Remove the existing thermostat for central air units and replace it with a programmable digital thermostat. Digital thermostats come with installation instructions.
Set the thermostat to turn off when the house is normally unoccupied, like work or school days. Have the thermostat turn on approximately 30 minutes before residents return to the house.
Raise the temperature to the maximum setting -- 90 to 95 degrees Fahrenheit -- when leaving the house, if you cannot replace the thermostat. Raising it to the highest level ensures that the AC unit does not activate while you are away.
Turn the thermostat to the desired temperature upon returning to the house.
Install a plug-in timer into the outlet connected to a window unit. Plug-in timers are manually set to specific times to trigger the outlet to turn on and off. Leave the window unit turned on but schedule the plug-in timer to turn off at specific times when the room or house is unoccupied.