A diesel heater solves a very specific campervan problem: keeping the van warm when there is no electric hook-up and the leisure battery is far too valuable to waste on electric space heating. Once fitted properly, it can give you dependable overnight heat from a relatively small amount of fuel and 12V power.

The important questions come before you drill the first hole. A compact van may be better served by a genuine 2kW heater than an oversized 5kW unit, installation quality matters as much as the heater itself, and the difference between a lower-priced marketplace kit and a manufacturer-backed system is often support, documentation and parts rather than simply heat output. This guide covers those choices, running costs and fitting difficulty without turning into a step-by-step fuel-and-exhaust installation manual.

2kW or 5kW diesel heater: which should you choose?

Do not start with the idea that bigger must be better. A heater has to replace the heat your van is losing, and that depends on much more than the badge on the back door. Insulation, glass area, permanent ventilation, van volume, outside temperature and how warm you want the interior all matter.

For many insulated campervans, a genuine 2kW-class heater is a sensible place to start looking. Current 2kW systems from AUTOTERM and Webasto can modulate well below their maximum output, which makes them suited to maintaining heat rather than simply blasting a small space. Larger 4-5kW heaters make more sense where the van is genuinely large, poorly insulated, heavily glazed or expected to cope with more severe cold.

The important point is to size for heat loss, not for bragging rights. An oversized heater that spends most of its life turned right down is not automatically a better installation.

• 2kW-class heater: a sensible place to start for many small-to-medium, well-insulated campervans. It may take longer to warm a large cold interior, but its lower output can be easier to match to a compact living space.
• 4–5kW-class heater: more appropriate where the van is larger, poorly insulated, heavily glazed or used in more severe cold. The extra output can warm a high-loss interior faster, but may be more heater than a compact van needs.
• The deciding factor: actual heat loss, insulation and expected conditions matter more than van wheelbase or simply buying the largest heater available.

How a campervan diesel heater works

A diesel air heater has two separate air paths. Diesel is burned in a combustion chamber and the exhaust is routed outside. Separately, a fan moves cabin air across a heat exchanger and returns the warmed air to the living space. In a correctly installed system, combustion gases do not mix with the warm cabin air.

The heater still needs 12V power. The battery runs the controller, fan, metering pump and ignition system. That is why a diesel heater belongs in your electrical planning even though diesel provides the heat.

How much diesel does a campervan heater use?

Fuel use varies with model and output setting, so there is no honest single number for every diesel heater. A useful real example is the current AUTOTERM Air 2D: the manufacturer specifies roughly 0.10 to 0.24 litres per hour across its operating range. Webasto gives roughly 0.12 to 0.24 litres per hour for the 2kW Air Top 2000 STC.

Those figures show why diesel heating is attractive off-grid. They are examples from two current 2kW heaters rather than a promise that every heater will use the same amount.

How much battery power does a diesel heater use?

The 2kW rating is heat output. It does not mean a 2kW heater is drawing 2kW from your leisure battery. AUTOTERM specifies 10-29W while running for the Air 2D, and Webasto lists 14-29W for the Air Top 2000 STC. Start-up and shutdown also matter because the glow system and fan have work to do before and after normal combustion.

That means your leisure battery needs enough capacity and the wiring needs to deliver adequate voltage at the heater, particularly during start-up. If you are still planning the rest of the system, use our campervan electrical calculator to see how heating fits alongside your other daily loads.

Marketplace heater or manufacturer-backed heater?

This is not simply a question of “cheap bad, expensive good”. There are plenty of lower-priced diesel heaters sold through large marketplaces, and many self-builders use them successfully. The difficulty is that model names, specifications, manuals, controllers, supplied parts and seller support can vary from one listing to another.

With a manufacturer-backed heater such as an AUTOTERM Air 2D or Webasto Air Top 2000 STC, the attraction is not just the heater itself. You get a defined specification, installation documentation, a known control system and an established parts and support route.

I would compare any marketplace heater on those same points before buying: is the output clearly specified, is there a proper installation manual for that exact unit, what controller is supplied, what is included in the kit, what warranty is actually offered, and can you get replacement parts later? A vague “5kW” or “8kW” badge on its own tells you very little.

Two current 2kW Amazon options

Some of the product links in this article are Amazon affiliate links. If you buy through one of them I may earn a small commission, at no extra cost to you.

maXpeedingrods 2kW option: the maXpeedingrods 2kW diesel heater on Amazon UK is a compact 12V/24V heater sold for campervans, caravans and similar vehicles, with LCD, remote and Bluetooth app control. I have not installed or tested this exact kit, so I would check the supplied installation documentation and kit contents carefully before buying.

Another 2kW Amazon option: the OBAKL 2kW 12V diesel heater is another current option. The listing specifies a 2kW output, 12V operation, LCD controller and remote control, a 1-year limited warranty and suitability for RVs, trucks and boats. It also gives fuel consumption of 0.10–0.25 litres per hour. As with any marketplace heater, check the exact kit contents and installation instructions before buying.

Main diesel tank or a separate heater tank?

