You can save as much as 10% a year on heating and cooling by simply turning your thermostat back 7 to 10 degrees for 8 hours a day from its normal setting. The percentage of savings from setback is greater for buildings in milder climates than for those in more severe climates.
In the summer, keep your house warmer than normal when you are away, and lower the thermostat only when you are at home and need cooling. Set your thermostat at as high a temperature as comfortably possible and ensure humidity control if needed. Any time you are going to be away for several hours, raise the thermostat to save energy.
Although thermostats can be adjusted manually, programmable thermostats will avoid any discomfort by returning temperatures to normal before you wake or return home.
Avoid setting your thermostat at a colder setting than normal when you turn on your air conditioner. It will not cool your home any faster and could result in excessive cooling and, therefore, unnecessary expense.
A common misconception associated with thermostats is that a furnace works harder than normal to warm the space back to a comfortable temperature after the thermostat has been set back, resulting in little or no savings. In fact, as soon as your house drops below its normal temperature, it will lose energy to the surrounding environment more slowly. The lower the interior temperature… the slower the heat loss. So the longer your house remains at the lower temperature, the more energy you save, because your house has lost less energy than it would have at the higher temperature. The same concept applies to raising your thermostat setting in the summer — a higher interior temperature will slow the flow of heat into your house, saving energy on air conditioning.
Find out more at https://energy.gov/energysaver/thermostats.