Diesel heaters for motorhomes: are they worth it?
We fitted a diesel air heater to our motorhome after one too many cold mornings waiting for the slow system to catch up. Here is how they work, how they compare with gas and electric, and whether the upgrade is worth it, from a van we actually live in.
The short answer
For most people, yes. A diesel air heater runs off your van's own fuel tank, blows out warm air in minutes rather than the hour-plus a wet gas system takes, and costs far less to run than heating off your leisure batteries. We fitted one to our Dethleffs and it is now our primary heat from October onwards.
The one rule to remember: run it for half an hour every month, even in summer, or the fuel goes stagnant and the pump clogs. Do that and it will look after you for years.
Sometimes the best way to prove you have a problem is to spend a cold night with it. Our Dethleffs heats up eventually, but eventually is the issue. When Steve is using the van for work back home, he does not want to sit in his coat for an hour and a half waiting for the wet system to come up to temperature. We therefore booked in for a diesel heater, and the night before the install we got the proof we needed: three degrees overnight, electric heating run off the batteries, which were left at 23% by morning. That is the problem in a nutshell.
How a diesel heater works
Simpler than it sounds
A diesel air heater is a small unit, usually mounted up in the chassis, that draws a little fuel from your van's own diesel tank and burns it in a sealed chamber. The exhaust vents outside, and a fan blows the warm, dry air through ducting to vents inside the van. On ours there is a vent at each end, so the whole van warms evenly. Switch it on and within a few minutes you have warm air coming through. That speed is the entire point.
Because the burn is sealed and vents outside, the air coming into the living space is clean, and because it runs off the main fuel tank, there is no gas bottle to run out halfway through a cold night. If you have owned a van with a factory Webasto or similar, as we did in our old Swift Kon-Tiki, you already know the format. This is the same idea, retrofitted to a van that did not come with one.
Diesel versus gas and electric
Three ways to heat a van, honestly compared
Most motorhomes give you more than one source of heat. Here is how the three we run stack up, based on actually living with all of them.
Diesel air heater
It runs off the van's own fuel tank and blows warm air through the vents within minutes. It is cheap to run, there is no gas bottle to swap, and it warms the whole van quickly. This is now our primary heat from October onwards. The one job it does not do is heat your water, unless you fit a combined unit.
Gas or wet system
This is the factory setup in a lot of vans. It heats water and radiators, so it warms things evenly and does your hot water too, but it is slow. Our Dethleffs takes an hour and a half to come up to temperature on the wet system, which is no good when you want warmth straight away. We keep it as backup.
Electric off the battery
This is fine when you are plugged in on a campsite, but it is a poor idea off grid. On a cold solo night we ran electric heating off the leisure batteries and had them down to 23% by morning. It will keep you warm, but it is not the right tool for the job, and it drains your power quickly.
We have not thrown anything out. The gas and electric systems stay in as backup, and the air conditioning can push warmth too, so we go into winter with three sources of heat, but the diesel heater is the one we reach for first.
Our Autoterm, honestly
What the install and the first weeks were like
We had ours fitted by Autoterm, just over the border in North Wales. The unit went up into the chassis in a neat box; they tapped into the diesel tank through an existing access point with no drilling, which matters for warranty, and ran the ducting to a vent at each end of the van. Within a few minutes of switching it on we had warm air, not the hour and a half we were used to. It really is a matter of minutes.
Run it for thirty minutes every month, even when you do not need the heat. Diesel can go stagnant in the pipe, and if it sits all summer you get diesel bug building up that clogs the pump the moment you fire it up in September. Our unit tells us when thirty days is up, which is handy, because we would absolutely forget otherwise.
A few weeks in, it has done exactly what we hoped. There is also a clever combined unit coming that uses a diesel heater to do your hot water and warm air from one box, which is worth knowing about if you are building a van from scratch. For us, retrofitting the air heater alone was the right call.
Is it worth it?
For the way we use the van, it is easily worth it. It gives us fast heat, cheap running, no gas bottle to babysit, and the peace of mind of not draining the batteries to stay warm off grid. If you wild camp into autumn and winter, or you use your van for work in the cold like Steve does, it is one of the best upgrades you can make.
One practical note: do not leave it until the first cold snap, because that is when everyone else books in and the diaries fill up. If you are thinking about it, get your quote in while it is quiet. Autoterm are a genuine sponsor of ours, and our code RR10 gets you 10% off the heater and the install at autoterm.store. We would only ever put our name to kit we actually run, and this is on our own van.
Diesel heater questions we get asked
What is a diesel heater?
A diesel air heater is a compact unit that draws a small amount of fuel from your van's own diesel tank, burns it in a sealed chamber, and blows the resulting warm air through ducting to vents inside. The exhaust vents outside, so the air coming into the van is clean and dry. Ours warms the whole van within a few minutes of switching on.
Are diesel heaters expensive to run?
No, they are one of the cheapest ways to heat a van. They sip diesel from the main tank rather than burning through gas bottles or draining your leisure batteries. Compared with running electric heating off the battery, which we did one cold night and dropped to 23%, a diesel heater is far more efficient and far less stressful off grid.
Diesel heater versus gas, which is better?
For fast, cheap heat, diesel wins. A wet gas system heats evenly and does your hot water, but it is slow, our van takes about an hour and a half to warm through on it. A diesel air heater gives you warm air in minutes off your existing fuel, with no bottle to swap. We keep the gas system as backup and run the diesel heater as our primary.
Can you fit a diesel heater to any motorhome?
In most cases, yes. Ours was retrofitted to a van that came with a slow wet system. The installer tapped into the diesel tank through an existing access point with no drilling, which matters for warranty, mounted the unit up in the chassis, and ran ducting to a vent at each end of the van. A good installer makes it a tidy job.
Do diesel heaters smell or are they unsafe?
The combustion is sealed and the exhaust vents outside, so the warm air coming into the living space is clean, with no fumes. You may get a brief smell on start-up as it fires, which clears quickly. As with any heater, have it fitted properly and keep a carbon monoxide alarm in the van as a sensible precaution.
How often should you run a diesel heater?
Run it for around thirty minutes every month, even in summer when you do not need the heat. Diesel can go stagnant in the pipe over a long idle spell, and diesel bug will clog the pump the moment you try to fire it up in autumn. Some units even remind you when thirty days is up, which is genuinely useful.
Written by Steve and Lyndsay Radford. The heater described here is the Autoterm unit fitted to our own Dethleffs XL Family, and Autoterm is a sponsor of ours. Everything else comes from living with it, not from a brochure. Roaming Radfords is a trading name of Yowzer Limited.