Best diesel heater for a camper van: seven units compared on minimum output, draw, weight and price
· 13 min read
For most insulated vans up to about 6 m the right heater is a 2 kW unit that idles below 1 kW, and on the spec sheets the Autoterm Air 2D does that for half the price of the Webasto and Eberspächer it copies in size; a long or ducted van wants the Autoterm Air 4D; a full-timer who also wants hot water is buying a Truma Combi D 6 and a bay to put it in. That is the short version of a spec-sheet comparison of seven diesel heaters ranked on the numbers that decide whether one suits a van: minimum output (the one that stops it cycling), maximum output, peak electrical draw, weight, case volume and price.
I have not run these side by side; the method box says what I did. The layout part is what this guide adds: every unit is a planner preset or a case size you can drop under a seat or a bed in VanPlot to see whether the exhaust run and the fuel pickup land where the floor allows.
Best overall
Autoterm Air 2D
Idles at 0.8 kW, 3.0 kg, same case as the German units, half their price.
Overall 8.2 / 10 · 3 kg · ≈ €480
Best premium 2 kW
Webasto Air Top 2000 STC
Lightest unit here at 2.6 kg and the widest dealer network; petrol version available.
Overall 7.7 / 10 · 2.6 kg · ≈ €1,000
Best budget (read the caveats)
VEVOR 5 kW all-in-one
≈ €90 with tank and controller — but no published idle or draw, and the tank must live outside the cabin.
Overall 7.3 / 10 · 9.6 kg · ≈ €92
Best for long vans
Autoterm Air 4D
4 kW with a 1.0 kW floor for the price of a 2 kW German unit.
Overall 6.6 / 10 · 5.5 kg · ≈ €555
Best if you want hot water too
Truma Combi D 6
6 kW ducted heat and 10 L of hot water from one burner; 16.9 kg and a real bay.
Overall 2.1 / 10 · 16.9 kg · ≈ €2,790
The comparison
| # | Product | Overall | Minimum output | Maximum output | Peak running draw | Weight | Case volume | Price | Fuel and draw (as reported) | W × H × D | Weight | Price |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Autoterm Air 2D Best overall 2 kW air heater | 8.2 | 0.8 kW 10.0 | 2.0 kW 0.0 | 29 W 10.0 | 3.0 kg 9.7 | 4.4 L 10.0 | €480 8.6 | 0.10–0.24 l/h; 10–29 W running (Autoterm) | 310 × 120 × 119 mm | 3 kg | ≈ €480 |
| 2 | Webasto Air Top 2000 STC Best premium 2 kW 2 kW air heater | 7.7 | 0.9 kW 9.2 | 2.0 kW 0.0 | 29 W 10.0 | 2.6 kg 10.0 | 4.5 L 10.0 | €1,000 6.6 | 0.11–0.23 l/h; 13–30 W running (Webasto) | 311 × 121 × 120 mm | 2.6 kg | ≈ €1,000 |
| 3 | Eberspächer Airtronic S2 D2L 2.2 kW air heater | 7.6 | 0.8 kW 9.6 | 2.2 kW 0.5 | 31 W 9.4 | 2.7 kg 9.9 | 4.3 L 10.0 | €1,100 6.3 | 0.10–0.28 l/h; 4–31 W running, ≤ 100 W at start (Eberspächer) | 310 × 115 × 122 mm | 2.7 kg | ≈ €1,100 |
| 4 | VEVOR 5 kW all-in-one Best budget (read the caveats) 5 kW air heater with integral tank | 7.3 | n/p — | 5.0 kW 7.5 | n/p — | 9.6 kg 5.1 | 32.4 L 5.8 | €92 10.0 | 0.18–0.48 l/h (VEVOR); minimum output and electrical draw not published | 409 × 312 × 254 mm | 9.6 kg | ≈ €92 |
| 5 | Autoterm Air 4D Best for long vans 4 kW air heater | 6.6 | 1.0 kW 8.3 | 4.0 kW 5.0 | 62 W 0.0 | 5.5 kg 8.0 | 11.9 L 8.9 | €555 8.3 | 0.12–0.51 l/h; 10–62 W running (Autoterm) | 402 × 188 × 157 mm | 5.5 kg | ≈ €555 |
| 6 | Webasto Air Top EVO 40 4 kW air heater | 5.4 | 1.5 kW 4.2 | 4.0 kW 5.0 | 55 W 2.1 | 5.9 kg 7.7 | 10.1 L 9.1 | €1,530 4.7 | 0.18–0.49 l/h; 15–55 W running (Webasto) | 423 × 162 × 148 mm | 5.9 kg | ≈ €1,530 |
| 7 | Truma Combi D 6 Best if you want hot water too 6 kW combi: air + 10 L water heater | 2.1 | 2.0 kW 0.0 | 6.0 kW 10.0 | 48 W 4.2 | 16.9 kg 0.0 | 70.9 L 0.0 | €2,790 0.0 | 0.22–0.63 l/h (110 ml/h at 1 kW average); 1.8–4 A at 12 V (Truma) | 525 × 300 × 450 mm | 16.9 kg | ≈ €2,790 |
How these are rated — and what I did not do
I have not run these units side by side. This is a spec-sheet comparison: every number in the table is a manufacturer or retailer figure, linked per product and checked September 2026. Where makers publish energy figures under different conditions they are shown as reported and kept out of the score, because a number measured at 32 °C cannot be ranked against one measured at 25 °C. What can be ranked fairly is arithmetic on published dimensions, weight, capacity and price — the things that decide whether a unit fits your layout, what it costs you in payload, and what it costs per litre. That is what the score is.
