For a campervan, Webasto, Eberspächer and Autoterm all make diesel air heaters of around 2 kW that draw between 0.1 and 0.28 litres of fuel an hour from the vehicle’s tank, according to their spec sheets. Their figures are close, and each diesel heater in that size targets the same job. The installation matters more than the brand: combustion air must come from outside, exhaust must go outside, and a carbon monoxide alarm belongs in the living space.
1. Start with the 2 kW models, and look at 4 kW if your van’s volume or climate calls for it.
2. Combustion air intake and exhaust outside the vehicle, never in the living area or a locker.
3. A carbon monoxide alarm designed for leisure vehicles, tested regularly.
How a diesel heater works
Every maker uses the same principle: a burner heats an exchanger, a fan blows cabin air across it, and the warm air returns to the van through ducting. Combustion takes place in a separate circuit that draws air from outside and vents it outside. A small dosing pump lifts fuel from the vehicle’s main tank.
That sealed circuit is what makes a diesel heater so well suited to a van: combustion does not release water vapour inside, unlike a portable gas heater. Our article on campervan condensation explains why that matters so much in winter.
Comparing 2 kW diesel heaters
Manufacturer spec sheets let you compare the three most common models in this size. The figures come from different documents and are not measured under the same conditions, so treat them as a guide.
| Model | Heat output | Fuel | Power draw | Source |
|---|---|---|---|---|
| Webasto Air Top 2000 STC | 0.9 to 2.0 kW | 0.12 to 0.24 l/h | 14 to 29 W | Webasto brochure, 2022 |
| Eberspächer Airtronic S2 D2L | 0.9 to 2.2 kW | 0.28 l/h | 34 W | Eberspächer sheet, 2018 (Commercial version) |
| Autoterm Air 2D | 0.8 to 2 kW | 0.10 to 0.24 l/h | 10 to 29 W | Autoterm website |
For larger vans or harsh winters, Autoterm rates its Air 4D at 1 to 4 kW, 0.12 to 0.51 l/h of fuel and 10 to 57 W of electrical draw. Eberspächer has replaced the Airtronic S2 with the Airtronic S3 Commercial D2L, listed in its motorhome brochure at 0.85 to 2.2 kW, 0.1 to 0.28 l/h and 6 to 28 W.
On price, UK dealer West Wilts Campers listed a 2 kW Autoterm Air 2D kit at £625 including VAT on 13 October 2026, with the PU-05 controller adding £110 and professional fitting available from £600 plus VAT. Yachting Monthly’s 2021 test of the Eberspächer S2 D2L quoted from £895 for the heater and £2,290 for a fitted kit. Always check what a kit includes before comparing offers.
What a diesel heater uses overnight
A heater also draws on your leisure battery, for its fan, fuel pump and ignition. Here is a worked example to redo with your own model’s spec sheet and your own heating time. Take an Autoterm Air 2D at full power for 8 hours.
| Step | Calculation | Result |
|---|---|---|
| Fuel at full power | 0.24 l/h × 8 h | 1.92 l |
| Electricity at full power | 29 W × 8 h | 232 Wh |
| In amp hours at 12 V | 232 Wh ÷ 12 V | about 19 Ah |
In practice a diesel heater turns itself down once the cabin reaches temperature, so real consumption falls between the minimum and maximum on the sheet. Add this line to your power budget when you size your van battery bank, and keep a safety margin.
Fitting a diesel heater safely
The installation manual for Autoterm Air heaters sets clear rules. Combustion air must not be taken from the interior, living space, engine bay or luggage compartment. The intake pipe must not exceed 2 metres, and the heater must never run without it. If the intake and exhaust sit on the same side, they need enough distance between them to stop exhaust being drawn back in, at least 20 cm.
According to the same manual the exhaust pipe can reach 500 °C. It runs through flexible metal pipe no longer than 2 metres, pointing downwards and protected from snow and mud, and exhaust gases must be removed outside the vehicle. Autoterm also forbids running the heater in closed or unventilated places such as a garage or workshop.
Wire it to the leisure battery on its own fuse, and fit it into your campervan wiring diagram. If you fit it yourself, have the installation checked: a badly fitted heater is a direct source of carbon monoxide.
Carbon monoxide alarms and winter fuel
The National Caravan Council urges campervan users to regularly test and maintain their carbon monoxide alarm, and warns that portable gas heaters designed for outdoor use must never be used inside a campervan. BSI’s guidance on carbon monoxide detection points motorhomes and other leisure accommodation vehicles to the BS EN 50291-2 standard. Alarm maker FireAngel recommends a unit certified to EN 50291, placed in the same room as the appliance at a horizontal distance of 1 to 3 metres, and tested monthly.
Cold also affects the fuel. If you head to the French Alps, TotalEnergies defines the cold filter plugging point, or TLF in French, as the lowest temperature at which diesel still passes through a calibrated filter, and gives -15 °C for standard winter diesel against -21 °C for its Excellium Grand Froid. Your diesel heater draws from the same tank as the engine, so fill up with cold-weather diesel before heading into serious cold.
Altitude changes combustion too. Autoterm’s website now lists a maximum working altitude of 4,200 m with a high-altitude sensor for the Air 2D, while its 2021 manual gave 2,500 m, and Eberspächer quotes automatic altitude adjustment up to 3,000 m for the Airtronic S2. Check the sheet for your exact version before a trip to the high mountains.
Your shortlist: which diesel heater for your van
| Use | Our advice |
|---|---|
| Spring and autumn weekends | 2 kW diesel heater, mid-sized leisure battery |
| Regular winter trips | Well-insulated van with a 2 kW heater, CO alarm, winter diesel in the mountains |
| Full-time living, large van, deep cold | 4 kW or 2 kW depending on insulation, altitude sensor, power budget redone |
Start with a properly fitted 2 kW diesel heater and work on insulation at the same time: the more heat your walls leak, the longer the heater runs at full power. Our comparison of cork and Armaflex insulation helps you tackle that before winter.