Campervan Heater — 12V Diesel Night Heater for Van Conversions
A 2.5KW diesel air heater is the right size for almost every campervan conversion. It runs on the diesel already in your tank and burns 0.136–0.252 L/hr. That holds a VW T6-size van at room temperature all night on roughly one liter.
A campervan is a harder heating job than a big motorhome, not an easier one. You sleep 3 feet (1m) from the heater. The metal shell has almost no thermal mass, and there is nowhere to hide a ticking fuel pump.
Four decisions actually matter in a small van. What size to buy, where the unit goes, how you feed it fuel, and how to keep it quiet enough to sleep through.
- Size — 2.5KW for a T5, T6, Vito, Trafic or Custom build. 5KW only for high-roof long-wheelbase vans in hard winter.
- Fuel — 0.136–0.252 L/hr on the Apollo-V1, so 1 to 1.5 liters over an eight-hour night on low.
- Power — about 8A for the first 2–3 minutes while the glow plug heats, then 1.46–1.68A running.
- Noise — ~50dB at low. The part you hear at 2 a.m. is the fuel pump, not the heater.
- Install — two holes in the floor, one fuel tap, one fused 12V feed. Most owners do it themselves.
- Certification — the Apollo-V1 holds ECE R122 and R10 type approval. The numbers are on the certification records page.
What Size Campervan Heater You Need
For a VW T5, T6, Vito, Trafic, Vivaro or Transit Custom conversion, 2.5KW is the right size — provided the van is insulated. That last clause does more work than the van's size does.
Heater sizing is a heat-loss sum, not a guess from van length. Vehicle heating uses a K-value method that has been standard for decades:
A = surface area of the living space, 2(LW plus LH plus WH), in m²
K = insulation and sealing coefficient, W/(m²·K) — see the table below
ΔT = inside temperature minus outside temperature, in °C
V = interior volume in m³, n = air changes per hour
The second term is the heat you lose out of the vents. The first term is everything else.
The K value is the number that decides your heater
A well-insulated T6 needs 1,000W. The same van with thin insulation needs 2,550W. Nothing changed except how it was built. This is why two owners of identical vans give opposite advice about heater size.
| Build quality | K value | What it looks like |
|---|---|---|
| Well insulated, sealed | 1.5 | Full insulation to walls, floor, roof; sealed panel gaps; thermal window covers |
| Typical camper conversion | 2.3 | Insulated but with thermal bridges at ribs, doors and windows |
| Light insulation | 4.0 | Thin foam or carpet lining, unsealed gaps |
| Bare metal van | 8–12 | No lining. Any heater loses this fight |
Running the sum for common vans at 14°F (-10°C) outside and 68°F (20°C) inside, with one air change per hour:
| Van (interior L × W × H) | Well insulated K 1.5 | Typical K 2.3 | Light insulation K 4.0 |
|---|---|---|---|
| VW T5 / T6 / T6.1 SWB, Vito Compact 2.6 × 1.7 × 1.4 m | 1,000 W | 1,500 W | 2,550 W |
| T6.1 LWB, Vito Long, Trafic LWB 3.0 × 1.7 × 1.4 m | 1,150 W | 1,700 W | 2,900 W |
| Sprinter / Transit / Ducato L2H2 3.3 × 1.8 × 1.8 m | 1,450 W | 2,200 W | 3,700 W |
| L3H3 high roof 3.7 × 1.9 × 1.9 m | 1,750 W | 2,600 W | 4,400 W |
The 2.5KW Apollo-V1 covers every insulated van on this list. Two situations push you to the 5KW Apollo-V2: a high-roof long-wheelbase van, or insulation you know is thin.
One more check worth running. A typical T6 at -22°F (-30°C) needs about 2,500W — sitting right on the Apollo-V1's ceiling. If you winter in Scandinavia or the Alps rather than Wales, size up.
What happens when you oversize
An oversized heater in a small van spends its whole life at minimum burn, and minimum burn is where soot forms. Van owners report exactly this. A 5KW unit turns a small build into an oven at 20°F (-7°C), so they turn it down and leave it simmering.
A correctly sized unit behaves differently. It runs at a useful output, reaches temperature, and shuts down cleanly instead of idling for eight hours.
