You put a gallon milk jug of water, frozen inside and turn the fan on. it's amazing the air coming out is about 50* This cost about $25 because we went with a 12 volt fan. It runs on batteries, solar panel or wall adapter, so will have back up in case of power outage. Regular fans are cheaper. If you want to try building one go to Utube or google and search redneck air conditioner or redneck AC. There are all kinds of designs, some are bigger. Going to build another with high velocity fan and will be using in the chicken coop.