How to Heat a Campervan in Winter: A Complete UK Guide

If you want to keep using your van after the clocks go back, whether that means frosty surf mornings in Cornwall or a ski trip to the Alps, heating is the first thing to get right. Here at Van Junkies in Gosport, Hampshire, we design and build off-grid power systems for vans that get used all year round, and winter is where a poorly planned setup gets found out fast. This guide covers how to heat a campervan in winter without flattening your leisure battery. A winter campervan heating setup is the combination of insulation, a fuel-burning space heater, and enough battery charging to keep a van warm and powered through cold, dark months without mains hook-up. If you would rather skip the maths, our Kit Recommender will point you towards the right power setup for your van.

To heat a campervan in a UK winter, insulate first, then fit a diesel air heater, which for most vans means a 2kW unit rather than a bigger one. Because winter solar output drops sharply, back it up with a lithium leisure battery and a DC-DC charger so your alternator tops up the battery every time you drive.

The essentials at a glance:

• Winter Solar: In a UK winter, van solar panels often produce only around 10 to 30 percent of what they manage in midsummer, because the days are shorter and the sun sits much lower in the sky.
• Heater Fuel Use: A 2kW diesel air heater typically uses around 0.1 to 0.25 litres of diesel per hour, depending on the heat setting.
• Heater Power Draw: A diesel heater draws roughly 8A to 12A from your leisure battery for a few minutes while the glow plug starts it, then drops to around 10W to 30W once it is running.
• Alternator Charging: A 50A DC-DC charger such as the Victron Orion XS can put up to 50Ah into your leisure battery for every hour of driving, as long as your alternator can supply the current.
• Altitude: Many standard diesel heaters are set up for use near sea level and can run rich and soot up above roughly 1,500 metres unless they have altitude compensation or a high-altitude setting.
• Cold Batteries: Most lithium (LiFePO4) leisure batteries must not be charged below 0°C, so in winter they should sit inside the heated living space or have built-in low-temperature charge protection.

1️⃣ Insulate First, Then Heat

Bare sheet metal loses heat fast. Every uncovered steel panel in your van pulls warmth out of the air inside and hands it to the cold outside, so a heater in an uninsulated van is fighting a losing battle. Get the insulation right first and a small heater will keep you warm on very little fuel and power.

Most good van builds use two layers of insulation, plus a way to get rid of damp air:

• Closed Cell Foam Liner: A thin foam layer with a foil face, stuck straight to the bare metal. It stops the cold steel chilling the air inside, and because it does not soak up water it helps keep condensation off the metal, which is where rust starts.
• Synthetic Fibre Insulation: A thicker layer in the deeper cavities, such as 3M Thinsulate. It traps air to slow heat loss, and unlike household glass fibre or natural wool it does not hold on to moisture.
• Ventilation: You breathe out, cook, and dry wet kit inside the van, and all that moisture has to go somewhere. A roof vent cracked open, even in winter, lets damp air out and makes the space easier to heat.

Pro Tip: Cover as much bare metal as you can with the foam layer, including the backs of ribs and pillars. Any steel left exposed becomes a cold spot where condensation collects overnight.

2️⃣ What Size Diesel Heater Does a Campervan Need?

For most campervans, the answer is a diesel air heater. It draws fuel from your van's own tank, uses a small amount of 12V power to run its fan, fuel pump, and glow plug, and blows warm, dry air into the living space. There are no gas bottles to swap, and it keeps running for as long as you have diesel. Every diesel heater we supply is CE certified, with options starting at around £500. When something is burning fuel inside your living space, that certification matters.

Bigger is not better. For a well insulated van like a VW Transporter, Ford Transit Custom, or Mercedes Sprinter, a 2kW diesel heater is the right size. On a medium setting it gives steady warmth and uses around 0.1 to 0.25 litres of diesel an hour.

A 5kW heater in the same van is a common mistake. It heats the space so quickly that the thermostat keeps it on its lowest setting most of the time. At that low output the burner never gets hot enough to burn the fuel cleanly, so carbon soot builds up on the burner and glow plug until the heater starts to smoke, struggles to light, or stops altogether. Save the 5kW units for big motorhomes, box bodies, or large spaces that are hard to insulate.

