What size vehicle is the Air 4D best for?

Updated 09/03/2025 | Published 08/11/2025

Products Featured in This Question

Autoterm Air 4D Diesel Heater for RVs - 12v

(1)

$1169.36

Autoterm Air 2D Diesel Heater for Vans, Campers, Trucks, and Boats - 12v

$985.50

Question:

We’re building out a retired airport shuttle bus as a skoolie. Would the Air 4D be strong enough?

asked by: Jen

Expert Reply:

The Air 4D # AU96MR is a great choice for buses, medium RVs, or even marine cabins. It pushes up to 4kW of heat and moves 1,800 square feet of air per hour. That’s more than double what the Air 2D # AU56MR can do for not much more money.

It also comes pre-calibrated for altitudes up to 13,700’, which is a bonus if you’re heading into the mountains. What’s your insulation like? That’ll help keep this heat locked in the vehicle.

expert reply by: Andrew N

4D Contents
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Stan

9/3/2025

Good to know, Andrew. My shuttle has decent insulation but lots of windows. Do you think the 4D can keep up in winter, or should I plan on a backup heat source?

Andrew N.

9/3/2025

@Stan That’s a smart question, Stan. The Air 4D will absolutely hold its own in a well-insulated bus, but windows are always the weak spot - they can bleed heat fast in cold weather. Most folks pair the heater with insulated window coverings or curtains to cut that loss. With those in place, the 4D should keep you comfortable even in freezing temps. I've even had to use the plastic window rolls with tape and heat gun on an old house window, so I wonder if that would work for a temporary fix. That said, having a small backup like a portable electric heater (when shore power’s available) or even a catalytic propane heater gives peace of mind on really cold nights. Are you planning to spend most of your time in colder climates, or will this be more of a three-season rig?