I have lived in my condo for about 3 years now, when my wife and I moved in we had a standard (older model) thermostat, the just small rectanular one with the little livers in the bottom you just clicked left or right for heat or air and left or right to turn on or off. After the first summer we decided to by a new digital thermostat, we hoped it would save with the heating and air bill because we could program it. The area we live in in Central CA gets up to 110 in the summer and the past summer and going into this one it is sooooo miserable now, our condo on some days will get up to 92 degress and our air condition won't cool it down, we can set it at 75 and it won't dip below 90. Today we had all the windows and blinds shut, it hit 94 where we live and our condo got up to 88, I am typing this so late at night because I can't sleep it is so hot. We had a professional hook it up, I'm just wondering, why would it be so much worse with a new thermostat? What should I do?

Sounds to me like the guy didn't hook it up right or else the thermostat is defective.

Make sure the T-stat is in the cool mode and is on Auto. Also, make sure if the T-stat has a electric/gas switch, that it's set in the right position. If your furnace is a gas furnace, then set the switch to gas. That might help.

It is possible that you have a freon leak and are low on freon, did this change take place at the time you changed the thermostat or did it happen over a period.

Let me know and I will try to help you.

I agree with letmetellu, I think you have a bigger problem then the t-stat