Our central air died last summer and, due to a series of unfortunate events, our budget priorities do not include replacing or repairing it at this point. When we were forecasted for a heat index of 110, I knew that our dogs would probably not survive if we didn't do something. The fans in the house were making it tolerable (not comfortable, but tolerable) for us up until that point, but that was too much.
We also have sliding windows and worried about how we would install a window unit or vent a portable unit. We finally decided on this unit from Sam's Club...
https://www.samsclub.com/sams/12k-portable-ac-inclub-980097924/prod22260007.ip?xid=plp_product_1_1
It came with 2 inserts that fit in the "gap" in the window but our window was actually about 5" taller which left a gap about 5" x 3". It was very easy to simply seal that gap with duct tape.
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(The unit is sitting on a small table, not on the floor. Since our ceilings are so high, we wanted to elevate it to maximize the circulation. We do not have a ceiling fan in this room, but we do have ones in the kitchen and living room. If you have a ceiling fan, you probably would not want to elevate the unit since the ceiling fans would draw the cool air upward.)
It has performed beyond my expectations. I wish we had bought one last year when our A/C died. We have all East/West windows in our house so it can heat up very quickly once the sun comes up and takes a while to cool down in the evening.
We have a "great room" (living room/family room/kitchen) so it's impossible to block it off and isolate a particular area. We set this up in our front room and we have a large fan that blows down the hallways towards the bedrooms. When the peak of the heat wave came through, we "camped out" in the living room because the cool air didn't quite make it down to the bedrooms. That lasted only two nights. Since then, we've had day time temps ranging from the mid-80's to near 100 (we've had it about 2 weeks now) and this unit has been a blessing! It is still "hot" in our house...about 79-82 degrees...but we are comfortable with running a fan or two along with the portable A/C. Once we get our first electric bill after using this new unit, we may consider buying a second one to put in our bedroom. That way, we can "isolate" the hallway and bedrooms and maybe keep them cooler without having to run all of the fans.