They cool just as well, if not better, because they add humidity to the dryness, and they are a whole lot less to run, electricity-wise. Waaaay less. However, your A/C has an air filter in the return, which cleans the air - if you regularly change it, which you should be doing. A "evaporative cooler" (swamp cooler) does not come with the ability to filter the dust and pet dander from the air, so for the great job it does at a fraction of the cost of the A/C, you have to give up cleaning the air. So, if you have multiple pets with dander, especially birds with powder down, use the A/C. If you only have a dog or two, ones that don't shed massively, or a cat that doesn't shed massively, go for an evaporative cooler on the very hot days. You will still want to use both - one at times and the other at other times so keep your A/C maintained and use the swamp cooler some of the time. We had both for years. Now, we have birds and air cleaners are a must - we have extra, so our swamp cooler has been disconnected.