Petrol vs Diesel vs the Coming Electric Motorhome: A Realistic Running Cost Breakdown

When you are staring at a motorhome forecourt, it is easy to get swept up in the layout, the upholstery, and the size of the fridge. But beneath that shiny fibreglass body sits a heavy commercial chassis, and moving three and a half tonnes of it around the country is not cheap. For decades, the UK motorhome market has been entirely dominated by diesel. Now, with petrol vans making a quiet resurgence and fully electric commercial chassis like the Fiat e-Ducato arriving on the scene, the question of what powers your motorhome has never been more relevant.

As someone who spends a lot of time looking at data rather than brochures, I want to strip away the marketing claims and look at the real world running costs. We are going to examine genuine MPG figures, current fuel prices, and the stark reality of where electric motorhomes currently stand.

The Reigning Champion: The Diesel Coachbuilt

Let us start with the benchmark. The vast majority of coachbuilt motorhomes in the UK are built on a diesel Fiat Ducato, Peugeot Boxer, or Ford Transit chassis. The appeal of diesel has always been torque, the low down pulling power required to haul heavy loads and fuel efficiency. But what does that efficiency look like in the real world?

If you ask a dealer, they might suggest a modern Euro 6 diesel motorhome will achieve well over 30 MPG. The reality, drawn from thousands of owners tracking their fill ups, is slightly less optimistic. A typical 3,500 kg coachbuilt motorhome driven sensibly on a mixture of A roads and motorways will return between 26 and 30 MPG. A heavier tag axle or A-class model might drop into the low twenties, while a particularly aerodynamic low profile driven at 55 mph might occasionally touch 32 MPG.

Using an average of 28 MPG, a diesel motorhome travels roughly 6.1 miles per litre. At the current average UK diesel price of around £1.75 per litre, your fuel cost is approximately 28.4 pence per mile. That means a 1,000 mile touring holiday to the Scottish Highlands and back will cost you just over £280 in fuel. It is a known, predictable quantity, supported by a fuel network that exists on every corner.

The Petrol Alternative: Smooth but Thirsty

Petrol coachbuilt motorhomes are incredibly rare in the UK, but they are beginning to appear as smaller campervans adopt petrol engines to avoid diesel emission zone charges. If manufacturers were to start building full size coachbuilt motorhomes on petrol chassis such as the Ford Transit with an EcoBoost engine, how would the numbers stack up?

Petrol engines are inherently less efficient than diesels when moving heavy, un-aerodynamic loads. A petrol engine lacks the low down torque of a diesel, meaning it has to rev harder to maintain speed, particularly on inclines. Based on commercial van data, a petrol coachbuilt motorhome would likely return around 18 to 22 MPG in the real world.

Taking an average of 20 MPG, that equates to 4.4 miles per litre. Even though petrol is currently cheaper at the pumps, averaging £1.58 per litre, the poorer fuel economy means your running cost jumps to 35.9 pence per mile. That same 1,000 mile Scottish tour would now cost you £359. You gain a quieter, smoother engine and avoid DPF issues, but you pay a 25 percent premium on every mile you drive.

The Electric Horizon: The Reality of the e-Ducato

This brings us to the electric motorhome. We are already seeing electric campervans based on the VW ID Buzz and Fiat e-Scudo, but a full size coachbuilt motorhome requires a heavy duty chassis like the Fiat e-Ducato. The e-Ducato is available with a large 110 kWh battery, which sounds impressive until you bolt a motorhome body to it.

Weight and aerodynamics are the enemies of electric range. A bare e-Ducato panel van might claim over 200 miles of range, but once converted into a fully laden 3,500 kg motorhome with the aerodynamic profile of a brick, real world testing suggests that range plummets. Owners and early testers report that a heavy electric conversion will realistically cover between 80 and 110 miles on a full charge.

The running costs, however, are where electric vehicles become complicated. If you charge that 110 kWh battery at home on a standard domestic tariff (currently capped at roughly 26 pence per kWh), it costs about £28 for a full charge, giving you a running cost of around 28 pence per mile, almost identical to diesel. If you charge overnight on a cheap EV tariff at 8 pence per kWh, that drops to an incredible 8.8 pence per mile.

The Public Charging Trap

The problem is that you cannot tour the country charging overnight on your driveway. When you are on the road, you are entirely reliant on the public charging network. Public rapid chargers currently average around 70 pence per kWh. At that price, a full charge costs £77. If that only gets you 100 miles down the road, your running cost suddenly skyrockets to 77 pence per mile. That 1,000 mile Scottish tour would cost an eye watering £770 in electricity alone.

Furthermore, public charging infrastructure is simply not designed for motorhomes. Most charging bays are tight, short spaces designed for hatchbacks. Trying to manoeuvre a 7.5 metre coachbuilt motorhome into a standard charging bay without blocking the road or taking up three spaces is practically impossible.

Where Electric is (and is not) Viable

So, where does this leave us? If you are looking at a small pop-top campervan that doubles as a daily driver, electric makes sense. You can charge it cheaply at home, the range is respectable, and it fits into standard charging bays.

But for a full size coachbuilt motorhome, the technology is simply not there yet. The batteries are too heavy, eating into your payload. The range of 100 miles means you would have to stop and charge every two hours, and when you do stop, the chargers are too expensive and the bays are too small. For now, despite the changing landscape of motoring, the traditional diesel engine remains the only truly viable option for the touring motorhome owner.