Best Industrial Cannon Space Heaters UK 2026: Diesel & Propane Picks
Our pick of the best industrial cannon space heaters for UK workshops, barns and building sites in 2026, from the JCB-SH70D diesel heater to the Clarke Devil propane range, plus how to size one and use it safely.
Key takeaways
- "Cannon heater", "torpedo heater", "jet heater" and "space heater" all describe the same thing: a portable, fan-assisted burner that blasts hot air out of a tube.
- Prices checked at jcb-tools.co.uk and machinemart.co.uk on 26 October 2026 and include VAT.
- JCB lists a 19-litre tank and 1.9 litres an hour at full output, which works out at roughly ten hours of continuous running per fill.
- My rule of thumb: if the heater is going to sit in one big, drafty building and run for hours, go diesel with a thermostat.
- Output is listed in kilowatts (kW) or BTU per hour (1kW is roughly 3,412 BTU).
Quick Answer
The best industrial cannon space heater for most UK workshops, barns and farm buildings is the JCB-SH70D (20kW diesel/kerosene, 496m³, thermostat, £251.99). If you'd rather run propane, the Clarke Devil 900 (17.6–24.9kW, 6.4kg, around £198) is the lightest serious all-rounder, and the Clarke DEVIL1600DV is the pick for building sites because it runs on 110V. For very large sheds and warehouses, step up to the JCB-SH215D (63kW) or Clarke Devil 4000 (up to 117kW). Every heater on this list is direct-fired: it puts combustion gases into the space, so it needs real ventilation and should never be used in a home or occupied living area.
By Jim Fellows, Garden Machinery Specialist, Garden-Review
Updated October 2026. Jim covers outdoor power and site equipment for Garden-Review, from generators and water pumps to the kit that keeps workshops usable through a British winter.
How we put this guide together: We compared manufacturer specifications, published fuel-consumption figures, warranty terms and current UK retail prices (checked 26 October 2026), and cross-referenced safety guidance from the HSE, NHS and Liquid Gas UK. Garden-Review earns commission if you buy through some links (JCB Tools and Machine Mart are affiliate partners). That never changes which heater we recommend for which job.
What Is a Cannon Heater?
"Cannon heater", "torpedo heater", "jet heater" and "space heater" all describe the same thing: a portable, fan-assisted burner that blasts hot air out of a tube. They're built to take a cold, draughty building from miserable to workable in minutes, which is why you'll find them in MOT bays, lambing sheds, marquees, garden workshops and half-built extensions all over the country.
There are two main fuel families in the UK:
- Diesel / kerosene (paraffin) cannons carry their own fuel tank on board, roll around on wheels, and usually have a thermostat. They're the classic big-barn, big-shed heater. The JCB range is in this camp.
- Propane cannons connect to an external propane cylinder by hose and regulator. They're dramatically lighter (the Clarke Devil 900 weighs 6.4kg against 16.5kg for the smallest JCB) and quieter on fumes, but you're juggling gas bottles. The Clarke Devil and SIP Fireball ranges at Machine Mart are propane.
Both types still need a 230V (or 110V) supply to run the fan and ignition, unless you buy a battery model like the SIP Fireball 515.
Best Industrial Cannon Space Heaters UK 2026: At a Glance
| Heater | Best for | Fuel | Output | Coverage | Price |
|---|---|---|---|---|---|
| JCB-SH70D | Best overall | Diesel / kerosene | 20kW | 496m³ | £251.99 |
| Clarke Devil 900 | Best propane all-rounder | Propane | 17.6–24.9kW | Medium workshops | £197.99 |
| Clarke DEVIL1600DV | Best for building sites (110V) | Propane | 22–36.6kW | Large workshops | £238.80 |
| JCB-SH140D | Best mid-size diesel | Diesel / kerosene | 37kW | 800m³ | £304.00 |
| JCB-SH215D | Best for barns & big sheds | Diesel / kerosene | 63kW | 1300m³ | £367.00 |
| Clarke Devil 500 | Best budget | Propane | 10kW | Small garages | £93.59 |
| SIP Fireball 515 | Best cordless | Propane + 18V battery | 15kW | 345m³ | £239.00 |
| Clarke Devil 4000 | Best for warehouses | Propane | 70–117kW | Very large spaces | £586.80 |
Prices checked at jcb-tools.co.uk and machinemart.co.uk on 26 October 2026 and include VAT. Coverage figures are the manufacturers' own where published.
