Some experts say you can save 20 to 40 percent on cooling costs with an upgrade.

The average lifespan of these units is 15 to 20 years, so it may be time to think about a replacement.

If this description fits your HVAC system, then consider buying before disaster strikes during low-demand cooler months. Prices go up for parts, units and service as temperatures rise – and you don’t want to risk a failure in the heat of summer.

What to look for

Be aware of ever-increasing energy costs, checking them on a year-over-year basis per month. You should also be concerned if your repair costs have reached more than half the cost of a new unit. More dust around the home or poorer air quality are signals. Oftentimes, people simply notice that the HVAC system is struggling to keep the home at a comfortable temp. Have a professional evaluate the system itself, while looking for air leaks in the ductwork or home. These leaks can have a huge impact on your unit’s heating and cooling ability.

New advances

Modern HVAC units offer vast improvements, even over counterparts from just a decade ago. In particular, older units use a lot more energy. Some experts say you can save 20 to 40 percent on cooling costs with an upgrade. Look for the Energy Star rating from the U.S. Department of Energy, which certify that these units are some 15 percent more efficient than standard models – a potential difference of hundreds of dollars annually.

Buying a new one

When evaluating new units, look for HVACs that include a Seasonal Energy Efficiency Ratio (or SEER) that’s greater than 11.6, a thermal expansion valve, and variablespeed air handlers. Fan-only switches allow for ventilation at night while reducing your costs. Check-filter lights offer helpful reminders, while an automatic-delay switch will turn off the fan a little while after the compressor stops. Programmable thermostats also offer options that use less energy when you are away.

Before installation

Before installing a new unit:

1. Be sure that there are enough registers to adequately air condition the property – and enough return registers to get enough air back to the system.

2. Insulate attic ducts and seal all leaks.

3. Ensure nothing is blocking airflow to the condensing unit, and that the thermostat is away from heat sources.