Get the right one and they are quite, effective and cost efficient too!
I like designs like these: https://quietcoolsystems.com
It took a couple hours to install, mainly because I went back and forth where to install the intake vent. I had power readily available from a hallway outlet - added a switch above the outlet, carried it up into the attic and to the fan. If you aren't comfortable doing your own wiring that will be the hardest part of installing the fan. The rest is simple - cut a hole in the drywall of your ceiling where you want the intake, mount the insulated box with the insulated dampers that close when the fan is not in use, hang the fan with the proper 90 degree bend in the duct, wire it in and finally snap the grate on and you are done. The only "glitch" I had with my install is I had the fan pointed down a bit too much and my attic has blown in insulation (ugh). The fan ended up blowing a big "hole" in it. So I adjusted the fan, raked the insulation back into place and haven't had an issue since.
My air conditioners each use about 2400 watts each (I have two!), the motor on my whole house fan is around 640 watts. We had an exceptional fall the year I put it in, and it more than paid for itself. And I got the benefits of fresh air. I live in the Mid Atlantic so spring and fall are the biggest time of year I can use it, but this year our summer wasn't too bad with humidity so I used it most of the summer too. It's amazing how much heat you can tolerate if you have a steady breeze.
I highly recommend them! My only complaint is I wish mine had variable speed. There are many times at night it gets way too cold to run at normal speed, but if off the heat of everything in the house will heat the interior back up again without at least some airflow. With the size of my house I need to add a second one anyway to get enough airflow/turn over so I'm thinking about one of their units that has two fans - can run just one for a lower amount of air volume.
One of my best home upgrades, that's for sure!