The Best Industrial Cannon Heaters, Reviewed
1. JCB-SH70D 20kW Diesel Space Heater: Best Overall
Price: £251.99 | Fuel: diesel or kerosene | Output: 20kW (68,243 BTU) | Coverage: up to 496m³ | Tank: 19L | Burn rate: 1.9L/hr | Weight: 16.5kg | Warranty: 3 years (1 year commercial)
For a typical double-garage workshop, a timber-framed barn or a polytunnel-sized shed, 20kW is the sweet spot, and the JCB-SH70D is the most complete package at this size I've found. JCB lists a 19-litre tank and 1.9 litres an hour at full output, which works out at roughly ten hours of continuous running per fill. In practice the thermostat will cycle the burner off once the space is up to temperature, so a tank should comfortably last a working day.
What sets it apart from cheaper no-name diesel cannons is the detail: a built-in thermostat with a display showing both room and machine temperature, a flame cone to throw heat where you want it, wheels and a rear handle, and a standard 13A plug. The three-year domestic warranty is the longest on this list (commercial users get one year), and it's backed by Genpower's UK service operation in Pembrokeshire.
Watch out for: at 84dB it's loud, as all diesel cannons are, and the max outlet temperature is listed at 393°C, so keep a generous clear zone in front of the nozzle. Who it's for: farm buildings, garden workshops, agricultural sheds, small commercial units.
2. Clarke Devil 900 Propane Space Heater: Best Propane All-Rounder
Price: £197.99 (was £203.98) | Fuel: propane | Output: 17.6–24.9kW (60,000–85,000 BTU) | Gas use: 1.16–1.79kg/hr | Airflow: 535m³/hr | Weight: 6.4kg | Power: 230V, 110W
The Devil 900 has been a fixture of British garages for years, and it's easy to see why. At 6.4kg you can carry it one-handed from the van to the workshop, and the variable output lets you run it hard to warm up a cold space, then turn it down to save gas. It shuts off automatically if the flame fails, it overheats or the power drops, and it comes with the hose and regulator in the box.
You just add a propane cylinder. Propane burns noticeably cleaner than diesel, so in my view this is the better choice for anyone who's put off by the smell of a diesel cannon.
The trade-off is the bottle logistics: at full output it will empty a 19kg propane cylinder in roughly ten to eleven hours. Who it's for: home mechanics, woodworkers, small fabrication shops, anyone who moves their heater around a lot.
3. Clarke Devil 1600DV Dual Voltage: Best for Building Sites
Price: £238.80 | Fuel: propane | Output: 22–36.6kW (75,000–125,000 BTU) | Gas use: 1.59–2.63kg/hr | Airflow: 580m³/hr | Power: 110V or 230V
On most UK construction sites, 230V tools are off the table and everything runs from a yellow 110V transformer. That's what the "DV" models are for: the DEVIL1600DV runs on either voltage and ships with a 13A plug for workshop use. With up to 36.6kW on tap it will take the chill off a sizeable site cabin, an unheated new-build shell or a large workshop, and like the rest of the Devil family it has flame-failure, overheat and power-loss cut-outs.
If you need a little less heat, the DEVIL900DV (24.9kW, £203.98) is the same idea in a smaller size, and the DEVIL2100DV (50kW, £346.80) goes bigger. Who it's for: builders, plasterers (drying and curing), groundworkers, contractors working under site 110V rules.
4. JCB-SH140D 37kW Diesel Space Heater: Best Mid-Size Diesel
Price: £304.00 | Fuel: diesel or kerosene | Output: 37kW (126,250 BTU) | Coverage: up to 800m³ | Tank: 38L | Burn rate: 3.8L/hr | Weight: 22.3kg | Warranty: 3 years (1 year commercial)
The SH140D gives you almost double the SH70D's output for about £50 more, with a 38-litre tank that again runs for roughly ten hours flat out. It's the size I'd point most people towards for a steel-portal farm building, a two-bay commercial garage or a large outbuilding with poor insulation, where a 20kW unit would run flat-out all day and still struggle. Same thermostat, flame cone, wheel kit and 13A plug as its smaller sibling.
