The small diesels like VW Polo etc have resistive heaters as otherwise it would take too long for comfort to heat up the cabin.

Also don't forget that seat heaters are also resistive and most cars in cold climates have them.

> Also don't forget that seat heaters are also resistive and most cars in cold climates have them.

I know it (or more like my bum) too damn well, though I didn't think about them in this case.

> small diesels like VW Polo

Makes sense, though as I understood, it's strictly auxiliary till the engine is heated aaaand maybe some additional heating at the parking lot with the engine turned off, though I would wary of this usage, it would drain even the extended battery fast.

Overall it's not quite what I had in my mind (think of space heaters), though yes, there are some parts which can operate independently from the engine, though it's not a primary function for them.

Thanks for the hint.

There's also these https://www.disco3.co.uk/wiki/Fuel_Burning_Heater that can be run with the vehicle engine off.