Is there a way to open the trunk by itself?

When our '10 was new raising the hatch still required a hand, but was close to effortless. The two cylinders that accomplish this have gradually lost oomph. Currently it still goes up, and stays up, with help.

Guessing your '11's cylinders are similar condition, replacement is a simple/effective improvement. Attached is a shopping cart I started with Amayama, for 2011 Prius. Price is $85 CDN apiece, shipping still to be determined. I'd guestimate around $40 CDN.

You could try plugging the part no's into the Toyota USA parts site too:

689500W520
689600W330

 

There are aftermarket kits available

 

You can buy electric lift cylinders then you're going to have to wire them which shouldn't be too too hard and then the hatch will go up by itself You just watch set the groceries down get back in the car push the button and it'll close You have to be careful with this though because you can't have people trying to push down on the hatch you know the ignorant dude that puts the stuff in your car at the grocery store you have to keep an eye on him or you'll have broken lift motors they may be a workaround of the high-end units may have a system in place for that just beware.

 

My daughter look at some custom audio sites some Chinese sites I can't imagine I'd pay $700 for two electric lift struts and a few pieces of wire and a button but yeah I know a lot of people will everything now is motorized or has motorized options in the '80s we were making amp racks and whatnot that were motorized and would lift up and show other equipment and so on and so forth The struts themselves are about 80 or 100 bucks or something like that or they were now I don't know if they've added gold to these things or what exactly happened but when I'm looking at some point now find some pieces I'm not saying it would be made up for the car you need to know the stroke length of the cylinder you want so on and so forth If you want to bolt-on kit yeah then it'll be $700 or something like that then again and till I'm 100 and can't move the hatch this probably won't be a thing and then I won't be driving.