thermostat correctly is critical to achieving comfort and minimising
energy use. Setting the Temperature one degree cooler than needed in
the summer will cause a surprisingly large increase in energy use.
Similarly setting the Temperature one degree warmer than needed in the
winter will also cause a surprisingly large increase in energy use.
Normally it is best to set the temperature at 22 degrees. For most air
conditioners this would give a temperature of around 24 degrees for
most of the summer and 20 degrees for most of the winter. However in
practice there are a number of factors that may require a different
setting. For example if in winter you get cold air next to the windows
sinking down and pooling at floor level, it may be necessary to set
the thermostat at a higher temperature.
Often thermostats are not very accurate; this is not really a problem if you can find a single setting that achieves comfort all year round. Sometimes though, it is necessary to occasionally tweak the setting.
More detail is available from the pdf document 'Getting the most from your refrigerative air conditioner' which is available free if you order one of my air conditioner selectors.