Reply #3: ok seriously, when we replaced the unit on the roof in PHX and put in a

[NMDemDist2]

programmable thermostat we saved almost half BUT that was a new unit with a 14 SEER rating

with older units, it's important not to let the temp vary too wildly. they aren't as efficient as the new ones and you'll end up spending more trying to bring it back to where you want it than you spent leaving it set at the highest temp you can comfortably stand (78-80 is my range)