Anyone have MPG experience with a thule roof cargo carrier on roof rack?

Yes! Mileage goes down.

Here's what I've written on my rack pages:

Treat yourself to not worrying about this, and go enjoy yourself. Next time buy an EV, and worry even less.

 

Excellent. Well, I have plenty of experience with a cargo box. But I still can't answer the question. Depends on so many factors. Assume that you'll get 35 mpg with anything on the roof, and that should cover it. A Cargo box will do about the same for you as an Xmas tree!

On this trip, I drove 2500 miles in this configuration. Total when we got home: 41.

 

BTW, here are my rack pages if you haven't seen them:

Prius Permanent Rack Pads

and the clip-ons:
Prius Clip Racks

And a bunch of stuff I've used the car for:
Prius Utility Vehicle

 

Sounds similar to me. My lifetime average is 51 mpg. And that includes all my trailer-pulling, and cargo-toting, roof-carrying episodes. And THAT is why I tell people to just not sweat it. Yeah, it'll be bad when you're carrying stuff. But you get to bounce right back to normal once to take the stuff off the roof. My rule is that I just never leave the racks or gear on the car unless I'm truly using it.

 

2 "stand up" bikes on roof to rack (ea w both wheels on) w Yakima rack from Boston to the end of Cape Cod (Provincetown) and got ~39 MPG. My normal just before (increasing with the warmer weather) was 52. It's the only way I have just now to get both our bikes around. yea, I figure its way better than the alternative. I always bring my bike to work (for lunchtime rides) inside the car. It's a bit of a pain but worth it. I had noticed a few trips to work with the rack on w/o bikes dropped my MPG (from 52) to 47. Quite a hit on the aerodynamics!
PS: I wonder how much improvement I'd get with the front-wheel-off design of Yakima roof bike racks. A few MPG I guess....Cheers. Don

 

I usually get around 35-38 MPG with my Thule roof-top carrier (which is spacious but wide, not very stream-lined). My lifetime mileage is around 46.2 MPG but closer to 47.0 if I take the hauling trips out of the averages. Picture here on PC somewhere. The cargo box is a great thing to have for the Prius when you need the extra storage space.

 

Looks like you have a canoe on your Prius! This is exactly what my 61-year old parents want to do, but they're worried that the car couldn't lug the canoe around, that the visibility might be bad, and that the handling might be bad. They haven't purchased a Prius yet, so they're looking at the 2012 models, from the tiny little Prius C to the big Prius V. Would you please describe your experience with putting the canoe on top of your Prius?

Thanks in advance!

 

I had no problem with the canoe, it is a 17-ft Grumman aluminum standard about 80-lbs.
I took it on the highway to Eastern Shore of MD. Looks like 45 MPG so not bad.
The first thing you need is a sturdy roof rack, I have the Saris which could hold the space shuttle on there, but is no longer made unfort. Equivalent might be something like the Thule aeroblade. Saris seen here sometimes for sale by prior owner. Then you need to know how to tie down properly, I use the V-shape tie down; there are twists in the middle to prevent back and forth movement. What's nice is there is a lug under each corner for tie downs (on Gen2), prior cars I was always just finding a part or hole in the under frame to tie onto somehow. I drove cautiously as I was worried about my tie down job for sudden stops, as I have not using the canoe much these days.
Someone on Prius Chat recommended a Tarpon 100 10-ft fishing kayak to me, and I am using that all the time now. The idea there it fits inside my minivan so I skip the whole tie down thing and it is only 55-lbs. Next I will be buying kayak holder for the Prius, and may get another Kayak. Canoe just too awkward for me to handle by myself all the time, and if its just me fishing its not optimal anymore.