Surprisingly quiet: Once it gets going it makes about as much noise as a table fan set on low, if that. Installation is a breeze, and the pre-installed baffles to block the rest of the width of the window make that part very simple: you just pull and you’re done. The panels that overlie the baffles are very easy to place, and make the window look far nicer than other window boxes. The app is very easy to use, and we are extremely pleased with our new air conditioner.