Diesel Heater

Two things follow from that description, and between them they decide most of what matters when choosing one.

The first is that a diesel heater is a combustion appliance living inside a small sealed box that people sleep in. Its exhaust gases stay outside the van only for as long as the exhaust path stays sealed and the air intake stays clear of them. So the fitting question is not where the unit goes, but where its intake, its exhaust and its fuel line run — and a carbon monoxide alarm belongs in any van carrying one. The clearances that govern this are set per model by the manufacturer's installation manual, and this page does not restate them: getting them approximately right is the failure mode, not a starting point.

The second is that it burns the fuel already in the tank. That removes the refill and storage question which governs gas heating, and replaces it with a dependency — the heater and the engine draw on the same tank, so heating through a cold night eats into range.

Two comparisons often repeated about diesel heaters are deliberately not made here. Fuel consumption and noise relative to LPG units vary by model and by installation, and no source cited on this page publishes a comparison spanning both categories; wherever you meet a figure, ask which two specific units it compares. Nor does this page rank manufacturers. The reliability differences widely reported between established brands and low-cost units are not documented by any source we cite, and repeating them without one would be an opinion wearing the clothes of a specification.