Anyone else notice that running the AC gives a SERIOUS hit on gas mileage?

Like, to the tune of 6-7 MPG?

I live in Central Texas where it's not unusual to sit at or around 100degrees Fahrenheit. for weeks/months on end. So running the AC is a must.

I noticed the trend when I stopped running the AC at night when the temps dropped for a while & my MPG improved DRASTICALLY!!!