Each metric is scaled 0–10 across this set (best = 10, worst = 0), then weighted:
- Minimum output — 20 % (lower is better)
- Maximum output — 15 % (higher is better)
- Peak running draw — 15 % (lower is better)
- Weight — 15 % (lower is better)
- Case volume — 15 % (lower is better)
- Price — 20 % (lower is better)
- Outputs, fuel and electrical figures are the makers' published ranges (control range, not boost).
- Prices are the planner's EU street presets (August 2026) or the retailer listing named under each product; kit prices include a controller, unit-only prices do not — the note says which. GBP × 1.17, USD × 0.92.
- The Truma Combi D 6 is a combined air and water heater; it is ranked on heater metrics only, which is why it scores last and still carries an award.
- n/p = not published; the VEVOR's missing minimum output and current draw are left out of its score, not zeroed — read its verdict before reading its rank.
No affiliate links: product links go to the manufacturer or the spec page the numbers came from. If a spec here is wrong, tell me and I will fix it and note the change.
How to choose: minimum output first, then the hole in the floor
Size to the minimum, not the maximum. A well-insulated L2 or L3 van needs about 1 kW to hold 20 °C at freezing outside; a heater whose lowest setting is 1.5 kW cycles on and off and the cabin swings with it. That is why the 2 kW class wins the table for most vans, and why the minimum-output column carries the highest weight. The 4 kW class earns its place in a 7 m van, an uninsulated one, or a ducted layout with a bathroom and a rear bed both wanting outlets.
The install is the spatial decision. Every unit here needs a flat floor panel, an exhaust route to the outside and a fuel pickup — the standpipe into the van’s own tank on most builds. The 2 kW cases are identical in size, so the choice between them is price and dealer, not packaging. The Truma Combi D 6 is a different object: a 16.9 kg cabinet that also holds 10 L of hot water, which replaces a separate calorifier and its plumbing — the water post covers what that plumbing would otherwise be.
What it costs the battery is small: 10–30 W running, 10–20 Ah a night. The fridge is the bigger load; heating is a diesel cost, about a litre a night at 1 kW average. Insulation is what shrinks both — the insulation guide gives the centimetres it costs.
The heaters, in order
1. Autoterm Air 2DBest overall
Overall 8.2/10 · 310 × 120 × 119 mm (4.4 L outside) · 3 kg · ≈ €480 (EU street, planner preset, Aug 2026 (unit + basic controller)) · reported: 0.10–0.24 l/h; 10–29 W running (Autoterm)
The lowest idle in the guide (0.8 kW), the same 310 mm case as the German units, 3.0 kg, and half the price — the arithmetic puts it first and nothing in the spec sheets argues back. The gap to Webasto and Eberspächer is dealer density and name, not output or draw. For a self-installer with a 2 kW brief this is the default.
Reasons to buy
- Idles at 0.8 kW — low enough not to cycle in an insulated van
- Same 310 mm case and mounting pattern as the Webasto and Eberspächer 2 kW units
- Half the price of the German pair, with a European parts network
Reasons to avoid
- Fewer installers know it than Webasto/Eberspächer
- Altitude limit 4,200 m per spec; check the HA version if you need more
- Controller options are the price difference — budget for the Comfort Control
In the planner: pick Diesel heater and choose the preset “Autoterm Air 2D” — it drops in at these dimensions and this weight, so the fit and the axle load are checked before you order. Specs: autoterm.com, berger-camping.com.
