No, it is generally not more energy efficient to set the air conditioning (AC) at a lower temperature than needed and then turn it off.
Air conditioning systems work by removing heat from the indoor air and cooling it down to the desired temperature. When you set the AC to a lower temperature, it simply makes the system run longer to reach that temperature, but it doesn't cool the space any faster. Keeping the AC running at the desired temperature once it's reached it is typically more energy efficient than turning it off and on.
When you turn off the AC, the temperature inside the space will start to rise. If you let it get too warm, it will take more energy for the AC to cool the space back down to the desired temperature when you turn it on again. Additionally, turning the AC off and on frequently can cause more wear and tear on the system, potentially leading to increased maintenance or repair costs.
To optimize energy efficiency, it's generally recommended to set your AC to the desired temperature and leave it running consistently, adjusting it as needed for comfort. If you want to save energy, you can consider using programmable thermostats or smart AC systems that allow you to set schedules or use occupancy sensors to adjust the temperature automatically when you're not at home or in a particular room.