An example ~ your A/C is running. You are not running in and out and nobody is at home, yet, you don't want to come home to a hot steamy jungle that takes 6 hours to cool that evening. The A/C controller could switch over to a Relative Value of 10 degrees less than outside ambient rather than running on the Absolute Value of 70 degrees.
Your washer/dryer could easily be regulated to deal with variable power requirements depending on humidity levels (hey, mine already does eh).
All of our expensive LED lighting systems could be made even more efficient with simple motion detectors (turning them off when no one is around).
And so forth.
The future is yours:
For $18.97 you can install a programmable thermostat. You can come home to a cool house without paying to cool it all day.
May I suggest a programmable thermostat? If you have any problems with homemade Minnesota designs you could find another brand, but I prefer Honeywell.