Any such leaks should be repaired or filled with caulk, expanding foam or some other insulation.
The thermostat is another place to take action. In the winter, adjusting your thermostat to a slightly lower setting can make a difference. Up to 7% of your heating costs could be avoided for every degree you lower your thermostat. Likewise, turning the thermostat a few degrees higher during the summer means savings.
A clock thermostat which can be set to raise and lower the temperature automatically several times a day, can keep the system from running when it’s not needed. However, heat pump thermostats should be left at one setting.
Another big factor in heating and cooling costs is the efficiency of the system itself. Without proper maintenance and cleaning, even the most energy-efficient system in the world can become an energy waster.
It is advisable to have your system routinely serviced by a qualified HVAC mechanic once a year, but that doesn’t mean there’s nothing you can do to help keep the system in proper working order. Start by making sure none of the registers are blocked or restricted. Then, proceed to the unit itself and check its filter. Estimates show that up to 90% of all HVAC systems have dirty filters, and that could be costing you as much as 20% more than normal to keep your home comfortable. All duct work, whether in attic space or underneath the house, should be well insulated. That is a task that the homeowner can generally complete with no more tools than a good knife and a roll of duct tape.
Finally, the age and efficiency of your system can make a big difference. A 10-year-old system, although it may have been top-of-the-line at that time, could be much less efficient than new HVAC systems.