HVAC stands for heating, ventilation and air conditioning. It's also shorthand for "Here's my Visa and cash." If you don't properly maintain your furnace and air conditioning units, they could require expensive repairs or die altogether. A gas furnace alone costs between $1,000 and $2,000 at Home Depot, but you'll pay between $4,000 and $8,000 for a professional furnace installation [source: HomeAdvisor].
The best way to avoid a furnace or air conditioner failure is to conduct maintenance on your units every six months. An HVAC professional will come to your home and run through a checklist that includes lubricating all moving parts, tightening electrical connections, clearing out the condensate drain in the air conditioner, checking refrigerant level and cleaning any dirty coils or fixtures [source: Energy Star]. Left alone, any of these issues will lower the efficiency of your system and cause premature wear on components.
Another thing you can do to improve the efficiency and longevity of your HVAC system — plus improve air quality in your home — is to replace the air filter at least once every 90 days. You might want to replace it more frequently if you have allergies or pets. The pros recommend the newer high-efficiency pleated filters [source: Trattner].