We recently had regulators (with a very reasonable setting) installed on both our thermostats. Your guests will not even know they are there. Our utilities bills have gone up considerably. But the main reason was that people kept whirling the control all the way down, then leaving doors open or leaving the house. This is a tremendous strain on your a/c system and shortens its life. After spending almost $2K on a new condenser that had to be installed on July 4th for the guests' comfort, we decided to take matters in hand.
Don Walton of Walton Electrical in DeFuniak Springs did our work and we were very pleased. He responded within hours, installed the new condenser the next day (July 4), and did not charge extra for the holiday. The cost was high because it was a very large unit and we had him check the other unit out while he was there.
Oh, the cost of the regulators is about $100 each and you will need one on each of your thermostats. They can regulate both the a/c and the heat.