Cold weather camping in a Mars caravan is genuinely pleasant — with the right setup. Get it wrong and you're dealing with condensation, frozen pipes, dead batteries and a miserable trip. Here's how to do it properly.

The Three Cold-Weather Problems

1. Staying warm enough to sleep
2. Keeping condensation under control
3. Stopping water lines from freezing

Heating — Your Options Ranked

Diesel Heater (Best for Off-Grid Cold)

Mars vans fitted with a diesel heater (AU Focus or similar) have the right tool for the job. Diesel heaters:

• Use diesel for heat (cheap, available everywhere, and you're already carrying it in the tow vehicle)
• Only need a small amount of 12V to run the fan and controls — minimal battery impact
• Heat rapidly and hold temperature reliably
• Run silently outside, gentle hum inside

The right answer for sub-zero off-grid nights. Run continuously through the cold hours on low-medium setting rather than blasting it.

Reverse-Cycle Aircon (Heating Mode) — On Mains

If your aircon is reverse-cycle and you're on mains power, you can use it for heat. Works fine in mild cold (5–15°C). Becomes inefficient and slow below about 5°C. Not the right choice off-grid — pulls a lot of power.

Truma Combi Systems

Some Mars vans have Truma Combi units that do gas/diesel heat and hot water in one. These are efficient and well-engineered — follow the unit's manual for your specific model.

What Not to Use

• Portable gas heater (unflued): dangerous in a small space. Produces moisture and CO. Never run an unflued gas heater inside a caravan for sleeping.
• Camping stove for warmth: same issue, plus fire risk.
• Electric blankets on inverter: works on mains, but burns through batteries fast off-grid.

Sleeping Warm

• Set the heater to around 15–17°C overnight — much warmer than that and you'll wake up dehydrated.
• Layer bedding rather than relying on one heavy doona.
• Beanies and bed socks make a surprising difference.
• Position the bed away from cold walls if you can.
• Crack a roof vent slightly — air exchange beats sealed-and-condensating.

Condensation — The Bigger Enemy

Condensation is the biggest cold-weather problem in any caravan, especially pop-tops and hybrids. Two adults sleeping in an enclosed van produce 1–2L of moisture overnight from breathing alone. That moisture has to go somewhere. In a cold van, it condenses on the coldest surfaces — windows, walls, canvas, around vents.

Persistent condensation leads to mould, fabric damage and a damp, miserable van.

Reducing Moisture Production

• Cook outside where practical. Boiling pasta inside dumps a lot of water vapour.
• Lid on every saucepan when you do cook inside.
• Hang wet towels and clothes outside, not inside.
• Don't run the kettle excessively inside.

Removing Moisture

• Crack roof vents and windows even in cold weather. A small amount of air exchange dries the air without losing much heat.
• Run a 12V dehumidifier (small ones exist) or absorbing pucks.
• If you have dehumidifying mode on the aircon (on mains), it works well in cool damp conditions.
• Wipe windows and any visible condensation every morning before it has all day to soak in.

Hybrid & Pop-Top Specific

Canvas roofs and walls absorb and release moisture differently to hard sides. They're naturally more breathable, which helps, but they also wet through in heavy condensation. Get the van fully dry before packing down — never pack damp canvas. See Canvas & Annexe Pack-Down in the existing help centre.

For a deeper dive specifically on this issue, the existing help centre article Condensation in Hybrid and Pop-Top Caravans covers it well.

Frozen Water Lines

This catches people out who haven't camped in real cold before.

Water Lines Outside or Underneath

The most vulnerable lines are external — hot water inlet, hot water outlet to external shower, any exposed pipework. These can freeze at any sustained sub-zero overnight.

Pump and Tank

Internal pumps and tanks generally stay warmer than ambient (especially with the heater running inside) but exposed lines underneath the van are at risk.

Prevention

• Drain external lines before sub-zero overnight. Disconnect any hose to the external shower, drain hot water hoses you're not using.
• Drain the hot water system if you're not using it overnight in extreme cold. Easier to refill in the morning than to thaw or replace a cracked tank.
• Run the heater inside to keep the van and the water lines warmer than ambient.
• Insulate exposed pipework with foam pipe insulation if you regularly camp in cold areas — cheap from any hardware store.

If Lines Are Frozen

• Wait for daytime warming — usually thaws naturally.
• Don't run the pump hard against frozen lines — you'll burn the pump out.
• Don't apply direct heat (heat guns, hair dryers) — risk of cracking thawing pipes.
• Once thawed, check for leaks at fittings. Cold cycling can loosen connections.

Battery in the Cold

Lithium batteries discharge fine in the cold but won't charge below 0°C — see the full picture in Lithium Charging Below 0°C.

Practical implication for cold camping: plan for limited recharge on cold mornings. Solar might not start contributing until the battery has warmed naturally — often well past dawn.

Gas in the Cold

• Propane (the gas in your bottles) works down to about -42°C — well below anything you'll camp in.
• However, vaporisation slows in extreme cold, so very high-demand appliances may run noticeably slower.
• Bottles in shade and on the cold side of the van vaporise more slowly than bottles in the morning sun.
• If you're heading high country and using gas heat, two bottles open in changeover often performs better than one bottle on the hard work.

Awning & Setup in Cold

• Roll awnings up at night — frost and overnight wind aren't friends of unrolled awnings.
• Annexe walls help wind protection but trap moisture — keep an air gap somewhere.
• Pegs go in harder in frozen ground. Drive in before it freezes overnight, not after.

Driving Out in Cold

• Black ice on shadowed sections of road first thing in the morning is the biggest risk.
• Caravan brakes work less effectively cold — give them more distance to start being responsive.
• Allow longer warm-up time on the tow vehicle before pulling out.

What to Pack for Cold Trips

• Quality sleeping setup — proper doonas, warm sheets, beanies, socks
• Foam pipe insulation (and ties)
• Extra diesel for the heater (or full tank in the tow vehicle and good siphon kit)
• Absorbing pucks or small dehumidifier for condensation
• Backup heating plan if the diesel heater fails — electric on mains, heated mattress pad, whatever fits your van
• Warm clothing for outside — early starts in 0°C are brutal without it

The Reward

Cold-weather camping is genuinely brilliant once you have the setup sorted. Empty campsites, clear winter skies, no flies, no other vans within sight. Worth doing properly.

Related: Lithium Charging Below 0°C· Condensation in Hybrid and Pop-Top Caravans · Hot Weather Camping