Both arrangements are common. On a diesel van, taking fuel from the vehicle tank avoids having another container to fill and can make day-to-day use simpler. On a petrol van, a diesel heater normally needs its own separate diesel tank because the vehicle tank contains the wrong fuel. A separate tank can also make sense on a diesel van where tapping the vehicle fuel system is impractical.

The choice affects installation, location and maintenance. I would make that decision before choosing the final mounting position rather than trying to squeeze a fuel system around a heater that has already been bolted down.

Where should a diesel heater be mounted?

Inside and underfloor installations are both possible on suitable heaters. The right position needs enough room for the heater itself, safe combustion-air and exhaust routing, sensible hot-air ducting, access for service and protection from water, road debris and stored belongings.

Do not choose the position just because it leaves the shortest hot-air duct. Before drilling anything, check what is above and below the floor and make sure the position works for the fuel, exhaust, intake, wiring and future servicing as well.

Can you fit a diesel heater yourself?

Yes, a diesel heater can be a DIY job for someone who is already comfortable working on a campervan’s 12V electrics, fuel system and bodywork, but it is not a good place to learn by trial and error. The heater has to be mounted securely and the electrical supply, fuel line, combustion-air intake, exhaust and hot-air ducting all need to be installed correctly.

The safest approach is to use the installation instructions for the exact heater you have bought rather than copying a generic diagram from another brand or model. Pay particular attention to the manufacturer’s requirements for mounting orientation, fuel-line routing, exhaust position, combustion-air intake, cable size, fusing and clearances from heat-sensitive materials.

If you are confident with those jobs and can check your work properly, DIY fitting is realistic. If you are unsure about the fuel connection, exhaust routing, cutting the floor, electrical supply or whether the chosen position is safe, I would use an experienced campervan or diesel-heater installer for those parts rather than guess.

A professional installation also makes sense if you want a main-tank fuel connection but are not comfortable modifying the vehicle’s fuel system, if access under the van is awkward, or if you simply want the installation checked before relying on it overnight in cold weather.

Whichever route you choose, fit and test a suitable carbon-monoxide alarm and let the heater complete its normal shutdown cycle rather than cutting the 12V supply while it is hot.

Diesel heater safety: the parts that matter

A diesel heater is a fuel-burning appliance, so installation quality matters more than whether the controller looks clever. The combustion-air intake and exhaust must remain separate from the cabin-air path, the exhaust must be routed safely outside, fuel components need to be secure, and hot parts need suitable clearance and protection.

This is the point where I would stop relying on generic internet diagrams. Use the installation instructions supplied for the heater, and if the fuel, exhaust or electrical side is outside your comfort zone, use an experienced installer. Fit a suitable carbon-monoxide alarm as an additional safeguard and test it regularly; an alarm does not make a poor installation acceptable.

Also let the heater complete its normal shutdown cycle. Cutting battery power while it is hot can prevent the controlled cool-down the unit is designed to perform.

Why diesel heaters soot up

Combustion problems can have several causes, including installation faults, poor fuel delivery, restricted air or exhaust flow, voltage problems and long periods of unsuitable operation. That is another reason not to treat every “diesel heater fault” as the same problem.

AUTOTERM’s own guidance recommends periodically running its air heaters at maximum power during periods of light use. Follow the maintenance and operating advice for your heater rather than assuming a rule from one brand applies unchanged to another.

What about altitude?

At altitude the air is thinner, so a heater needs the right fuel-to-air control to burn cleanly. Do not assume every controller automatically compensates. Some current systems include dedicated altitude control: for example, the current AUTOTERM Air 2D specification lists a high-altitude sensor and operation up to 4200m.

If mountain travel matters to you, make altitude capability part of the buying decision rather than assuming every electronic controller compensates automatically.

How noisy is a diesel heater?

There are several noises rather than one: combustion fan noise, warm-air movement and the repeated tick of the fuel pump. Mounting position, duct layout and how the pump is isolated from the vehicle structure can make a noticeable difference.

A bigger heater is not automatically quieter. The useful target is a heater that can comfortably meet the van’s heat loss without spending its whole life at either extreme of its operating range.

When an electric heater still makes more sense

If you nearly always stay on campsites with electric hook-up, a fixed diesel heater may be unnecessary complexity. A small mains heater can be cheaper, quieter and simpler when you already have paid-for EHU available. Our campervan electric heater guide covers that option.

For regular off-grid use, winter touring or nights where hook-up is not available, diesel heating becomes much more attractive because the heat comes from fuel rather than trying to turn a leisure battery into a space heater.

Do not forget the insulation

A heater only replaces heat the van is losing. Improving insulation and controlling draughts can reduce the heating demand before you spend money on a larger heater. If you are still at the build stage, read our campervan insulation guide alongside this one.

A sensible way to choose

Start with the van rather than the heater advert. Think about its size, insulation, glazing and the coldest conditions you genuinely expect to use it in. Then compare heaters that can cover that demand while still having a useful low-output range.

For many self-builders, that will put a genuine 2kW-class heater near the top of the shortlist. For larger or higher-loss builds, move up only when the extra output is justified. After that, decide how much you value documented specifications, warranty, diagnostics and long-term parts support.

That approach is less exciting than buying the biggest number on the listing, but it is much more likely to leave you with a heater that actually suits the campervan.