Campervan Diesel Heaters: The Complete Guide

Overview

Heating is the difference between a campervan you use twelve months a year and one that hibernates from October to March. For most UK owners, a diesel heater is the answer: it runs off the same fuel as the vehicle, sips power from the leisure battery, and produces dry, ducted warm air that keeps the living space comfortable even when it is frosty outside.

This guide explains how diesel heaters work, how to size one, what they genuinely cost to run, and how to approach installation and safety — including where a professional converter earns their fee.

How a Diesel Heater Works

A diesel air heater is a small combustion unit, usually mounted under a seat or bed, that draws fuel from the vehicle's own diesel tank (or a separate fuel tank) via a small 12V fuel pump. Inside, fuel burns in a sealed combustion chamber. A fan blows air from inside the camper across a heat exchanger and pushes warm air out through ducting to vents in the living space.

The critical design point is that the two air paths never mix. Combustion air is drawn from outside through a dedicated air intake, and the exhaust gases are expelled outside through the exhaust pipe. The air you breathe only ever touches the outside of the heat exchanger. Done properly, this makes a diesel heater one of the safest ways to heat a camper van.

Control is via a control panel or controller — a simple dial, or a digital thermostat with timers and on some models a phone app. Set a temperature and the heater modulates its heat output to hold it.

What Size Diesel Heater Does Your Van Need?

These units are rated by output in kilowatts (kW), and bigger is not better. An oversized heater cycles constantly and soots up rather than settling at its efficient cruising output.

2kW — the right choice for the vast majority of UK campervans. A VW Transporter, Vivaro or Trafic-sized camper, or even a medium-wheelbase Transit, holds temperature comfortably on a 2kW unit running at partial output.

4kW–5kW — for large high-roof vans such as long-wheelbase Sprinters and Ducatos, poorly insulated builds, or anyone planning genuine winter van life in exposed spots. Even then, a 5kW unit will spend most of its time turned well down.

8kW — marketed on budget units, rarely an honest figure, and almost never necessary in a campervan. Treat these claims sceptically.

The better your insulation, the smaller the heater you need and the less it costs to run — read our insulation guide alongside this one, because the two decisions are linked.

Running Costs: The Honest Numbers

Running costs are genuinely low. On a low-to-medium setting, a 2kW unit burns very roughly 0.1 to 0.2 litres of fuel per hour. In practice, most owners find that heating a well-insulated van through a cold evening and overnight uses somewhere around one to two litres of diesel fuel. At typical UK pump prices, that is a couple of pounds a night, often less.

Power consumption from the 12V electrics is modest too. There is a spike at startup while the glow pin ignites the fuel, then the fan and fuel pump draw a small steady current — a healthy leisure battery handles a full night's running with capacity to spare. That is why they dominate off-grid builds.

Installing a Diesel Heater: DIY or Professional?

Fitting a diesel heater is a legitimate DIY job for a competent builder working on their own van conversion. A typical heater kit includes the unit, mounting plate and bracket, fuel pump, fuel line, exhaust, air intake, ducting, vents and wiring loom. Diesel heater installation means cutting holes in the van floor for the exhaust, intake and fuel line, tapping into a fuel supply, and wiring into the 12V system. Follow the installation guide step-by-step and take particular care with the fuel pump angle and exhaust routing.

That said, there is a strong case for professional installation:

A professionally fitted unit from an established brand typically costs somewhere in the region of £1,500–£2,500 supplied and installed, depending on the model and the complexity of the van build. If you are commissioning a full conversion, this is exactly the kind of job worth leaving to the professionals — any good converter in our directory fits heating as standard and stands behind the work.

Safety: The Non-Negotiables

These heaters have an excellent safety record when installed correctly. The risks come from poor installation, not the technology.

Alternatives: LPG and Electric Heating

LPG (gas) heating — blown-air gas heaters and combi units (the Truma Combi being the best known) heat the space and, in the combi's case, your hot water too. They are quiet and effective, but you are carrying gas bottles, refills need planning, and the installation must be certified. A combi is a strong choice for a motorhome or larger build where hot water matters.

Electric heating — a small 230V fan heater or oil-filled radiator is cheap and works well on a campsite with hook-up, but it is not an off-grid solution: the power draw would flatten even a large lithium bank within hours through an inverter. Treat 240V electric heat as a hook-up bonus, not a heating system.

For most UK campervans the practical answer is a diesel air heater for space heating, with gas or electric covering cooking and hot water.

Maintenance: Keeping It Healthy

These are simple machines and mostly look after themselves, but three habits keep them reliable:

One quirk: combustion needs the right fuel-to-air mix, so at high altitude the unit can smoke or shut down. Several premium brands offer altitude adjustment — worth checking if you plan Alpine trips.

Budget Units vs Premium Brands

The elephant in the room: a Chinese diesel heater can cost a tenth of the price of a German-made unit from Webasto or Eberspacher, with Autoterm (formerly sold as Planar) sitting between the two and earning a solid reputation among UK vanlifers. So is the best diesel heater simply the cheapest one that works?

Honestly: many people run budget units for years without trouble, and many converters will not touch them. Premium brands buy you consistent build quality, documentation, parts support and a dealer network; budget units buy you a very low price and a lottery on quality control. If it is going into a build you will rely on in January, the middle ground — a mid-priced 12V diesel heater from a brand with UK parts support, professionally installed — is where the value peaks.

Frequently Asked Questions

Are diesel heaters safe in campervans?

Yes — when installed correctly. The combustion chamber is sealed and exhaust gases vent outside, so the air in the van never mixes with fumes. The essentials are a properly routed and sealed exhaust, the correct air intake, and a working carbon monoxide alarm as a backstop.

Can you leave a diesel heater on all night?

Yes — running overnight is normal use, and steadier than repeatedly cycling it on and off. Set the thermostat low, check the CO alarm works, and leave a vent cracked for fresh air. The heater will sip fuel and battery slowly through the night.

How much diesel does a campervan heater use?

Roughly 0.1–0.2 litres per hour at low-to-medium output for a 2kW unit. A cold evening plus a full night's heating typically uses one to two litres — a couple of pounds at UK pump prices.

How much battery does a diesel heater need?

Surprisingly little. Startup draws the most while the glow pin heats, then consumption drops to a small steady draw for the fan and pump. Any healthy leisure battery will run one overnight; it is one of the most battery-friendly ways to heat a camper.