2. Webasto Air Top 2000 STCBest premium 2 kW
Overall 7.7/10 · 311 × 121 × 120 mm (4.5 L outside) · 2.6 kg · ≈ €1,000 (EU street, planner preset, Aug 2026 (kit)) · reported: 0.11–0.23 l/h; 13–30 W running (Webasto)
Lightest heater here at 2.6 kg, the reference 2 kW unit every installer has fitted, a petrol version for petrol vans. It gives up a tenth of a kilowatt of idle to the Autoterm and Eberspächer and costs twice the Autoterm; you are paying for the network. A sound purchase, not a bargain.
Reasons to buy
- Lightest unit here at 2.6 kg
- Dealer network in every country; the reference 2 kW van heater
- Petrol version exists for petrol vans
Reasons to avoid
- Twice the Autoterm's price for the same output band
- Controller (SmarTemp / MultiControl) is a separate line item
- 0.9 kW minimum is slightly higher than the Autoterm and Eberspächer
In the planner: pick Diesel heater and choose the preset “Webasto Air Top 2000 STC” — it drops in at these dimensions and this weight, so the fit and the axle load are checked before you order. Specs: webasto.com, heatso.com.
3. Eberspächer Airtronic S2 D2L
Overall 7.6/10 · 310 × 115 × 122 mm (4.3 L outside) · 2.7 kg · ≈ €1,100 (EU street, planner preset, Aug 2026 (kit)) · reported: 0.10–0.28 l/h; 4–31 W running, ≤ 100 W at start (Eberspächer)
Highest output of the compact class (2.2 kW) and the lowest idle after the Autoterm, with a brushless motor and built-in altitude compensation. The most expensive 2 kW unit, and the 115 mm case is narrower on paper only. If the van sees mountains, the altitude handling is the reason to pick it over the Webasto.
Reasons to buy
- Highest output of the compact class (2.2 kW) at the lowest idle (0.85 kW)
- Brushless motor; automatic altitude compensation to ~3,000 m built in
- 5,000-hour service life stated
Reasons to avoid
- Most expensive 2 kW-class unit
- EasyStart controllers add cost
- Narrowest case (115 mm) but the same length — no packaging advantage in practice
In the planner: pick Diesel heater and choose the preset “Eberspächer Airtronic S2” — it drops in at these dimensions and this weight, so the fit and the axle load are checked before you order. Specs: butlertechnik.com, heatso.com.
4. VEVOR 5 kW all-in-oneBest budget (read the caveats)
Overall 7.3/10 · 409 × 312 × 254 mm (32.4 L outside) · 9.6 kg · ≈ €92 (US$77–116 eBay/Amazon, Sep 2026, ×0.92) · reported: 0.18–0.48 l/h (VEVOR); minimum output and electrical draw not published
It scores well because it is nearly free and the two numbers that would hurt it — minimum output and current draw — are not published. Treat the score as incomplete. The case for buying one is a shed, a workshop or a van where you will build the exhaust, fuel and CO-alarm installation the kit does not include; the case against is putting a fuel tank inside the living space, which no maker of the units above allows.
Reasons to buy
- A tenth of the price of the German units
- Arrives assembled with tank, pump and controller in one box
- 5 kW nominal — more than any van needs
Reasons to avoid
- An all-in-one puts the fuel tank inside the van: mount it outside or in a sealed locker, vented, never in the living space
- No published minimum output or current draw, so two metrics are unscored
- Combustion-air and exhaust routing are your problem — the safety of the install is in the routing, not the unit
Not a planner preset yet; place a generic item and type these dimensions and weight in. Specs: vevor.com, amazon.com.
5. Autoterm Air 4DBest for long vans
Overall 6.6/10 · 402 × 188 × 157 mm (11.9 L outside) · 5.5 kg · ≈ €555 (€554.58 svb24.com, unit + bracket, excl. shipping) · reported: 0.12–0.51 l/h; 10–62 W running (Autoterm)
Four kilowatts for the price of a German two, and a 1.0 kW floor that keeps it usable in a mid-size van on mild nights. It is 5.5 kg and 402 mm long, and its 62 W peak draw is double the small units. The right heater for an L4, a family layout or anything with ducting to two rooms.
Reasons to buy
- 4 kW for the price of a 2 kW German unit
- Idles at 1.0 kW, so it works in a mid-size van too
- 70–120 m³/h airflow moves heat down a long van
Reasons to avoid
- 5.5 kg and 402 mm long — needs a real mounting bay
- 62 W peak draw is double the 2 kW class
- Oversized for a well-insulated L2
Not a planner preset yet; place a generic item and type these dimensions and weight in. Specs: autoterm.com, svb24.com.
