[cameldrv]

Most of the energy from driving at highway speeds is coming from aerodynamic drag, and as you say, the Teslas are highly optimized, and the average camper trailer is not really at all. With a gas vehicle this isn't too big of a deal because you only use the camper a couple of times a year, and there are gas stations everywhere, and it only takes a few minutes to fill up.

This suggests to me that there's an emerging business in camper trailers designed for EVs. Make aerodynamics a priority (which also does increase costs and potentially make the living space a less useful shape). There are also trailers starting to emerge that have batteries in them. I've seen some where you can charge the car from the trailer's battery (not sure if they work while the car is moving though), and there are even a couple where the trailers wheels are driven, but I'm not sure how much of that you can really do and keep the vehicle stable.