Can't find any evidence at all that these things work.
I always wondered if these "Ultrasonic Pest Repellers" actually work.  I guess I have my answer.  At least these particular devices do not.  I had squirrels chewing up cardboard and tarps in a storage shed that has power, so I chose to install one of these to see if they would vacate.  They did not.  Not only that, but I installed the 2nd one at about 15" above my patio under an overhang in an outdoor setting.  I have outdoor cameras that recorded Rabbits and Squirrels hopping right up to within 2 feet of the device, happily looking around and going about their business as if it wasn't there...not  the least "put off" by this device.  They do not seem to care, so I would say save your money.
Rating: 1 stars