I've converted a RAM Promaster City van into the moral equivalent of a "self-propelled teardrop trailer". In other words, it is tiny inside. The total interior space amounts to about 170 cubic feet (4'x5'x8.5').

I am interested in adding a small heater. I've insulated the vehicle very well, and with so little cubic footage -- and considering the body-heat output of two sleepers -- the BTU requirement should be very minimal.

At the same time, a heater would have to be zero-emission in such a small space. So I am looking for something that uses electric power. (Which is OK - the rig is wired for shore power, and in cold weather I won't be camping in places where there is no shore power available.)

Moreover, the bed platform sits about 16" above the van floor, and covers nearly all the available square footage (apart from the driver/passenger cabin), meaning the heater would have to sit beneath it.  Thus, a tiny form-factor and fail-safe against overheating are both requirements.

Does anyone know of a product that would fit the bill?

https://www.propexheatsource.com/vw-bus-vanagon-eurovan-heaters/&ved=2ahUKEwifktPhw8fmAhVYVc0KHUOoDrIQFjAAegQIAhAC&usg=AOvVaw3fE-0WOXdiCPcyBXs57Oz f" rel="external nofollow noopener" target="_blank">Propex has a heater marketed to the VW van crowd. Webasto has their AirTop heaters. Neither of these are electric, but they are intended for use in vehicles, such as yours. as far as electric heaters, any Walmart heater will work, as they have do-over switches, overheat switches, and other safety designs. 

I bought a tiny space heater at Walmart to use in my van. Details are here:

https://sandcastle.sandsys.org/2013/01/space-heater/

Although I appear to have not saved the name of the heater itself.

Linda Sand