I used a cheapie all last summer at night (free range and in the woods during hot days.) Plus my coop is wire on two sides with a large overhanging roof (actually about half of a 3-sided bldg.) I never saw any sign they were bothered by our heat. In the winter I covered a lot of the wire with plastic.
I used straw for litter last summer and had to replace the fan once or twice when it got overburdened with dust. But I did not pay much for them. I used a box type fan but they were small, maybe 12" on each side. I put the fan where the air would not actually blow across the roost.