What the KW Number on a Budget Heater Actually Means
On cheap heaters the KW figure is a setting, not a size. The low-cost market runs on a small number of physical burners. Sellers change the fuel and air settings, print a different number, and list the same hardware at several power ratings.
The best-known case is the 8KW listing. A genuine 8KW burner would be roughly 1.5 times the size of a 5KW one, yet the "8KW" units look identical to the 5KW. They are 5KW hardware turned up, which is why we wrote a buying guide for Amazon and eBay diesel heaters about it.
The same trick runs downward, and that is the one that catches campervan buyers. A 5KW unit turned down and relabeled "2KW" is common, because far more 5KW units are made than true small burners.
Why a detuned 5KW is the wrong heater for a small van
What matters overnight is not maximum output but minimum output. A large burner cannot turn down as far as a small one, so in a well-insulated van it overshoots, cycles, and coke starts forming.
Our own numbers show the gap. The Apollo-V1 idles at 0.136 L/hr; the Apollo-V2 cannot go below 0.201 L/hr. That floor is 48% higher, and in a 4 m³ van it is the difference between holding temperature and cooking you out.
Three checks that expose a relabeled unit
Body length is the standard test. A true small burner is around 300mm long; a 5KW chassis is around 400mm. Two more numbers confirm it, and all three sit on any honest specification sheet.
| Check | Apollo-V1 (2.5KW) | Apollo-V2 (5KW) |
|---|---|---|
| Case size | 310 × 122 × 115mm | 380 × 140 × 138mm |
| Bare unit weight | 2.6kg (5.7 lbs) | 4.8kg |
| Hot air outlet diameter | 60mm | 75mm |
| Fuel burn, min to max | 0.136–0.252 L/hr | 0.201–0.475 L/hr |
| Output at boost | 2.5KW / 8,500 BTU | 4.7KW / 16,100 BTU |
If a listing says "2KW" but quotes a 380mm case, a 75mm outlet or a 4.8kg unit weight, it is a 5KW. Ask for those three numbers in writing before you pay.
Where the Heater Fits in a Campervan
A small van has five workable positions: bench seat base, under a fixed bed, wardrobe base, under a front seat, or underslung. Every one of them is a trade-off between noise, floor space and access.
| Position | Works because | Costs you |
|---|---|---|
| Bench seat or rock-and-roll bed base | Short duct run, warm air at floor level, easy access for servicing | Loses storage; the bed frame can amplify pump noise |
| Under a fixed rear bed | The 310 × 122 × 115mm case fits the void behind the wheel arch | Heat comes out at the far end of the van from where you sit |
| Wardrobe or cupboard base | Hidden, ducts easily to two outlets | Needs a dedicated intake path so it never draws cabin air |
| Under the driver's or passenger seat | Factory-style position on VW vans; short fuel run to the tank | Tight for the 8 in (20cm) clearance the unit needs |
| Underslung, outside the floor | Burner noise stays outside; no floor space lost inside | Road salt and stone damage; the fan noise still comes in through the duct |
Whichever you pick, plan the exhaust route before you drill. The pipe must slope downward the whole way from the heater to the outside. No flat sections, and no low points where water vapor can collect and freeze.
Left: keep 8 in (20cm) clear around the unit and 4 in (10cm) in front of the outlet. Right: everything for a standard install is in the box.
Feeding It Fuel: Van Tank or Separate Tank
In a diesel campervan, tap the vehicle tank with a standpipe — it is the safest method and it means you never carry a jerrycan. The line goes down through the tank cap, so no hole is made in the tank wall and there is nothing to leak.
Leave 3/4 in (2cm) between the pickup tip and the tank floor. Water and sediment settle at the bottom, and that gap keeps them out of your fuel filter. The Vvkb fuel standpipe is 24 in (60cm) long, which reaches the bottom of most van tanks.
Set the pickup so it stops drawing before the tank is empty. A heater that keeps running after the engine has nothing left is a bad night out.
A petrol campervan cannot run a diesel heater. If your van is gasoline, use the Apollo-G1 gasoline air heater instead. A separate diesel tank is the other option, and it is the normal choice on towed caravans.
The Noise You Will Actually Hear at 2 a.m.