Availability note: at the time of writing this model is on pre-order at JCB Tools, with shipping after 19 November 2026. If you need heat before then, the SH70D is in stock now.
5. JCB-SH215D 63kW Diesel Space Heater: Best for Barns and Big Sheds
Price: £367.00 | Fuel: diesel or kerosene | Output: 63kW (215,000 BTU) | Coverage: up to 1,300m³ | Tank: 50L | Burn rate: 5.8L/hr | Weight: 26kg | Warranty: 3 years (1 year commercial)
This is the heavy hitter of the JCB range, and for the money it's very strong value: 63kW for under £370 works out at under £6 per kilowatt, the best value of any diesel heater in this guide (only the much bigger Clarke Devil 4000 comes in cheaper per kW). The 50-litre tank gives around eight and a half hours at full power. It's the one for agricultural buildings, event marquees, large workshops and warehouse corners. The outlet runs very hot (JCB quotes a maximum of 516°C), so plan your positioning carefully and keep combustibles, straw and fuel cans well away from the business end.
Availability note: pre-order, shipping after 19 November 2026.
6. Clarke Devil 500 10kW Propane Heater: Best Budget Pick
Price: £93.59 | Fuel: propane | Output: 10kW fixed (34,121 BTU) | Gas use: 0.704kg/hr | Airflow: 170m³/hr | Weight: 4.2kg | Power: 230V, 35W
Not everyone needs 20kW. For a single garage, a shed workshop or a potting shed you use at weekends, the Devil 500 delivers a steady 10kW from a package that weighs just over 4kg.
]There's no variable control, but it has piezo ignition plus the same flame-failure, overheat and power-loss shut-offs as its bigger brothers. At 0.7kg of gas an hour it's also the cheapest heater here to run. The Devil 600 (15kW fixed, £119.70) is the step up if your space is a bit bigger.
7. SIP Fireball 515 Cordless Propane Heater: Best Cordless
Price: £239.00 | Fuel: propane | Output: 15kW (51,182 BTU) | Coverage: approx. 345m³ | Power: 18V 5.2Ah battery (included) | Runtime: up to approx. 8 hours per charge | Warranty: 2 years
Every other heater here needs a socket. The Fireball 515 runs its fan and ignition from an 18V battery, which makes it uniquely useful on allotments, in field shelters, stables, remote outbuildings and early-stage sites with no power yet. SIP quotes up to eight hours from a charge, and the battery, charger, hose and regulator are all in the box. Fifteen kilowatts is plenty for a medium workshop or a stable block.
8. Clarke Devil 4000 117kW Propane Heater: Best for Warehouses
Price: £586.80 | Fuel: propane | Output: 70–117kW (250,000–400,000 BTU) | Power: 230V
When the space is measured in hundreds of square metres, you need something like the Devil 4000. It's the most powerful heater in this round-up, adjustable between 70kW and 117kW, and built for warehouses, large industrial units and event spaces. At this output you'll want a manifold of large propane cylinders or a bulk supply, and you should get your ventilation and gas arrangements properly assessed. In between, the Devil 2100 (35.2–49.8kW, £299.98) and Devil 3000 (82kW, £454.80) fill the gap.
Diesel vs Propane Cannon Heaters: Which Should You Buy?
| Diesel / kerosene (e.g. JCB) | Propane (e.g. Clarke Devil) | |
|---|---|---|
| Weight | 16–26kg, on wheels | 4–8kg, carry handle |
| Fuel handling | On-board tank, refill from a can | External cylinder and hose |
| Fumes and smell | Stronger, noticeable odour | Cleaner burn, less odour |
| Thermostat | Built in on the JCB range | Usually manual variable output |
| Best suited to | Barns, large sheds, long static runs | Workshops, sites, moving between jobs |
| Watch out for | Very hot outlet, noise, fuel spills | Cylinder storage and changeover rules |
My rule of thumb: if the heater is going to sit in one big, drafty building and run for hours, go diesel with a thermostat. If you move it around, work in smaller spaces, or you're sensitive to fumes, go propane.
What Size Cannon Heater Do You Need?
