Is it cheaper to leave AC on all day?

Is it cheaper to leave AC on all day depends on whether you mean leaving at same temperature all day versus turning off when away, and answer is it is cheaper to leave AC on but raise temperature 7 to 10 degrees when away, not turn off completely or leave at same low temperature all day. Leaving AC at same 72 degrees all day when you are away at work for 8 hours wastes energy cooling empty home, costing more, about 10 to 15 dollars extra per day in hot climate. Turning AC completely off when away causes home to heat up to 85 to 90 degrees, with walls and furniture storing heat, so when you return, AC must run continuously for 3 to 5 hours to remove heat from structure, using more energy than if you had left it at higher setpoint, plus humidity rises to 70 percent encouraging mold. Best practice for savings is to use programmable thermostat to set AC 7 to 10 degrees higher when away, for example set to 78 to 80 degrees when away and 74 to 75 degrees when home, this saves 10 percent on cooling costs per DOE and prevents extreme heat buildup. Using smart thermostat like Nest or Ecobee that learns schedule saves most. For variable speed AC like Trane XV20i, leaving on at constant temperature is more efficient than on-off cycling because variable runs at low speed most efficiently. For most homes, setback strategy saves 100 to 300 dollars per year.