Simply using your home thermostat by adjusting up when the AC is on and down when the heat is on will save. When not home you can raise up or lower down the temperature. Leaving it on all the time is like running your car when you are not using it. In Europe cars are made to shut off at traffic lights and auto restart when you lift off the brake.
You can operate your home without cost by just adjusting the thermostat when you go to bed at night , get up in morning, leave for work and when you come home at night.