Output is listed in kilowatts (kW) or BTU per hour (1kW is roughly 3,412 BTU). To size a heater, start with the volume of the space: length × width × height in metres. Then use the guide figures JCB publishes on its space-heater buying page:
- Well-insulated building: about 35–50 watts per cubic metre
- Uninsulated steel or timber building: about 60–80 watts per cubic metre
Worked example
A 10m × 6m uninsulated timber workshop with a 3m ceiling is 180m³. At 60–80W per m³ you need roughly 11–14kW. A 10kW Devil 500 would struggle on a frosty morning; a 15kW Fireball 515 or a 20kW JCB-SH70D running on its thermostat would be comfortable.
If in doubt, size up slightly and turn it down. A heater running flat out all day in an undersized role wastes fuel and never quite gets the space warm.
Safety: Ventilation, Carbon Monoxide and Gas Bottles
This is the part that matters most, so please read it before you buy anything. Every cannon heater on this list is direct-fired. There's no flue. All the exhaust from the burner (water vapour, carbon dioxide and potentially carbon monoxide) goes straight into the space you're heating.
- Ventilate properly. JCB's own guidance says its diesel heaters are only suitable for very well-ventilated buildings or short-duration use, and must never be used in occupied living spaces. Leave doors or vents open. Don't seal up a workshop and run a cannon all day.
- Fit a CO alarm. The NHS warns that carbon monoxide has no smell or taste, and that a tension-type headache is the most common symptom of mild poisoning. If you feel better when you step outside, or others in the workshop have the same symptoms, switch off, get into fresh air and seek medical advice.
- Never use these heaters in a house, caravan, tent or attached garage that shares air with living areas.
- Store propane cylinders outdoors. Liquid Gas UK, the industry trade association, stresses that propane is an outdoor gas. Its chief executive George Webb puts it simply: knowing which cylinder to use and "following proper safety guidelines is crucial". Keep spare bottles outside, upright and away from drains, and change cylinders in the open air.
- Keep a clear zone. Outlet temperatures run from about 390°C to over 500°C on the JCB models. Keep sawdust, straw, fabrics, paint and fuel cans well clear of the nozzle.
- Never refuel a hot or running diesel heater, and use approved fuel cans for diesel and kerosene.
If you employ people, there's a legal side too. The HSE's Approved Code of Practice says indoor workplaces should normally be at least 16°C, or at least 13°C for physically demanding work. As HSE's John Rowe has put it, "Complying with the code of practice is the right thing for an employer to do." A cannon heater is often the quickest way to get there, but the heater itself must be part of your risk assessment.
Running Costs: What Does a Cannon Heater Cost Per Hour?
Running cost is simply fuel used per hour multiplied by what you pay for it. Using manufacturer figures at full output:
- JCB-SH70D: 1.9L of diesel or kerosene per hour
- JCB-SH140D: 3.8L per hour
- JCB-SH215D: 5.8L per hour
- Clarke Devil 500: 0.7kg of propane per hour
- Clarke Devil 900: 1.16–1.79kg of propane per hour
- Clarke DEVIL1600DV: 1.59–2.63kg of propane per hour
Multiply by your local price per litre or per kg of propane to get an hourly figure. Thermostat models will cycle off once the space is warm, so real-world costs are usually well below these peak numbers. Kerosene (heating oil / paraffin) is often cheaper than road diesel and burns slightly cleaner in the JCB units.
How We Chose These Heaters
We started with the full JCB Tools space-heater range and Machine Mart's gas-fired space-heater category, then compared every model on output, coverage, fuel consumption, weight, safety cut-outs, power options (230V, 110V, battery), warranty and price per kW. We picked the strongest option for each common job rather than simply the biggest numbers, and we've flagged stock and pre-order status where it affects what you can actually buy this winter.
Related Guides on Garden-Review
- Clarke Space Heater Buying Guide: a deeper dive into the full Clarke range
- Best Garage Heater UK 2026: electric and gas options for smaller garages
- Oil Filled Radiator vs Convector vs Fan Heater: if you need safer, flue-free heat for occupied rooms
- Best Inverter Generator Picks for the UK: power a cannon heater's fan where there's no mains
- Best JCB Tools for Landscapers and Gardeners
- All JCB Tools coverage
Sources and Further Reading
Frequently Asked Questions
What is the best industrial space heater in the UK?
Can you use a diesel space heater indoors?
Is propane or diesel cheaper to run?
What size space heater do I need for a garage?
Do I need a 110V space heater for a building site?
Can JCB space heaters run on kerosene?
Are cannon heaters safe to leave unattended?
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