The new huge GM EV & SUV trucks do have way more battery - and weight. The GM Silverado EV Work Truck is EPA 492 miles, tested at 530 by edmonds. So take the common rule of thumb, divide range by half or maybe a little more and you get about 250 miles of towing range. https://news.gm.com/home.detail.html/Pages/topic/us/en/2025/....

In a couple of recent youtube videos, "Aging Wheels" thoroughly tested a variety of trailers towed behind a variety of vehicles and then also added weight to the trailer to see the efficiency impact of towing a trailer with a lot more weight. They found a 4.3% efficiency drop by adding weight to max out the towing, compared to towing without the extra weight. Weight isn't what matters on towing impact, it's the wind resistance of the trailer that matters much more.

They did a long series of comparison drives (in the about 30 mins video) with different trailers and then loaded them with extra weight to see the impact. It was smaller than you expect. The video with all the tests is https://www.youtube.com/watch?v=UmKf8smvGsA.

I heard about this on the batteries included podcast where they interview the author of the video above, and kind of give high level summary with some details, https://www.youtube.com/watch?v=wGJv-xAqcTI.

That first video was very well done, answers so many questions all at once. I’m going to put effort into making my setup much more aerodynamic. That’s a potential 30-50 miles more per charge there!