6. Webasto Air Top EVO 40
Overall 5.4/10 · 423 × 162 × 148 mm (10.1 L outside) · 5.9 kg · ≈ €1,530 (£1,308 webastomarine.co.uk vehicle kit, ×1.17) · reported: 0.18–0.49 l/h; 15–55 W running (Webasto)
The premium 4 kW unit, 20 mm longer than the Autoterm 4D and 0.4 kg heavier, with the highest minimum output in the guide: 1.5 kW is more than a small insulated van can absorb without cycling. In a 7 m van with a ducted bathroom it is the polished choice; below that, the Autoterm 4D does the job for a third of the price.
Reasons to buy
- 4 kW with boost, in a case only 20 mm longer than the Autoterm 4D
- Webasto dealer and warranty network
- Diesel and petrol versions
Reasons to avoid
- Highest minimum output in the guide (1.5 kW) — it will cycle in a small van
- Heaviest air heater here
- Kit price approaches a Truma Combi
Not a planner preset yet; place a generic item and type these dimensions and weight in. Specs: webasto.com, webastomarine.co.uk.
7. Truma Combi D 6Best if you want hot water too
Overall 2.1/10 · 525 × 300 × 450 mm (70.9 L outside) · 16.9 kg · ≈ €2,790 (EU street, planner preset, Aug 2026) · reported: 0.22–0.63 l/h (110 ml/h at 1 kW average); 1.8–4 A at 12 V (Truma)
Last in a table that scores heaters, because it is not only a heater: 16.9 kg and a 540 × 500 × 350 mm bay buy a 6 kW ducted furnace and a 10 L water heater from one burner and one floor penetration. Its 2 kW minimum is too much for a small van in spring. For an L4 full-timer who wants hot water without a second appliance, it replaces two things and earns its weight.
Reasons to buy
- Heats the van and 10 L of water from one diesel burner and one hole in the floor
- Ducted to four outlets; the only unit here sized for a 7 m van
- Truma service network across Europe
Reasons to avoid
- 16.9 kg and a 540 × 500 × 350 mm bay — it is a piece of furniture
- 2 kW minimum: too much for a small insulated van in shoulder season
- Three times the price of a 4 kW air heater plus a separate water heater
In the planner: pick Combi heater (air + water) and choose the preset “Truma Combi D6 (diesel)” — it drops in at these dimensions and this weight, so the fit and the axle load are checked before you order. Specs: truma.com, termosa.com.
FAQ
What size diesel heater does a camper van need?
A 2 kW unit heats an insulated van up to about 6 m; the number that matters more is the minimum output, because an oversized heater cycles on and off in a small space. Autoterm Air 2D idles at 0.8 kW, Eberspächer S2 D2L at 0.85 kW, Webasto Air Top 2000 STC at 0.9 kW. A 4 kW heater (Autoterm 4D from 1.0 kW, Webasto EVO 40 from 1.5 kW) is for long or poorly insulated vans; 5 kW all-in-ones are sold on the big number, not the small one.
How much diesel does a van heater use per night?
Makers quote 0.10–0.28 l/h for the 2 kW class and 0.12–0.51 l/h for 4 kW. At a realistic shoulder-season average of 1 kW, that is roughly 0.12 l/h — about 1.2 L over a ten-hour night, or a litre of the van's own tank. Truma states 110 ml/h at 1 kW average for the Combi D 6.
How much electricity does a diesel heater draw?
Running, 10–31 W for a 2 kW unit and up to 55–62 W for 4 kW — 1–5 A at 12 V. Starting draws a burst of up to 100 W for a minute or two while the glow plug runs. Over a night a 2 kW heater uses 10–20 Ah, less than a fridge.
Where does a diesel heater go in a van?
Through the floor, on a flat panel away from the tank crossmember and fuel lines, with the exhaust and combustion-air intake outside — under the driver or passenger seat, or under a bed platform near the rear. The 2 kW units share a 310 × 120 mm case, the 4 kW class is 370–425 mm long, and the Truma Combi D 6 needs a 540 × 500 × 350 mm bay. All-in-one units with an integral tank should not sit in the living space; mount them outside or in a sealed, vented locker.
Are the cheap Chinese diesel heaters safe?
The unit is a copy of the German design; the risk is the installation. A sealed combustion path (intake and exhaust outside, exhaust joints clamped, a CO alarm inside) is what makes any diesel heater safe, and the cheap kits leave that entirely to you. They also publish no minimum output or current draw, so you cannot size them properly. If you buy one, budget for a proper exhaust, a marine-grade fuel line and a CO alarm — that is where the price difference went.
