It's also worth noting that becuase a swamp cooler uses water to cool the air that it tends to increase the ambient humidity in the dwelling whereas air conditioners tends to dry out the air.
If you drive around and see a big louvered box sitting on people's roof; that's a Swamp Cooler.
I uses a mist of water to cool the air that is being blown into the house.
It is better than nothing.
It was installed in a lot of houses in the 60's and there are still a lot of them, because people cannot afford to replace them with A/C units. (All the ducting would have to be re-done too.
With the new, energy efficient A/C units, the difference is probably very little, but the results are world's-apart.