There is no mandatory setpoint for every home. The U.S. Department of Energy recommends using the highest temperature that remains comfortable and adjusting settings when the home is unoccupied.
Start with comfort and humidity
A dry climate and a humid climate can feel very different at the same temperature. If the house is cool but clammy, the issue may be moisture removal rather than an excessively high setpoint.
Make small changes
Raise the setting a degree, wait, and evaluate. Gradual changes reveal the comfort threshold without creating unnecessary large recovery cycles.
Use fans where people are present
Air movement improves perceived comfort and can allow a slightly higher thermostat setting. Turn fans off in empty rooms.
Do not compensate for a hot house with an extremely low setting
Most air conditioners do not cool faster because you select a much lower temperature; they simply run longer trying to reach it.
If the system cannot reach a reasonable setpoint, diagnose the problem
A dirty filter, blocked outdoor unit, open doors, strong solar gain, or equipment fault can prevent normal performance. Lowering the thermostat further does not fix those causes.
The practical summer setting is the highest one that maintains acceptable comfort and humidity for the people in the home, with sensible adjustments when nobody is there.
Sources
- U.S. Department of Energy — Air Conditioning — Air-conditioning efficiency, thermostat strategy, maintenance, and cooling-load reduction.