• Exhaust Safety: A diesel heater burns fuel, so it produces carbon monoxide. The exhaust must be routed safely outside the vehicle and the heater installed to the manufacturer's instructions. If you are not confident, have it fitted or checked by someone qualified.
• Carbon Monoxide Alarm: Fit a CO alarm in the living space whatever heater you choose. It costs very little and it could save your life.
• Fusing: Fuse the heater's power supply to the rating given in its manual, allowing for the higher current it draws while the glow plug starts it.

Pro Tip: Every so often, run your heater on full power for 15 to 20 minutes before switching it off. The extra heat helps burn off carbon deposits in the burner and keeps it lighting reliably all winter.

3️⃣ Heading to the Alps? Diesel Heaters at Altitude

Most diesel heaters are set up for use near sea level. As you climb, the air gets thinner, so less oxygen reaches the combustion chamber. A standard heater keeps pumping in the same amount of fuel, the mixture runs rich, and you get black smoke, soot build-up, and eventually a heater that will not light.

That is not a problem anywhere in the UK, but it matters if you take your van skiing or over the high passes in Europe. Many standard diesel heaters start to struggle above roughly 1,500 metres. Some models have automatic altitude compensation, which senses the thinner air and adjusts the fuel and fan to suit, while others offer a high-altitude setting or kit. If mountain trips are on your list, check this before you buy.

4️⃣ Will Solar Keep Up in a UK Winter?

Not on its own. In midsummer the UK gets around 16 to 17 hours of daylight. Around the winter solstice that drops to roughly 7 to 8 hours in the south of England, and less the further north you go. The sun also sits low in the sky, so its light passes through more atmosphere and hits a flat roof panel at a shallow angle.

Put together, your panels often produce only around 10 to 30 percent of their midsummer output in a UK winter, and a run of grey days can push it lower still. A 400W array that keeps you going easily in July might only cover your fridge and lights on a good December day. Cold panels are actually slightly more efficient than hot ones, but that small gain does not make up for the lack of light.

Your battery choice matters here. Lithium (LiFePO4) leisure batteries, such as those from Fogstar and Beyond Batteries, accept a fast charge almost all the way to full, so they make the most of short bursts of sun and short drives.

Pro Tip: Most lithium leisure batteries must not be charged below 0°C. Keep your battery inside the heated living space rather than under the van or in an unheated locker, and check it has low-temperature charge protection before you head out in a cold snap.

5️⃣ Charging From Your Alternator in Winter

With solar output down, your engine's alternator becomes your main source of charge in winter. A DC-DC charger sits between your starter battery and your leisure battery. It works with modern smart alternators, protects your starter battery, and gives your lithium battery the correct multi-stage charge every time you drive.

Charger size makes a big difference on short winter drives. A 30A charger puts up to 30Ah into your battery per hour of driving, while a 50A unit puts in up to 50Ah, as long as your alternator can supply the current. Older DC-DC chargers can run hot at full output and cut back their charge rate to protect themselves. The Victron Energy Orion XS 50A is rated at up to 98.5 percent efficiency, so it wastes very little energy as heat and is built to hold its full output.

Pro Tip: If your winter trips involve lots of parking up and not much driving, a bigger lithium battery gives you a larger buffer between drives. Our full power system kits are designed around this balance of battery, solar, and alternator charging.

6️⃣ Free Bespoke Winter Van Electrical Design

Every van is different. Your heater, battery, solar, and alternator charging all need to work together, and the right balance depends on how you use the van, how much roof space you have, and how far you drive between stops. If your build does not fit a standard kit, our team offers a free bespoke campervan electrical and solar design service. We will look at your power needs and winter plans, then design a system that keeps you warm and powered through the colder months.

Planning to use your van right through the winter? Call our UK team on 023 935 52732 or WhatsApp us via the website chat and we will help you find the right heating and power setup for your build.