The fan is not the problem — the fuel pump is. Every diesel heater on the market, cheap or expensive, uses a solenoid dosing pump that ticks once per fuel pulse. In a house that would be inaudible. In a van you sleep 3 feet (1m) from it.
The tick itself is small. What makes it loud is the surface you bolt the pump to. Mount it hard against a bed frame or a flat plywood panel and the panel works as a soundboard.
Four fixes that work
- Mount the pump on rubber, on its own bracket, never directly to the bed frame or a large flat panel.
- Break the vibration path with a short length of flexible hose either side of the pump. Rigid fuel line carries the pulse straight into the furniture.
- Keep the pump 2–3 feet (60–100cm) from the heater, with the outlet pointing upward. Closer raises fuel pressure and makes combustion rough; further and the flame goes unstable.
- Fit a free-flowing silencer. Vvkb uses a spiral exhaust that drops noise without adding baffles.
Underslung mounting is the other lever. It puts the burner outside, but owners who try it report the same trade. The pump tick disappears, and fan noise through the duct becomes the thing that keeps them awake. Inside the van, mounted properly, the Apollo-V1 runs at ~50dB on low.
Condensation: Why Sealed Combustion Keeps a Van Drier
A flueless gas heater puts about 4 liters of water into your van over an eight-hour night. A diesel air heater puts in none. That is chemistry, not marketing — burning 1kg of propane produces roughly 1.6kg of water vapor, and a flueless heater releases all of it indoors.
A diesel air heater keeps the two air paths completely separate. Combustion air comes in through its own pipe, burns in a sealed chamber, and leaves through the exhaust. Only clean heated air enters the van.
Be realistic about what that fixes. Two people breathing add roughly 0.7 liters of moisture over the same night, and cooking and wet gear add more. The heater removes the largest single source, not all of them.
Two things still catch people out. A mattress that sits tight against the bed base traps vapor underneath and turns damp — a slatted or ventilated base solves it. Condensation also forms whenever a surface drops to dew point. A van kept too cold overnight streams with water regardless of which heater you own.
Wiring a Campervan Heater Into a 12V System
Run the heater from the leisure battery, on its own fuse, never from the starter battery. A night heater that flattens the battery you need to drive home turns a cold morning into a recovery call.
The draw is modest. The glow plug pulls about 8A for the first 2–3 minutes, then the Apollo-V1 settles to 1.46–1.68A at 12V once the flame is established.
Use the supplied 4-meter flame-retardant harness at full length rather than splicing in thin cable, and keep the fuse at the battery end. The heater cuts out below roughly 11.5V to protect itself. Undersized cable can trigger that shutdown, which then looks like a heater fault instead of a wiring fault.
Mount the control panel away from the hot air outlet. The panel holds the thermostat that reads cabin temperature. Warm air blowing across it shuts the heater down early while the far end of the van stays cold.
Vvkb Campervan Heater Models
Two air heaters cover every van conversion. Pick by heated volume first, and by nothing else second.
Apollo-V1 — 2.5KW
- 2.5KW / 8,500 BTU at boost, five heat levels
- 0.136–0.252 L/hr, 1.46–1.68A at 12V
- 310 × 122 × 115mm, 2.6kg (5.7 lbs), 60mm outlet
- ~50dB at low setting
- Rated to -40°F (-40°C), normal operation to 11,483 ft (3,500 m)
- Kyocera ceramic glow plug, 4-meter harness
- ECE R122 and R10 type approval, plus CE, RoHS and FCC
Apollo-V2 — 5KW
- 5KW rated — 4.7KW / 16,100 BTU measured at boost
- 0.201–0.475 L/hr, 1.93–2.2A at 12V
- 380 × 140 × 138mm, 4.8kg, 75mm outlet
- Five heat levels plus a 99-hour programmable timer
- 2520 stainless combustion chamber, holds shape at 1,200°C
- Rated to -40°F (-40°C)
- CE, RoHS and FCC documentation
The type approval numbers on the Apollo-V1 are E24*122R00/06*0054*00 and E24*10R06/02*4825*00, issued by NSAI in Ireland. Ask any seller for their approval number rather than a logo. A factory answers in one message.
