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How a diesel air heater works
The heater draws a small amount of diesel through a metering pump, burns it in a sealed combustion chamber with outside air, vents exhaust outside, and passes cabin air across a heat exchanger. The cabin air never mixes with combustion gases – as long as the unit and its seals are sound. That's why build quality and installation matter more than the price tag.
Carbon monoxide & fire. Any fuel-burning heater must have a sealed combustion system with exhaust routed outside, installed to the manufacturer's manual – ideally by a qualified installer. Fit a certified CO alarm in the living area and test it regularly. Never sleep in a van with a heater you haven't had checked.
What to compare
- Heat output range (kW): both the max and the minimum. A low minimum lets the heater tick over overnight instead of cycling.
- Electrical draw (W): highest during start-up (glow plug), low while running.
- Fuel consumption (L/h): at min and max.
- Altitude capability.
- Noise: fuel pump ticking and exhaust note – mounting and silencers help.
- Controller: thermostat mode, timer, app.
- Dealer network and parts.
The models
Autoterm Air 2D
Best for: Builders who want a branded heater with documentation and a dealer network at a mid-range level.
- Heat output
- 0.8–2.0 kW
- Fuel use
- about 0.24 L/h at max
- Power draw
- 10–29 W
- Voltage
- 12 V or 24 V
- Weight
- 3 kg
- Formerly sold as Planar 2D – check you are buying current, genuine stock
- Install exhaust and combustion intake to the manufacturer manual
Specs: manufacturer page, checked 2026-11-14. Based on manufacturer specs and public reviews – not a hands-on test.
Webasto Air Top 2000 STC
Best for: Reference point for a branded, dealer-installed heater; look at its successor for new builds.
- Heat output
- 0.9–2.0 kW (3,100–7,000 BTU/h)
- Fuel use
- 0.12–0.24 L/h
- Power draw
- 14–29 W
- Voltage
- 12 V or 24 V
- Weight
- 2.6 kg
- Status
- Production ended – successor: Air Top Pro 25 (per Webasto)
- Discontinued – check stock, parts and the successor model
- Dealer installation recommended and sometimes required for warranty
Specs: manufacturer page, checked 2026-11-14. Based on manufacturer specs and public reviews – not a hands-on test.
| Spec | Autoterm Air 2D | Webasto Air Top 2000 STC |
|---|---|---|
| Heat output | 0.8–2.0 kW | 0.9–2.0 kW (3,100–7,000 BTU/h) |
| Fuel use | about 0.24 L/h at max | 0.12–0.24 L/h |
| Power draw | 10–29 W | 14–29 W |
| Voltage | 12 V or 24 V | 12 V or 24 V |
| Weight | 3 kg | 2.6 kg |
| Status | — | Production ended – successor: Air Top Pro 25 (per Webasto) |
| Best for | Builders who want a branded heater with documentation and a dealer network at a mid-range level. | Reference point for a branded, dealer-installed heater; look at its successor for new builds. |
Source: manufacturers' product pages (linked on each product card), checked 2026-11-14. “—” = not published on the page.
Webasto states that the Air Top 2000 STC is no longer in production and names the Air Top Pro 25 as its successor – check that model for a new build. Eberspächer's Airtronic range is the other major branded option.
Branded vs generic heaters
Low-cost generic diesel heaters are hugely popular. Our Webasto vs Chinese diesel heater comparison sets out the trade-offs honestly.
Installation essentials
- Mount under the floor or in a sealed locker, as specified by the manufacturer.
- Exhaust exits away from doors, windows, the fridge vent and where you sleep.
- Fuel pickup from the tank via the correct standpipe – never improvised.
- Fit a certified carbon-monoxide alarm inside the living area and test it regularly.
- Have the installation done or checked by a qualified installer, and keep the paperwork for insurance and inspections.
Frequently asked questions
How big a diesel heater do I need for a van?
Most vans use units rated around 2 kW maximum. Larger vans, poor insulation or very cold climates can justify more, but an oversized heater will spend its time on low output, which can encourage carbon build-up.
Are diesel heaters safe in a van?
When installed correctly – sealed combustion chamber, exhaust routed outside away from openings, combustion air taken from outside, and a working CO alarm inside – they are widely used. Faulty installation is the main risk. We strongly recommend professional installation.
How much diesel does a heater use?
Manufacturers list figures such as 0.12–0.24 L/h for the Webasto Air Top 2000 STC and about 0.24 L/h at maximum for the Autoterm Air 2D. Actual use depends on the setting and how long it runs.
Do diesel heaters work at altitude?
Combustion changes with altitude. Some models have altitude kits or automatic compensation – check the manufacturer's guidance if you go into the mountains.
Spotted an outdated spec? Tell us.