Gen 3 Trailer Hitch Cargo Shelf

Yes... I used one once on a Gen2 Prius to haul a 280 pound disassembled woodchipper on a 1700 mile road trip and almost no difference in MPG. But those types of shelves (Hitch Haul) work better with modifications because they come with extra long bars that the shelf sits on for convenience, which is no problem if you're putting one on a truck or big SUV with a big tongue weight, but put one an economy car with a much lower tongue weight and that extra long bar is a big lever that makes the tongue weight way higher. When I hauled my chipper I built a custom mount to shorten the length of the lever as much as possible to reduce tongue weight and have the tarped wrapped packaged touching the bumper cover so there was no movement or gaps. But then then I was in crazy high speed traffic in SF Bay area and had to get up to 75 just to merge into the slowest lane and I hit some slumps in the road and new right away that was bad news. Turns out I bent my hitch receiver down close to a half an inch. So it's very limited in terms of how much weight you can haul unless you reinforce the hitch.

 

i have been looking into these recently as well. i think the weight limit will be much lower than the carrier weight limit, unless you want to upgrade the suspension

 

Not a 3rd generation, but I have a Curt cargo tray and use it to haul stuff with our Prius c.

I've never tried it with more than say, 50lbs of stuff and the trips haven't been that far, but we can't really tell the fuel economy to be any different at least for around-town usage.