What Campervan Owners Complain About
Three of the complaints are specific to small vans, and the install is where all three get decided. None of them are reasons not to fit one, but you should know them before you cut the floor.
- It is permanent. The install puts two holes through the van floor. On a leased or finance-return van, check the terms before you drill.
- The pump ticks. Mounting on rubber fixes most of it, but no diesel heater on any brand is silent.
- Floor space is the real cost. The unit plus its 8 in (20cm) clearance takes a locker you were probably counting on for storage.
- Fit a CO alarm. A sealed system vents outside, but an exhaust joint can loosen. An alarm costs less than one night's fuel.
Four more issues apply to every diesel heater in every vehicle. Soot from low-output running, the annual chamber clean, never cutting the power mid-cycle, and winter fuel gelling. All four are covered on the RV diesel heater page.
Frequently Asked Questions
What size diesel heater do I need for a campervan?
2.5KW for an insulated small van. A T6-size conversion needs 1,000W when well insulated and 2,550W with thin insulation, at 14°F (-10°C) outside. Insulation moves the answer more than van size does. Go to 5KW for a high-roof long-wheelbase van, thin insulation, or alpine winters.
Is a 2KW diesel heater enough for a VW T5 or T6?
Yes, if the van is insulated. A T5 or T6 SWB conversion needs about 1,500W at 14°F (-10°C) with typical insulation, so a 2.5KW unit has roughly 60% headroom. With only a thin foam lining the same van needs 2,550W, which leaves almost nothing spare.
Is an 8KW diesel heater better for a campervan?
No, and cheap 8KW heaters are not really 8KW. A genuine 8KW burner would be roughly 1.5 times the size of a 5KW one. Budget "8KW" units are the same chassis with the fuel turned up. Even at face value it is three times more heat than a converted small van can use.
Where is the best place to mount a diesel heater in a campervan?
Under a bench seat or the rock-and-roll bed base, in most builds. It keeps the duct run short and puts warm air at floor level. You need 8 in (20cm) of clearance around the unit and 4 in (10cm) in front of the outlet. The exhaust route must slope downward the entire way out.
Why does my campervan diesel heater tick?
That is the fuel dosing pump, and it is normal on every brand. A solenoid fires once per fuel pulse. It gets loud when the pump is bolted to a large flat surface that acts as a soundboard. Mount it on rubber, on its own bracket, with flexible hose either side of it.
Do diesel heaters cause condensation in a campervan?
No. A diesel air heater burns in a sealed chamber and sends every combustion product out of the exhaust, so it adds no moisture indoors. A flueless gas heater adds roughly 4 liters of water over an eight-hour night. Your remaining moisture sources are breathing, cooking and wet gear.
Can I fit a diesel heater to a petrol campervan?
Not to the vehicle tank. Diesel and gasoline heaters use different burners and are not interchangeable. On a petrol van, either fit the Apollo-G1 gasoline heater, which taps the existing tank, or run a diesel heater from its own small tank.
How much diesel does a campervan heater use overnight?
About 1 to 1.5 liters over eight hours on an Apollo-V1 at a low setting. The full range is 0.136–0.252 L/hr. A 5KW Apollo-V2 uses 0.201–0.475 L/hr, which is one reason oversizing costs you twice.
Should I mount a campervan heater underslung or inside the van?
Inside, for most conversions. Underslung mounting moves the burner noise outside and frees a locker, but it exposes the unit to road salt and stone damage. Owners who fit it underslung also report that fan noise still travels in through the duct, so the van does not end up much quieter.
Talk to the People Who Build It
Vvkb has manufactured vehicle heaters in China since 1996 and diesel heaters since 2003. You are dealing with the factory. Questions about ducting a specific van layout, or about an approval number, get answered by someone who can open the drawing.
Related Pages
- RV diesel heater — running costs against propane, battery maths and the full buying guide
- Van heater — Sprinter, Transit and ProMaster conversions
- Diesel heaters for caravans — towed caravans with no engine to draw fuel from
- Diesel heaters for motorhomes — larger coachbuilt vehicles and hydronic systems
- How to install a diesel heater — the full step-by-step with measurements
- Is a diesel heater safe to sleep with — sealed combustion, CO risk and alarms
