Do you have a basement? Attic fans are really beneficial if you have a basement, as it sucks the cool air up to the 1st/2nd floors.

Do you have multi-floors?

I don't think attic fans are that expensive. It's a quick and easy way to suck the hot air out of the house during the night. You just need to make sure you have adequate ventilation in the attic.

In the summer, I'm not sure you'd use it during the day or with your HVAC. So if the nights are in the 90s+, I wouldn't use it.

IMHO, it's just a good way to cool down a hot house when the temps cool down.

We solely used an attic fan to cool the house and it was useless when temps were very hot at night. It just moved around hot air.