariff and not a measured bill.
This page contains affiliate links to amazon.co.uk. If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are from the UK listings checked on 16 October 2026. We did not lab-test these seedling heat mats.
