I have not used my central AC for close to a decade, but this year the heat/humidity got to me. I'm on a three tier electric plan so no AC from 2-7 rate is 18 cents a kw/hr. I keep it at 80 from 7-11 PM and 7 AM till 2 PM, rate 11 c kw/hr. from 11 PM to 7 AM I cool to 78 when the rate is 8 c...