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It's the most common heating question we get at RV Supplies, and it's a good one. Walk into a showroom or start googling 'best heater for my caravan' and you'll quickly find yourself lost in a tangle of specs, fuel types, and product names. Air heater. Water heater. Combi. Diesel. Gas. 12V. 2kW. 4kW.

So let me break it down in plain language, because the right heating setup makes winter travel genuinely comfortable, and the wrong one makes it miserable.

What's the Difference Between an Air Heater and a Water Heater?

It's simpler than it sounds.

An air heater burns diesel fuel (or uses electricity) to heat air, then blows that warm air into your living space through ducts or a vent. Think of it like a compact, efficient furnace designed specifically for the confined space of a van or motorhome. It heats the space fast, uses very little fuel, and runs off your 12V battery system, which means it works perfectly off-grid.

A water heater, on the other hand, heats the water in your system: for your shower, your taps, and sometimes a hot water radiator circuit as well. It doesn't heat the air directly.

A combi system does both. One unit, two functions. This is what the Truma Combi 4E does, and why it's so popular in premium motorhome and caravan builds.

Do I Need Both?

Honestly? It depends on how you travel.

If you're doing short winter trips and mostly stopping at powered sites, a water heater alone might be enough. You'll have your shower sorted and you can use the site's electrical connection to run a small fan heater for warmth.

But if you're freedom camping in the South Island, heading to Wanaka, Queenstown, or Fiordland during winter, or if you're spending weeks at a time on the road, you want air heating. You want something that fires up at midnight when it's 2 degrees outside and has the van warm before you have to get up. That's what a quality diesel air heater does.

The Products I Recommend in 2026

For Air Heating: Autoterm Air 2D (12V Diesel)

This is my go-to recommendation for customers who want reliable, efficient diesel air heating. The Autoterm Air 2D runs off 12V, so it works perfectly with your battery and solar setup. It draws very little power (around 10 to 15W once running) and produces 2kW of heat, which is more than enough for a standard caravan or small motorhome.

I've seen a lot of cheap diesel heaters come through workshops. The Autoterm is not in that category. It's made in Latvia by a company that builds heating systems for heavy-duty commercial vehicles and military applications. They build them to work in minus 40 degrees. A cold night in the Mackenzie Basin is well within its comfort zone.

For Combined Air and Water: Truma Combi 4E Plus

If you want one elegant solution that handles both air and water heating, the Truma Combi 4E is what I'd install in my own van. It runs on LPG for freedom camping and switches to electric boost on powered sites. It's quieter than most diesel air heaters, the hot water recovery is fast, and Truma's build quality is exceptional.

Truma has been making RV heating systems for over 70 years. They supply the European motorhome industry at the top end. When you buy a Truma, you're buying engineering that's been tested and refined over decades of real-world use in genuinely harsh conditions.

Coming Soon: Autoterm Baltica System

We're very excited about this one. The Autoterm Baltica is a brand new all-in-one integrated system that combines air and water heating in a single, compact package. It's specifically designed for demanding environments: RVs, caravans, and marine applications. It represents the next generation of Autoterm engineering. 

What About the Cheap Options Online?

I get it. You've seen cheap as chips diesel air heaters on TradeMe or Chinese marketplaces. And yes, some of them work. For a while.

Here's what I've seen in the workshop:

• Inconsistent starting, especially in cold weather
• Electrical connectors that corrode or fail
• Fuel pumps that wear out quickly
• No local warranty support: you're on your own when it breaks
• No access to spare parts in New Zealand

A cheap heater that fails after one winter isn't a bargain. A quality Autoterm or Truma that lasts 10 or more years with minimal maintenance is the better investment. And when something does need attention, we're here to help.

Ready to Choose?

Come and see us at the Christchurch Motorhome Show in May. Rob will be there to answer your questions in person. Or browse our full heating range online at rvsupplies.co.nz, or call the team and ask to speak with our heating specialist.

Stay warm out there.

Rob Ferguson, Heating Specialist, RV Supplies